Subject: Carbon Arc Lighting and how to make electrodes
Sent: 7 July 05

Over all Summary:

Using hard graphite carbon rods (made like pencil leads) and a voltage of 45 to 
60 volts with about 2 to 10 amps DC in a Simi closed environment (behind glass, 
with controlled air flow) consumes the least amount of carbon rod.  DC work best 
but AC can be used.  Current is limited by use of resistor (DC) or Inductance 
(Ac).  This is necessary because of the negative resistance characteristic of 
the arc.  

The electrodes when in use need to be in a slow continuous motion toward each 
other in order to maintain a given arc length and to compensate for the carbon 
burned up. All kinds of electro-mechanical setups are possible. Hissing of the 
arc indicates electrodes are too close or too much current.  Carbon electrodes 
are classified as molded carbons and forced carbons depending on how they are 
manufactured.  Forced carbons are higher quality then molded carbons. Good 
electrodes of average size average about .15 ohm/foot. Positive electrode is 
consumed twice as fast as the negative.  

Electrodes can be made from other types of carbon (petroleum coke, charcoal, 
certain types of coal, lampblack and carbon black from oil or natural gas) but 
it is not easy or likely in a primitive environment.  Self-baking electrodes are 
used a lot in electric furnaces used to refined metals.  The technique has 
promise if it can be setup see patents on this subject. 

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Note: I promised Nancy a few years ago I would look into this subject. Every 
time I picked up the subject up to research I ran into a brick wall of 
complexity with much development done in the past that had dived out of site and 
was not readily available.  Finally after much looking... I realized this was 
not going to be something the normal primitive survival person would be able to 
accomplish.  In other words it took until nearly modern times to develop the 
processes and techniques to make these electrodes.  It is as much an art as it 
is an engineering effort at extremely high temperatures and currents.  I tried 
several experiments at making electrodes from ground up charcoal to no avail. 
They would not conduct electricity. I couldn't get them hot enough and compacted 
enough in a no air environment to make a graphitized conducting electrode.  

I think if one has naturally occurring graphite available then it might be 
possible using the pencil making technique. This would be to fine grind the 
graphite and 5-10% clay and water, then heated to fuse clay making an electrode.  
See write up on making pencil leads.  If one can find big enough graphite chunks 
use them as-is for electrodes.  The highlights of what I found are attached 
below. For more information see the all the patents and reference materials 
included in the primitive survival CD-ROM set. 

The following goes into more detail on the possibilities and techniques.


---------------- 

Electrode making details from reference material:

A small amount of cerium (rare-earth group) is used in a core of a carbon 
electrode to make the light output stronger in the visible spectrum.  Normally 
carbon by it’s self is stronger in the ultraviolet region.  If carbons having 
cores made up a number of metals, among them iron, nickel and aluminum are used 
it results in a minimum visible light and high production of ultraviolet light. 
This is from a book called Illumination engineering. 

Artificial Manufacture of Graphite. The alteration of carbon at high 
temperatures into a material resembling graphite has long been known. In 1893 
Girard and Street patented a furnace and a process by which this transformation 
could be effected. Carbon powder compressed into a rod was slowly passed through 
a tube in which it was subjected to the action of one or more electric arcs. E. 
G. Acheson, in 1896, patented an application of his carborundum process to 
graphite manufacture, and in 1899 the International Acheson Graphite Co. was 
formed, employing electric current from the Niagara Falls. Two procedures are 
adopted: (1) graphitization of molded carbons; (2) graphitization of anthracite 
en masse. The former includes electrodes, lamp carbons, sc. Coke, or some other 
form of amorphous carbon, is mixed with a little tar, and the required article 
moulded in a press or by a die. The articles are stacked transversely in a 
furnace, each being packed in granular coke and covered with carborundum. At 
first the current is 3000 amperes at 220 volts, increasing to 9000 amperes at 20 
volts after 20 hours. In graphitizing en masse large lumps of anthracite are 
treated in the electric furnace. A soft, unctuous form results on treating 
carbon with ash or silica in special furnaces, and this gives the so-called 
"deflocculated" variety when treated with gallotannic acid. These two 
modifications are valuable lubricants. The massive graphite is very easily 
machined and is widely used for electrodes, dynamo brushes, lead pencils and the 
like.
see http://encyclopedia.jrank.org/GOA_GRA/GRAPHITE.html

Gas carbon is produced by the destructive distillation of coal in the 
manufacture of illuminating gas (see Gas: Manufacture), being probably formed by 
the decomposition of gaseous hydrocarbons. It is a very dense form of carbon, 
and is a good conductor of heat and electricity. It is used in the manufacture 
of carbon rods for arc lights, and for the negative element in the Bunsen
battery. see 
http://encyclopedia.jrank.org/CAL_CAR/CARBON_symbol_C_atomic_weight_.html

-----------------

Patent research:

The fourth manufacturing method of a carbon material for a negative electrode 
comprises the steps of applying a heat treatment to a carbonaceous material 
containing at least one material selected from the group consisting essentially 
of the carbonized material and the graphitized material under a gaseous 
atmosphere selected from the group consisting of a first gaseous atmosphere 
containing at least 10% by volume of CO.sub.2, a second gaseous atmosphere 
containing at least 1% by volume of H.sub.2 O and a third gaseous atmosphere 
containing at least 10% by volume of CO.sub.2 and at least 1% by volume of 
H.sub.2 O, and bringing the carbonaceous material into contact with a gaseous 
acid.

It is desirable to apply a heat treatment to the carbonaceous material in order 
to maintain a gaseous state of the acid when the gaseous acid is brought into 
contact with the carbonaceous material having the heat treatment applied 
thereto. It is desirable for the heat treating temperature to fall within a 
range of between the vaporizing temperature of the inorganic acid or organic 
acid and 800.degree. C. If the heat treating temperature exceeds 800.degree. C., 
the reaction proceeds rapidly, with the result that it is possibly difficult to 
apply a uniform acid treatment to the surface of the carbonaceous material. It 
is more desirable for the heat treating temperature to fall within a range of 
between the vaporizing temperature of the inorganic acid or the organic acid and 
500.degree. C. Where, for example, nitric acid is used as the inorganic acid, it 
is desirable for the heat treating temperature to fall within a range of between 
130.degree. C. and 500.degree. C.

One of 30 sample methods was prepared by spinning a petroleum pitch used as a 
carbon precursor, followed by applying a heat treatment to the spun sample at 
300.degree. C. for one hour so as to make the spun sample infusible. Then, a 
heat treatment was applied to the carbon precursor at 900.degree. C. for 3 hours 
in the presence of an atmosphere gas consisting of 100% by volume of a carbon 
dioxide gas so as to obtain a carbonized material. The carbonized material thus 
obtained belonged to an amorphous carbon or a soft carbon. Further, a heat 
treatment was applied to the carbonized material at 2800.degree. C. for 3 hours 
in the presence of an atmosphere gas consisting of 100% by volume of a carbon 
dioxide gas so as to obtain a fibrous carbon material. Before the heat 
treatment, an atmosphere gas was introduced into the furnace so as to completely 
substitute the gas within the furnace, followed by stopping the gas supply and 
subsequently starting the heat treatment. 

The average particle diameter, the interplanar spacing d.sub.002 derived from 
(002) reflection, which was determined by the X-ray diffractometry, the specific 
surface area determined by the BET method, and the immersion heat ratio 
.DELTA.H.sub.i.sup.n /.DELTA.H.sub.i.sup.h of the carbon material were measured 
under the conditions equal to those employed in Example 24 in respect of the 
carbon material thus obtained. Table 8 shows the results. 6,623,889 23 Sep 2003
Various processes have been developed over the years for the production of high 
performance carbon fiber materials. One of the leading processes for producing 
high performance carbon fibers is the so-called PAN process wherein 
polyacrylonitrile is used as a precursor fiber. The PAN process typically starts 
with a highly prestretched PAN fiber and involves three steps. First is a 
stabilization treatment wherein the PAN fiber is heat treated in air at a 
temperature from about 200.degree. to 300.degree. C. for one or more hours. In 
the second step, the fiber is carbonized at a temperature above about 
1100.degree. C. in a non-oxidizing atmosphere. Last is a post heat treatment at 
temperatures up to about 2500.degree. C. to graphitize the fiber and give it 
high performance properties. It is in this post heat treatment step that the 
chemical composition, the crystalline structure, and the mechanical properties 
are strongly influenced. 

There has been an intense effort to develop methods of spinning and carbonizing 
hydrocarbon pitch fiber to reduce precursor filament cost and weight loss. 
However, such processes require pitch pretreatment, spinning conditions, and 
post-treatments to insure correct orientation of carbon atoms in the final 
products. As a result, use of spun and carbonized hydrocarbon pitch has been 
nearly as expensive as using the previously noted methods involving organic 
polymers. Both methods require use of continuous filaments to achieve high 
orientation and good properties. There is a practical fiber diameter lower limit 
of 6 to 8 micrometers. Thinner fibers break during spinning and require 
excessive post-treatment.  

Above is from patent: 5,643,670 date: July 1, 1997


This fine carbon power is required to have properties comparable to normal 
graphite powder, more specifically, good electrical conductivity as an electrode 
and in the case of a battery, electrical or chemical properties such that the 
carbonaceous member is resistant against a corrosion by an acid. 

Carbon black is a material having properties satisfying these requirements to a 
certain extent and is used over a wide range. In general, carbon commonly 
obtained from coke is graphitized, for example, by heating at a high temperature 
with an attempt to stabilize chemically and improve the corrosion resistance. 
However, carbon black is a material difficult to graphitize and can be hardly 
graphitized by mere heating. 

Therefore, for example, JP-A-62-246813 (the term "JP-A" as used herein means an 
"unexamined published Japanese patent application") discloses a technique of 
adding boric acid to carbon black and heating the obtained slurry at a 
temperature of 1,000 to 2,000.degree. C. to reduce the d.sub.002 of carbon 
crystal, which is an index of showing the graphitization, even to 3.41 .ANG. 
(0.341 nm), thereby attaining the graphitization. However, according to the 
study by the present inventors, d.sub.002 of carbon black cannot be lowered to 
less than 3.40 .ANG. which is by far larger than the theoretical value for 
complete graphite (i.e. 3.354 A). Furthermore, mere heating for the 
graphitization fails in elevating the electrical conductivity as demanded. 

Therefore the first object of the present invention is to obtain graphitized 
fine carbon powder having excellent crystallinity and thereby increased in the 
resistance against chemical corrosion and at the same time, improved in the 
electrical conductivity, and to provide a high performance catalyst for polymer 
electrolyte fuel battery and polymer electrolyte fuel battery using the 
catalyst.

As a result of extensive investigations by taking account of the above-described 
problems, the present inventors have found that by using carbon black that was 
considered to be hardly graphitized, submicron fine graphitized carbon powder 
having an X-ray plane spacing C.sub.0 value (double of d.sub.002) of less than 
0.680 nm (namely, d.sub.002 is less than 3.40 .ANG.) can be obtained. 
Furthermore the present inventors succeeded to obtain a high-performance fuel 
battery by using the powder as a catalyst support for fuel battery.

12. The electrically conducting carbon composite powder for supporting a 
catalyst as described in 11 above, wherein from 1 to 7% by mass of vapor grown 
carbon fiber is mixed with carbon powder. 

13. The electrically conducting carbon composite powder for supporting a 
catalyst as described in any one of 10 to 12 above, wherein the carbon powder is 
heat-treated at a temperature of 2,500.degree. C. or more. 

14. The electrically conducting carbon composite powder for supporting a 
catalyst as described in any one of 11 to 13 above, wherein the vapor grown 
carbon fiber is graphitized at a temperature of 2,500.degree. C. or more and 
boron content in the fiber is in a range of 0.001 to 5% by mass.

DETAILED DESCRIPTION OF THE INVENTION 

To begin with, the first group of the present invention: fine graphitized carbon 
powder having good crystallinity, production method thereof, an electrically 
conducting carbon composite powder for supporting a catalyst using the carbon 
powder, a catalyst for polymer electrolyte fuel battery, polymer electrolyte 
fuel battery cell, and polymer electrolyte fuel battery, will be described in 
detail below. 

The raw material used for obtaining the carbon powder of the present invention 
is a submicron fine particle comprising an amorphous carbonaceous material 
called carbon black. Examples of the carbon black include oil furnace black 
(e.g., Ketjen Black, Valcan, both are trade names) obtained by incompletely 
combusting aromatic hydrocarbon oil such as creosote oil; acetylene black (e.g., 
Denka-Black, trade name) obtained by complete combusting method using acetylene 
as a raw material; thermal black obtained by complete combusting method using 
natural gas as a raw material; and channel black obtained by incomplete 
combusting method using natural gas as a raw material. Any of these can be used. 

Among these carbon blacks, oil furnace black and acetylene black are preferred. 

The reasons that the two are preferred are explained as follows. One of 
important factors determining the performance of carbon black as an electrically 
conducting material is a primary particle chain structure (aggregation 
structure) called structure. The structure of carbon black have generally this 
aggregation structure where fine spherical primary particles are gathered and 
form irregular chained branches. As the number of primary particles is larger 
and as the chained branches are more complicated (called high structure state), 
the effect of imparting electrical conductivity is higher. This high structure 
state can be easily formed in the oil furnace black and acetylene furnace black 
and therefore, these carbon blacks are preferred. 

The carbon powder of the present invention can preferably contain boron. This 
carbon powder containing boron can be produced, for example, carbon black and 
boron compound such as boron carbide (B.sub.4 C), boron oxide and boron nitride 
are mixed, and the mixture is heat-treated at 2,500.degree. C. or more in a non-
oxidative atmosphere. 

Among these methods, one preferable method where the carbon black is mixed with 
boron carbide (B.sub.4 C) and heated at a high temperature, that is not 
described in a literature, is explained below. 

The boron carbide is ground to a particle size of 40 .mu.m or less and then 
mixed with carbon black. The average particle size of boron carbide is 
preferably 20 .mu.m or less. If the average particle size exceeds this range, 
the effect by the addition is small and also the yield and productivity 
decrease. 

In the grinding, a commercially available general impact-type grinder (e.g., 
roller mill, ball mill, pulverizer) can be used. The boron carbide is difficult 
to grind and therefore, is preferably ground in advance to the mixing with 
carbon black. 

The amount of boron carbide added is suitably from 0.01 to 7% by mass, 
preferably from 0.5 to 7% by mass as calculated in terms of boron. If the amount 
added is less than this range, the graphitization barely proceeds, whereas even 
if the amount added exceeds 7% by mass, the graphitization does not proceed any 
more and this is useless. The boron added in this range comes to be present in 
the carbon powder in an amount of 0.001 to 5% by mass, preferably 0.1 to 5% by 
mass and by virtue of this, the above-described graphitization effect can be 
brought out. 

The boron carbide and carbon black may be mixed by any method without using any 
special machine as long as these are uniformly mixed. 

The mixture of carbon black and boron carbide is preferably placed in a 
graphitic container and heat-treated in a non-oxidative atmosphere by passing an 
inert gas such as argon. The heat-treatment temperature must be 2,500.degree. C. 
or more. If the temperature is less than this range, the graphitization does not 
proceed and the graphitic fine carbon powder having a plane spacing of a unit 
lattice (C.sub.0 value) of less than 0.680 nm, furthermore 0.6730 nm or less for 
use in the present invention cannot be obtained. 

The heat-treatment furnace for the graphitization may be any furnace as long as 
the heat-treatment can be performed at a desired temperature in a non-oxidative 
atmosphere and for example, an Acheson furnace utilizing carbon powder particles 
for the heat generation, a high frequency furnace and a furnace using a solid 
graphite heating element may be used. The non-oxidative atmosphere can be 
obtained by burying the material to be graphitized in the carbon powder or 
purging the inside of the furnace with an inert gas such as nitrogen gas or 
argon gas. 

In the heating, after the entire material to be heated reaches a predetermined 
temperature, holding for a certain time is not particularly necessary. The heat-
treated material is allowed to cool in the same non-oxidative atmosphere and 
ground by lightly stirring it. 

If a boric acid which is in general easily available is mixed and heat-treated, 
instead of using boron carbide as the raw material of boron, enough reduction in 
the C.sub.0 value cannot be attained by the graphitization, and it is difficult 
to make the C.sub.0 value of less than 0.680 nm. 

By the above-described method of the present invention, carbon black which is 
said usually non-graphitizable and difficult to graphitize, can be graphitized. 

When the carbon fine powder of the present invention is measured by an X ray, 
the C.sub.0 crystallite plane spacing (double of d.sub.002) generally used as an 
index for showing the graphitization degree is less than 0.680 nm, furthermore 
0.6730 nm or less. C.sub.0 value as low as this level can not be attained using 
the submicron carbon powder. 

The fine carbon powder of the present invention uses carbon black having a 
primary particle size of about several nm to about 100 nm as the raw material 
and is obtained by the partial aggregation of the carbons and therefore, after 
the graphitization, the particles having this primary particle size are 
aggregated as they are. 

Even after the heat-treatment and grinding, the aggregated particles are 
estimated to have almost the same average particle size and distribution as 
those before the heat-treatment. 

The primary particle size can be directly measured by the observation through 
TEM (transmission electron microscope), but the particle size distribution is 
mostly fixed by the manufacturing standard of carbon black. In the present 
invention, carbon powder having a primary particle size of 100 nm or less is 
suitably used and the graphitization product thereof also has a primary particle 
size within this range. N.sub.2 absorption specific surface area (BET), which is 
decreased by graphitization, is preferably in a range of 50 to 400 m.sup.2 /g in 
the present invention. 

The particle size of the aggregated particle cannot be precisely measured 
because of the aggregation form such that primary particles are branched. When 
the average particle size is measured, for example, by the centrifugal 
precipitation method, the aggregated particles of the present invention are 
considered to be submicron particles having an average particle size of less 
than 1 .mu.m. 

Since the fine carbon powder of the present invention is heat-treated together 
with boron carbide, the graphitization can successfully proceed and the 
electrical conductivity can be improved as compared with ordinary carbon powder 
which is not subjected to a heat-treatment or subjected to a heat-treatment by 
not adding boron carbide.

Above is From Patent#: 6,780,388 B2 Date: 24 Aug 04


Coating for carbon electrodes can consist of 50% by weight of finely ground 
graphite and silica.  Hardened in a furnace.

Casting electrodes: mix ground coke with coal tar. Pressurize at 60-140 deg C 
(plastic paste) and using continuous jolts or vibration to increase density. 
Then baking it for several hours up to a temperature of about 1500 deg C.  

A paste mixture of carbon coal particles fired to the point of Graphitizing the 
Agglomerated Carbon particles. 

Heat the carbon particles first to drive off vapors then mix with binder. 
Important that each particle is coated with the binder. Ground up petroleum coke 
and pitch coke to about .3mm or smaller then separated and the larger particles 
mixed with the pitch (tar) first and the smaller second until it makes a dense 
paste that still wets the full surface of each practical.  

Above is from Patent#: 2,645,583


Bake carbon electrodes used in electric furnaces consist of calcined petroleum 
coke other cokes, charcoal, certain types of coal and lampblack.  They are all 
amorphous carbon structure. The binders are petroleum pitch which is the residue 
of the refining of an asphalt-base petroleum, other pitches and various tars.  
Other binders include molasses, resins, turpentine and various products which 
are produced by distilling organic substances. The volatile material is largely 
eliminated by the baking process.  The residue left consists of elemental carbon 
which bonds the particles of the body material.  All binders are designated as 
carbonaceous.

Old method: petroleum coke is crushed and calcined and the resultant carbon body 
material is ground and this is mixed with the warm binder, which is in the form 
of small particles. This mixture is cooled crushed and ground to produce the 
electrode-forming composition. The ground electrode-forming composition is 
heated in a mold until it becomes pasty.  The mold is then removed from the 
heating oven, and the material in the mold is subjected to high pressure while 
still in the mold. The molded shape is then removed from the mold and is baked 
in a furnace, with the exclusion of air, in order to remove the volatile matter. 
Due to the low thermal conductivity of the molded shape, the baking process 
requires great care, and the finished electrodes are often warped and have low 
conductivity and low mechanical strength due to improper baking. Also, a long 
baking period of one to two weeks is required, especially if the electrode is 
large size. Also, a long cooling period of the furnace is required. The maximum 
temperature of the furnace is about 1050° C. in a gas-fired furnace. 

Above is from Patent# 2,764,539

-------------------------------------------------  
 
Carbon Arc Lighting and making of electrodes -- a good general write up:
See http://encyclopedia.jrank.org/LEO_LOB/LIGHTING.html

The electric arc may be produced between any conducting materials maintained at 
different potentials, provided that the source of electric supply is able to 
furnish a sufficiently large current; but for illuminating purposes pieces of 
hard graphitic carbon are most convenient. If some source of continuous electric 
current is connected to rods of such carbon, first brought into contact and then 
slightly separated, the following facts may be noticed: With a low electromotive 
force of about 50 or 6o volts no discharge takes place until the carbons are in 
actual contact, unless the insulation of the air is broken down by the passage 
of a small electric spark. When this occurs, the space between the carbons is 
filled at once with a flame or luminous vapor, and the carbons themselves become 
highly incandescent at their extremities. If they are horizontal the flame takes 
the form of an arch springing between their tips; hence the name arc. This 
varies somewhat in appearance according to the nature of the current, whether 
continuous or alternating, and according as it is formed in the open air or in 
an enclosed space to which free access of oxygen is pre-vented. Electric arcs 
between metal surfaces differ greatly in color according to the nature of the 
metal. When formed by an alternating current of high electromotive force they 
resemble a lambent flame, flickering and producing a some-what shrill humming 
sound.

Electric arcs may be classified into continuous or alternating current arcs, and 
open or enclosed arcs, carbon arcs with prior chemically impregnated carbons, or 
so-called flame arcs, and arcs formed with metallic or oxide electrodes, such as 
magnetite. A continuous current arc is formed with an electric current flowing 
always in the same direction; an alternating current arc is formed with a 
periodically reversed current. An open arc is one in which the carbons or other 
material forming the arc are freely exposed to the air; an enclosed arc is one 
in which they are included in a glass vessel. If carbons impregnated with 
various salts are used to color or increase the light, the arc is called a 
chemical or flame arc. The carbons or electrodes may be arranged in line one 
above the other, or they may be inclined so as to project the light downwards or 
more in one direction. In a carbon arc if the current is continuous the positive 
carbon becomes much hotter at the end than the negative, and in the open air it 
is worn away, partly by combustion, becoming hollowed out at the extremity into 
a crater. At the same time the negative carbon gradually becomes pointed, and 
also wears away, though much less quickly than the positive. In the continuous-
current open arc the greater part of the light proceeds from the highly 
incandescent positive crater. When the arc is examined through dark glasses, or 
by the optical projection of its image upon a screen, a violet band or stream of 
vapor is seen to extend between the two carbons, surrounded by a nebulous golden 
flame or aureole. If the carbons are maintained at, the right distance apart the 
arc remains steady and silent, but if the carbons are impure, or the distance 
between them too great, the true electric arc rapidly changes its place, 
flickering about and frequently becoming extinguished; when this happens it can 
only be restored by bringing the carbons once more into contact. If the current 
is alternating, then the arc is symmetrical, and both carbons possess nearly the 
same appearance. If it is enclosed in a vessel nearly air-tight, the rate at 
which the carbons are burnt away is greatly reduced, and if the current is 
continuous the positive carbon is no longer cratered out and the negative no 
longer so much pointed as in the case of the open arc.

Davy used for his first experiments rods of wood charcoal which had been heated 
and plunged into mercury to make them better conductors. Not until 1843 was it 
carbons. Proposed by J. B. L. Foucault to employ pencils cut from the hard 
graphitic carbon deposited in the interior of gas retorts. In 1846 W. Greener 
and W. E. Staite patented a process for manufacturing carbons for this purpose, 
but only after the invention of the Gramme dynamo in 187o any great demand arose 
for them. F. P. E. Carle in France in 1876 began to manufacture arc lamp carbons 
of high quality from coke, lampblack and syrup. Now they are made by taking some 
specially refined form of finely divided carbon, such as the soot or lampblack 
formed by cooling the smoke of burning paraffin or tar, or by the carbonization 
of organic matter, and making it into a paste with gum or syrup. This carbon 
paste is forced through dies by means of a hydraulic press, the rods thus formed 
being subsequently baked with such precautions as to preserve them perfectly 
straight. In some cases they are cored, that is to say, have a longitudinal hole 
down them, filled in with a softer carbon. Sometimes they are covered with a 
thin layer of copper by electro-deposition. They are supplied for the market in 
sizes varying from 4 to 30 or 40 millimeters in diameter, and from 8 to 16 in. 
in length. The value of carbons for arc lighting greatly depends on their purity 
and freedom from ash in burning, and on perfect uniformity of structure. For 
ordinary purposes they are generally round in section, but for certain special 
uses, such as lighthouse work, they are made fluted or with a star-shaped 
section. The positive carbon is usually of larger section than the negative. For 
continuous-current arcs a cored carbon is generally used as a positive, and a 
smaller solid carbon as a negative. For flame arc lamps the carbons are 
specially prepared by impregnating them with salts of calcium, magnesium and 
sodium. The calcium gives the best results. The rod is usually of a composite 
type. The outer zone is pure carbon to give strength, the next zone contains 
carbon mixed with the metallic salts, and the inner core is the same but less 
compressed. 

In addition to the metallic salts a flux has to be introduced to prevent the 
formation of a non-conducting ash, and this renders it desirable to place the 
carbons in a downward pointing direction to get rid of the slag so formed. 
Bremer first suggested in 1898 for this purpose the fluorides of calcium, 
strontium or barium. When such carbons are used to form an electric arc the 
metallic salts deflagrate and produce a flame round the arc which is strongly 
colored, the object being to produce a warm yellow glow, instead of the somewhat 
violet and cold light of the pure carbon arc, as well as a greater emission of 
light. As noxious vapors are however given off, flame arcs can only be used out 
of doors. Countless researches have been made on the subject of carbon 
manufacture, and the art has been brought to great perfection. Special manuals 
must be consulted for further information (see especially a treatise on Carbon 
making for all electrical purposes, by F. Jehl, London, 1906).

The physical phenomena of the electric arc are best examined by forming a carbon 
arc between two carbon rods of the above description, held in line in a special 
apparatus, and arranged so as to be capable of being moved to or from each other 
with a slow and easily regulated motion. An arrangement of this kind is called a 
hand-regulated arc lamp (fig. 4). If such an arc lamp is connected to a source 
of electric supply having an electromotive force preferably of 100 volts, and if 
some resistance is included in the circuit, say about 5 ohms, a steady and 
continuous arc is formed when the carbons are brought together and then slightly 
separated. Its appearance may be most conveniently examined by projecting its 
image upon a screen of white paper by means of an achromatic lens. A very little 
examination of the distribution of light from the arc shows that the 
illuminating or candle-power is not the same in different directions. If the 
carbons are vertical and the positive carbon is the upper of the two, the 
illuminating power is greatest in a direction at an angle inclined about 40 or 
50 degrees below the horizon, and at other directions has different values, 
which may be represented by the lengths of radial lines drawn from a centre, the 
extremities of which define a curve called the illuminating curve of the arc 
lamp (fig. 5). Considerable differences exist between the forms of the 
illuminating-power curves of the continuous and alternating current and the open 
or enclosed arcs. 

It will be found that, beginning at the lowest current capable of forming a true 
arc, the potential difference of
the carbons (the arc P.D.) decreases as the current increases. Up to a certain 
current strength the arc is silent, but at a particular critical value P.D. 
suddenly drops about 10 volts, the current at the same time rising 2 or 3 
amperes. At that moment the arc begins to hiss, and in this hissing condition, 
if the current is still further increased, P.D. remains constant over wide 
limits. This drop in voltage on hissing was first noticed by A. Niaudet (La 
Lumiere electrique, 1881, 3, p. 287). It has been shown by Mrs Ayrton (fount. 
Inst. Elec. Eng. 28, 1899, p. 400) that the hissing is mainly due to the oxygen 
which gains access from the air to the crater, when the latter becomes so large 
by reason of the increase of the current as to overspread the end of the 
positive carbon. According to A. E. Blondel and Hans Luggin, hissing takes place 
whenever the current density becomes greater than about 03 or o5 ampere per 
square millimeter of crater area.

It will thus be seen that the arc, considered as a conductor, has the property 
that if the current through it is increased, the difference of potential between 
the carbons is decreased, and in one sense, therefore, the arc may be said to 
act as if it were a negative resistance. 

Violle also, in 1893, supported the opinion that the brightness of the crater 
per square millimeter was independent of the current density, and from certain 
experiments and assumptions as to the specific heat of carbon, he asserted the 
temperature of the crater was about 350o C. It has been concluded that this 
constancy of temperature, and therefore of brightness, is due to the fact that 
the crater is at the temperature of the boiling-point of carbon.

As the current can be interrupted for a moment without extinguishing the arc, it 
is possible to work the electric arc from an alternating current generator 
without apparent intermission in the light, provided that the frequency is not 
much below 50. 

If a continuous-current electric alternating-current arcs is formed in the open 
air with a positive carbon having a diameter of about 15 millimetres, and a 
negative carbon having a diameter of about 9 millimetres, and if a current of 10 
amperes is employed, enclosed the potential difference between the carbons is 
generally from 40 to 50 volts. Such a lamp is therefore called a S00-watt arc. 
Under these conditions the carbons each burn away at the rate of about 1 in. per 
hour, actual combustion taking place in the air which gains access to the 
highly-heated crater and negative tip; hence the most obvious means of 
preventing this disappearance is to enclose the arc in an air-tight glass 
vessel. Such a device was tried very early in the history of arc lighting. The 
result of using a completely air-tight globe, how-ever, is that the contained 
oxygen is removed by combustion with the carbon, and carbon vapor or hydrocarbon 
compounds diffuse through the enclosed space and deposit themselves on the cool 
sides of the glass, which is thereby obscured. It was, however, shown by L. B. 
Marks (Electrician 31, p. 502, and 38, p. 646) in 1893, that if the arc is an 
arc formed with a small current and relatively high voltage, namely, 8o to 85 
volts, it is possible to admit air in such small amount that though the rate of 
combustion of the carbons is reduced, yet the air destroys by oxidation the 
carbon vapor escaping from the arc. An arc lamp operated in this way is called 
an enclosed arc lamp (fig. 8). The top of the enclosing bulb is closed by a gas 
check plug which admits through a small hole a limited supply of air. The 
peculiarity of an enclosed arc lamp operated with a continuous current is that 
the carbons do not burn to a crater on the positive tip or mushroom on the 
negative, but preserve nearly flat surfaces. This feature affects the 
distribution of the light. The illuminating curve of the enclosed arc, 
therefore, has not such a strongly marked maximum value as that of the open arc, 
but on the other hand the true arc or column of incandescent carbon vapor is 
less steady in position, wandering round from place to place on the surface of 
the carbons. As a compensation for this defect, the combustion of the carbons 
per hour in commercial forms of enclosed arc lamps is about one-twentieth part 
of that of an open arc lamp taking the same current.


For the purpose of public illumination it is very usual to employ a lamp taking 
10 amperes, and therefore absorbing about 500 watts. Such a lamp is called a 
500-watt arc lamp, and it is found that a satisfactory illumination is given for 
most street purposes by placing 5oo-watt arc lamps at distances varying from 40 
to l00 yds., and at a height of 20 to 25 ft. above the roadway. The maxi-mum 
candle-power of a 5oo-watt arc enclosed in a roughened or ground-glass globe 
will not exceed 1500 candles, and that of a 6.8-ampere arc (continuous) about 
900 candles. If, how-ever, the arc is an enclosed arc with double globes, the 
absorption of light would reduce the effective maximum to about 200 c.p. and 120 
c.p. respectively. 

One early devised form of arc-lamp mechanism was a system of clock-work driven 
by a spring or weight, which was started and stopped by the action of an 
electromagnet; in modern lighthouse lamps a similar mechanism is still employed. 
W. E. Staite (1847), J. B. L. Foucault (1849), V. L. M. Serrin (1857), J. 
Duboscq (1858), and a host of later inventors, devised numerous forms of 
mechanical and clock-work lamps. The modern self-regulating type may be said to 
have been initiated in 1878 by the differential lamp of F. von Hefner-Alteneck, 
and the clutch lamp of C. F. Brush. The general principle of the former may be 
explained as follows: There are two solenoids, placed one above the other. The 
lower one, of thick wire, is in series with the two carbon rods forming the arc, 
and is hence called the series coil. Above this there is placed another solenoid 
of fine wire, which is called the shunt coil. Suppose an iron rod to be placed 
so as to be partly in one coil and partly in another; then when the coils are 
traversed by currents, the iron core will be acted upon by forces tending to 
pull it into these solenoids. If the iron core be attached to one end of a 
lever, the other end of which carries the upper carbon, it will be seen that if 
the carbons are in contact and the current is switched on, the series coil alone 
will be traversed by the current, and its magnetic action will draw down the 
iron core, and therefore pull the carbons apart and strike the arc. The moment 
the carbons separate, there will be a difference of potential between them, and 
the shunt coil will then come into action, and will act on the core so as to 
draw the carbons together. Hence the two solenoids act in opposition to each 
other, one in-creasing and the other diminishing the length of the arc, and 
maintaining the carbons in the proper position. In the lamp of this type the 
upper carbon is in reality attached to a rod having a side-rack gearing, with a 
train of wheels governed by a pendulum. The action of the series coil on the 
mechanism is to first lock or stop the train, and then lift it as a whole 
slightly. This strikes the arc. When the arc is too long, the series coil lowers 
the gear and finally releases the upper carbon, so that it can run down by its 
own weight. The principle of a shunt and series coil operating on an iron core 
in opposition is the basis of the mechanism of a number of arc lamps. Thus the 
lamp invented by F. Krizik and L. Piette, called from its place of origin the 
Pilsen lamp, comprises an iron core made in the shape of a double cone or 
spindle (fig. 13), which is so arranged in a brass tube that it can move into or 
out of a shunt and series coil, wound the one with fine and the other with thick 
insulated wire, and hence regulate the position of the carbon attached to it. 
The movement of this core is made to feed the carbons directly without the 
intervention of any clock-work, as in the case of the Hefner-Alteneck lamp. In 
the clutch-lamp mechanism the lower carbon is fixed, and the upper carbon rests 
upon it by its own weight and that of its holder. The latter consists of a long 
rod passing through guides, and is embraced somewhere by a ring capable of being 
tilted or lifted by a finger attached to the armature of an electromagnet the 
coils of which are in series with the arc. When the current passes through the 
magnet it attracts the armature, and by tilting the ring lifts the upper carbon-
holder and hence strikes the arc. If the current diminishes in value, the upper 
carbon drops a little by its own weight, and the feed of the lamp is thus 
effected by a series of small lifts and drops of the upper carbon (fig. 14). 
Another element sometimes employed in arc-lamp mechanism is the brake-wheel 
regulator. This is a feature of one form of the Brockie and of the Crompton-
Pochin lamps. In these the movement of the carbons is effected by a cord or 
chain which passes over a wheel, or by a rack geared with the brake wheel. When 
no current is passing through the lamp, the wheel is free to move, and the 
carbons fall together; but when the current is switched on, the chain or cord 
passing over the brake wheel, or the brake wheel itself is gripped 665 in some 
way, and at the same time the brake wheel is lifted so that the arc is struck.

Although countless forms of self-regulating device have been invented for arc 
lamps, nothing has survived the test of time so well as the typical mechanisms 
which work with carbon rods in one line, one or both rods being moved by a 
controlling apparatus as required. The early forms of semi-incandescent arc 
lamp, such as those of R. Werdermann and others, have dropped out of existence. 
These were not really true arc lamps, the light being produced by the 
incandescence of the extremity of a thin carbon rod pressed against a larger rod 
or block. The once famous Jablochkoff candle, invented in 1876, consisted of two 
carbon rods about 4 mm. in diameter, placed parallel to each other and separated 
by a partition of kaolin, steatite or other refractory non-conductor. 
Alternating currents were employed, and the candle was set in operation by a 
match or starter of high-resistance carbon paste which connected the tips of the 
rods. When this burned off, a true arc was formed between the parallel carbons, 
the separator volatilizing as the carbons burned away. Although much ingenuity 
was expended on this system of lighting between 1877 and 1881, it no longer 
exists. One cause of its disappearance was its relative inefficiency in light-
giving power compared with other forms of carbon arc taking the same amount of 
power, and a second equally important reason was the waste in carbons. If the 
arc of the electric candle was accidentally blown out, no means of relighting 
existed; hence the great waste in half-burnt candles. H. Wilde, J. C. Jamin, J. 
Rapieff and others endeavored to provide a remedy, but without success.

It is impossible to give here detailed descriptions of a fraction of the arc-
lamp mechanisms devised, and it must suffice to indicate the broad distinctions 
between various types. (I) Arc lamps may be either continuous-current or 
alternating-current lamps. For outdoor public illumination the former are 
greatly preferable, as owing to the form of the illuminating power-curve they 
send the light down on the road surface, provided the upper carbon is the 
positive one. For indoor, public room or factory lighting, inverted arc lamps 
are sometimes employed. In this case the positive carbon is the lower one, and 
the lamp is carried in an inverted metallic reflector shield, so that the light 
is chiefly thrown up on the ceiling, whence it is diffused all round. The 
alternating-current arc is not only less efficient in mean spherical candle-
power per watt of electric power absorbed, but its distribution of light is 
disadvantageous for street purposes. Hence when arc lamps have to be worked off 
an alternating-current circuit for public lighting it is now usual to make use 
of a rectifier, which rectifies the alternating current into a unidirectional 
though pulsating current. (2.) Arc lamps may be also classified, as above 
described, into open or en-closed arcs. The enclosed arc can be made to burn for 
200 hours with one pair of carbons, whereas open-arc lamps are usually only able 
to work, 8, 16 or 32 hours without recarboning, even when fitted with double 
carbons. (3) Arc lamps are further divided into focusing and non focusing lamps. 
In the former the lower carbon is made to move up as the upper carbon moves 
down, and the arc is therefore maintained at the same level. This is advisable 
for arcs included in a globe, and absolutely necessary in the case of lighthouse 
lamps and lamps for optical purposes. (4) Another subdivision is into hand-
regulated and self-regulating lamps. In the hand-regulated arcs the carbons are 
moved by a screw attachment as required, as in some forms of search-light lamp 
and lamps for optical lanterns. The carbons in large search-light lamps are 
usually placed horizon-tally. The self-regulating lamps may be classified into 
groups depending upon the nature of the regulating appliances. In some cases the 
regulation is controlled only by a series coil, and in others only by a shunt 
coil. Examples of the former are the original Gulcher and Brush clutch lamp, and 
some modern enclosed arc lamps; and of the latter, the Siemens “band“ lamp, and 
the Jackson-Mensing lamp. In series coil lamps the variation of the current in 
the coil throws into or out of action the carbon-moving mechanism; in shunt coil 
lamps the variation in voltage between the carbons is caused to effect the same 
changes. Other types of lamp involve the use both of shunt and series coils 
acting against each other. 

A further classification of the self-regulating lamps may be found in the nature 
of the carbon-moving mechanism. This may be some modification of the Brush ring 
clutch, hence called clutch lamps; or some variety of brake wheel, as employed 
in Brockie and Crompton lamps; or else some form of electric motor is thrown 
into or out of action and effects the necessary changes. In many cases the arc-
lamp mechanism is provided with a dash-pot, or contrivance in which a piston 
moving nearly air-tight in a cylinder prevents sudden jerks in the motion of the 
mechanism, and thus does away with the “hunting" or rapid up-and-down movements 
to which some varieties of clutch mechanism are liable. One very efficient form 
is illustrated in the Thomson lamp and Brush-Vienna lamp. In this mechanism a 
shunt and series coil are placed side by side, and have iron cores suspended to 
the ends of a rocking arm held partly within them. Hence, according as the 
magnetic action of the shunt or series coil prevails, the rocking arm is tilled 
back-wards or forwards. When the series coil is not in action the motion is 
free, and the upper carbon-holder slides down, or the lower one slides up, and 
starts the arc. The series coil comes into action to withdraw the carbons, and 
at the same time locks the mechanism. The shunt coil then operates against the 
series coil, and between them the carbon is fed forwards as required. The 
control to be obtained is such that the arc shall never become so long as to 
flicker and become extinguished, when the carbons would come together again with 
a rush, but the feed should be smooth and steady, the position of the carbons 
responding quickly to each change in the current.

The introduction of enclosed arc lamps was a great improvement, in consequence 
of the economy effected in the consumption of carbon and in the cost of labor 
for trimming. A well-known and widely used form of enclosed arc lamp is the 
Jandus lamp, which in large current form can be made to burn for two hundred 
hours without re-carboning, and in small or midget form to burn for forty hours, 
taking a current of two amperes at l00 volts. Such lamps in many cases 
conveniently replace large sizes of incandescent lamps, especially for shop 
lighting, as they give a whiter light. Great improvements have also been made in 
inclined carbon arc lamps. One reason for the relatively low efficiency of the 
usual vertical rod arrangement is that the crater can only radiate laterally, 
since owing to the position of the negative carbon no crater light is thrown 
directly downwards. If, however, the carbons are placed in a downwards slanting 
position at a small angle like the letter V and the arc formed at the bottom 
tips, then the crater can emit downwards all the light it produces. It is found, 
however, that the arc is unsteady unless a suitable magnetic field is employed 
to keep the arc in position at the carbon tips. This method has been adopted in 
the Carbon arc, which, by the employment of inclined carbons, and a suitable 
electromagnet to keep the true arc steady at the ends of the carbons, has 
achieved considerable success. One feature of the Carbon arc is the use of a 
relatively high voltage between the carbons, their potential difference being as 
much as 85 volts.

Arc lamps may be arranged either (i.) in series, (ii.) in parallel or (iii.) in 
series parallel. In the first case a number, say 20, may be traversed by the 
same current, in that case a magnetic cut-out, so that if the carbons stick 
together or remain apart the current to the other lamps is not interrupted, the 
function of such a cut-out being to close the main circuit immediately any one 
lamp ceases to pass current. Arc lamps worked in series are generally supplied 
with a current from a constant current dynamo, which maintains an invariable 
current of, say 10 amperes, independently of the number of lamps on the external 
circuit. If the lamps, however, are worked in series off a constant potential 
circuit, such as one supplying at the same time incandescent lamps, provision 
must be made by which a resistance coil can be substituted for any one lamp 
removed or short-circuited. When lamps are worked in parallel, each lamp is 
independent, but it is then necessary to add a resistance in series with the 
lamp. By special devices three lamps can be worked in series of 100 volt 
circuits. Alternating-current arc lamps can be worked off a high-tension circuit 
in parallel by providing each lamp with a small transformer. In some cases the 
alternating high-tension current is rectified and supplied as a unidirectional 
current to lamps in series. If single alternating-current lamps have to be 
worked off a 100 volt alternating-circuit, each lamp must have in series with it 
a choking coil or economy coil, to reduce the circuit pressure to that required 
for one lamp. Alternating-current lamps take a larger effective current, and 
work with a less effective or virtual carbon P.D., than continuous current arcs 
of the same wattage.

The cost of working public arc lamps is made up of several items. There is first 
the cost of supplying the necessary electric cost. energy, then the cost of 
carbons and the labor of recarboning, and, lastly, an item due to depreciation 
and repairs of the lamps. An ordinary type of open Io ampere arc lamp, burning 
carbons 15 and 9 mm. in diameter for the positive and negative, and working 
every night of the year from dusk to dawn, uses about 600 ft. of carbons per 
annum. If the positive carbon is 18 mm. and the negative 12 mm., the consumption 
of each size of carbon is about 70 ft. per 1000 hours of burning. It may be 
roughly stated that at the present prices of plain open arc-lamp carbons the 
cost is about 15s. per 1000 hours of burning; hence if such a lamp is burnt 
every night from dusk to midnight the annual cost in that respect is about I, 
ros. The annual cost of labor per lamp for trimming is in Great Britain from 2 
to 3; hence, approximately speaking, the cost per annum of maintenance of a 
public arc lamp burning every night from dusk to midnight is about 4 to 5, or 
perhaps 6, per annum, depreciation and repairs included. Since such a 10 ampere 
lamp uses half a Board of Trade unit of electric energy every hour, it will take 
r000 Board of Trade units per annum, burning every night from dusk to midnight; 
and if this energy is supplied, say at r 2d. per unit, the annual cost of energy 
will be about 6, and the upkeep of the lamp, including carbons, labor for 
trimming and repairs, will be about 10 to 11 per annum. The cost for labor and 
carbons is considerably reduced by the employment of the enclosed arc lamp, but 
owing to the absorption of light produced by the inner enclosing globe, and the 
necessity for generally employing a second outer globe, there is a lower 
resultant candle-power per watt expended in the arc. Enclosed arc lamps are made 
to burn without attention for zoo hours, singly on 100 volt circuits, or two in 
series on 200 volt circuits, and in addition to the cost of carbons per hour 
being only about one-twentieth of that of the open arc, they have another 
advantage in the fact that there is a more uniform distribution of light on the 
road surface, because a greater proportion of light is thrown out horizontally.

It has been found by experience that the ordinary type of open arc lamp with 
vertical carbons included in an opalescent globe cannot compete in point of cost 
with modern improvements in gas lighting as a means of street illumination. The 
violet color of the light and the sharp shadows, and particularly the non-
illuminated area just beneath the lamp, are grave disadvantages. The high-
pressure flame arc lamp with inclined chemically treated carbons has, however, 
put a different complexion on matters. Although the treated carbons cost more 
than the plain carbons, yet there is a great increase of emitted light, and a 9-
ampere flame arc lamp supplied with electric energy at 1-d. per unit can be used 
for 1000 hours at an inclusive cost of about 5 to 6, the mean emitted 
illumination being at the rate of 4 c.p. per watt absorbed. In the Carbon arc 
lamp, the carbons are worked at an angle of 15 or 200 to each other and the arc 
is formed at the lower ends. If the potential difference of the carbons is low, 
say only 50-6o volts, the crater forms between the tips of the carbons and is 
therefore more or less hidden. If, however, the voltage is increased to 9o-roo 
then the true flame of the arc is longer and is curved, and the crater forms at 
the extreme tip of the carbons and throws all its light downwards. Hence results 
a far greater mean hemispherical candle power (M.H.S.C.P.), so that whereas a 
so-ampere 6o volt open arc gives at most r200 M.H.S.C.P., a Carbon 10-ampere 85 
volt arc will give 2700 M.H.S.C.P. Better results still can be obtained with 
impregnated carbons. But the flame arcs with impregnated carbons cannot be 
enclosed, so the consumption of carbon is greater, and the carbons themselves 
are more costly, and leave a greater ash on burning; hence more trimming is 
required. They give a more pleasing effect for street lighting, and their golden 
yellow globe of light is more useful than an equally costly plain arc of the 
open type. This improvement in efficiency is, however, accompanied by some 
disadvantages. The flame arc is very sensitive to currents of air and therefore 
has to be shielded from draughts by putting it under an "economizer" or chamber 
of highly refractory material which surrounds the upper carbon, or both carbon 
tips, if the arc is formed with inclined carbons. (For additional information on 
flame arc lamps see a paper by L. B. Marks and H. E. Clifford, Electrician, 
1906, 57, P. 975.)

-----------------------------  my notes ----------

If this is not available then try 50% ground up charcoal and 50% lamp black 
(soot from chimney or incomplete burning), and 10% clay or pitch or tar or 
molasses. Heat it in middle of a .5” SS tube.  Pack in more from other end (use 
a packing rod) as heat dries and fuses it into a rod that comes out the other 
end.  If done slow enough it may work to from a rod.  If it gets hot enough it 
will then conduct electricity if not hot enough with no air then it won't 
conduct.  This is all from my current understanding from the above. 



 
