Coloring Electric-light Bulbs And Globes.

—Two substances suggest themselves as excellent vehicles of color, and both water soluble—water glass (potassium or sodium silicate) and gelatin. For tinting, water-soluble aniline colors should be tried. The thickness of the solution must be a matter of experimentation. Prior to dipping the globes they should be made as free as possible from all grease, dirt, etc. The gelatin solution should not be so thick that any appreciable layer of it will form on the surface of the glass, and to prevent cracking, some non-drying material should be added to it, say glycerine.

Rose-tint Glass.

—Selenium is now used for coloring glass. Rose-tinted glass is made by adding selenium directly to the ingredients in the melting pot. By mixing first with cadmium sulphide, orange red is produced. This process is stated not to require the reheating of the glass and its immersion in the coloring mixture, as in the ordinary process of making red glass.

Cutting, Drilling, Grinding, And Shaping Glass:

To Cut Glass.
—I.—Glass may be cut without a diamond. Dip a piece of {372} common string in alcohol and squeeze it reasonably dry. Then tie the string tightly around the glass on the line of cutting. Touch a match to the string and let it burn off. The heat of the burning string will weaken the glass in this particular place. While it is hot plunge the glass under water, letting the arm go well under to the elbow, so there will be no vibration when the glass is struck. With the free hand strike the glass outside the line of cutting, giving a quick, sharp stroke with a stick of wood, a long-bladed knife, or the like, and the cut will be as clean and straight as if made by a regular glass cutter.

The same principle may be employed to cut bottles into vases, and to form all sorts of pretty things, such as jewelry boxes, picture panes, trays, small tablets, windows for a doll house, etc.

II.—Scratch the glass around the shape you desire with the corner of a file or graver; then, having bent a piece of wire into the same shape, heat it red hot and lay it upon the scratch and sink the glass into cold water just deep enough for the water to come almost on a level with its upper surface. It will rarely fail to break perfectly true.

To Cut Glass Under Water.
—It is possible to cut a sheet of glass roughly to any desired shape with an ordinary pair of scissors, if the operation be performed under water. Of course, a smooth edge cannot be obtained by such means, but it will be found satisfactory.
Drilling, Shaping, And Filing Glass.
—Take any good piece of steel wire, file to the shape of a drill, and then hold it in a flame till it is at a dull red heat; then quench in metallic mercury. A piece of good steel, thus treated, will bore through glass almost as easily as through soft brass. In use, lubricate with oil of turpentine in which camphor has been dissolved. When the point of the drill has touched the other side put the glass in water, and proceed with the drilling very slowly. If not possible to do this, reverse the work—turn the glass over and drill, very carefully, from the opposite side. By proceeding with care you can easily drill three holes through glass 3/16 inch thick 1/4 of an inch apart. In making the drill be careful not to make the point and the cutting edges too acute. The drill cuts more slowly, but more safely, when the point and cutting edges are at a low angle.
To Make Holes In Thin Glass.
—To produce holes in panes of thin or weak glass, provide the places to be perforated with a ring of moist loam, whose center leaves free a portion of glass exactly the size of the desired hole. Pour molten lead into the ring, and the glass and lead will fall through at once. This process is based upon the rapid heating of the glass.
To Grind Glass.
—For the grinding of glass, iron, or steel laps and fine sand are first used; after that, the sand is replaced by emery. Then the polishing is started with pure lead or pure tin laps, and finished with willow wood laps. The polishing powder is tin putty, but peroxide of iron or dioxide of tin is a good polishing medium.

Pohl asserts that if glass is polished with crocus (Paris red) it appears of a dark or a yellowish-brown tint. He contends that the crocus enters the pores of the glass, and, to prevent this, he uses zinc white with the most satisfactory results.

A Home-made Outfit For Grinding Glass.
—Provide two pieces of cork, one concave and one convex (which may be cut to shape after fitting to the lathe). Take a copper cent or other suitable article and soft-solder a screw to fit the lathe, and then wax it to the cork; get a cheap emery wheel, such as is used on sewing machines. Polish the edge on the zinc collar of the emery wheel (or use a piece of zinc). The other cork should be waxed to a penny and centered. Spectacle lenses may be cut on the same emery wheel if the wheel is attached to the lathe so as to revolve. Another method is to take a common piece of window glass (green glass is the best) and make a grindstone of that, using the flat surface for grinding. Cement it on a large chuck, the glass being from 2 to 2 1/2 inches in diameter.
To Drill Optical Glass.
—A graver sharpened to a long point is twisted between the fingers, and pressed against the glass, the point being moistened from time to time with turpentine. When the hole is finished half way, the drilling should be commenced from the other side. The starting should be begun with care, as otherwise the graver is likely to slide out and scratch the lens. It is advisable to mark the point of drilling with a diamond, and not to apply too great a pressure when twisting the graver.
Lubricants For Glass Drilling.
—I.—Put garlic, chopped in small pieces, into spirit of turpentine and agitate the {373} mixture from time to time. Filter at the end of a fortnight, and when you desire to pierce the glass dip your bit or drill into this liquid, taking care to moisten it constantly to prevent the drill, etc., from becoming heated.

II.—Place a little alum in acetic acid, dip your drill into this and put a drop of it on the spot where the glass is to be pierced.

Gilding Glass.

When it is desired to gild glass for decorative purposes use a solution of gelatin in hot water, to which an equal quantity of alcohol has been added. The glass to be gilded is covered with this solution and the gold leaf put on while wet. A sheet of soft cotton must be pressed and smoothed over the leaf until the gelatin below is evenly distributed. This prevents spots in gilding. Careful apportionment of the gelatin is necessary. If too much be used, the gold may become spotted; if too little, the binding may be too weak to allow the gold to be polished. The glass should be cleaned thoroughly before gilding. After the gold leaf is put on the whole is allowed to dry for 10 or 20 minutes, when the luster of the gold can be raised by a cautious rubbing with cotton. Then another layer of gelatin is spread on with one stroke of a soft brush, and, if especially good work be required, a second layer of gold is put on and covered as before. In this case, however, the gelatin is used hot. After the gilding has become perfectly dry the letters or ornamentation are drawn and the surplus gold around the edges is taken off. The gilding does not become thoroughly fixed until after several months, and until then rough handling, washing, etc., should be avoided.

The best backing for glass gilding is asphaltum, with a little lampblack, this to be mixed up with elastic varnish; outside finishing varnish is the best, as the addition of this material gives durability.

Glass Manufacturing:

See also Ceramics.

The blue tint of the common poison bottle is got by the addition of black oxide of cobalt to the molten glass; the green tint of the actinic glass bottle is obtained in the same way by the addition of potassium bichromate, which is reduced to the basylous condition, and the amber tint is produced by the addition of impure manganese dioxide, a superior tint being produced by suphur in one form or another. The formulas for various kinds of bottle glass, which indicate the general composition of almost all glasses, are:

White Glass for Ordinary Molded Bottles.—

Sand 64 parts by weight
Lime  6 parts by weight
Carbonate of sodium 23 parts by weight
Nitrate of sodium  5 parts by weight

White Flint Glass Containing Lead.—

Sand 63 parts by weight
Lime  5 parts by weight
Carbonate of sodium 21 parts by weight
Nitrate of sodium  3 parts by weight
Red lead  8 parts by weight

Ordinary Green Glass for Dispensing Bottles.—

Sand 63 parts by weight
Carbonate of sodium 26 parts by weight
Lime 11 parts by weight

A mixture for producing a good green flint glass is much the same as that for the ordinary white flint glass, except that the lime, instead of being the purest, is ordinary slaked lime, and the sodium nitrate is omitted. Sand, lime, and sodium carbonate are the ordinary bases of glass, while the sodium nitrate is the decolorizing agent.

Glass Refractory to Heat.—Fine sand, 70 parts; potash, 30 parts; kaolin, 25 parts.

Transparent Ground Glass.—Take hold of the glass by one corner with an ordinary pair of fire tongs. Hold it in front of a clear fire, and heat to about 98° F., or just hot enough to be held comfortably in the hand. Then hold the glass horizontally, ground side uppermost, and pour in the center a little photographer’s dry-plate negative varnish. Tilt the glass so that the varnish spreads over it evenly, then drain back the surplus varnish into the bottle from one corner of the glass. Hold the glass in front of the fire again for a few minutes and the varnish will crystallize on its surface, making it transparent. The glass should not be made too hot before the varnish is put on, or the varnish will not run evenly. This method answers very well for self-made magic-lantern slides. Ground glass may be made temporarily transparent by wiping with a sponge dipped in paraffine or glycerine.

Water-tight Glass:

Water-tight Glass Roofs.
—Glass roofs, the skeletons of which are constructed {374} of iron, are extremely difficult to keep water-tight, as the iron expands and contracts with atmospheric changes. To meet this evil, it is necessary to use an elastic putty, which follows the variations of the iron. A good formula is: Two parts rosin and one part tallow, melted together and stirred together thoroughly with a little minium. This putty is applied hot upon strips of linen or cotton cloth, on top and below, and these are pasted while the putty is still warm, with one edge on the iron ribs and the other, about one-fourth inch broad, over the glass.
Tightening Agent For Acid Receptacles.
—Cracked vessels of glass or porcelain, for use in keeping acids, can be made tight by applying a cement prepared in the following manner: Take finely sifted sand, some asbestos with short fiber, a little magnesia and add enough concentrated water glass to obtain a readily kneadable mass. The acid renders the putty firm and waterproof.

Pencils For Marking Glass:

See also Etching and Frosted Glass.

Crayons for Writing on Glass.—I.—The following is a good formula:

Spermaceti 4 parts
Tallow 3 parts
Wax 2 parts
Red lead 6 parts
Potassium carbonate 1 part

Melt the spermaceti, tallow, and wax together over a slow fire, and when melted stir in, a little at a time, the potassium carbonate and red lead, previously well mixed. Continue the heat for 20 or 30 minutes, stirring constantly. Withdraw from the source of heat, and let cool down somewhat, under constant stirring, at the temperature of about 180° F.; before the mixture commences to set, pour off into molds and let cool. The latter may be made of bits of glass tubing of convenient diameter and length. After the mixture cools, drive the crayons out by means of a rod that closely fits the diameter of the tubes.

II.—Take sulphate of copper, 1 part, and whiting, 1 part. Reduce these to a fine powder and mix with water; next roll this paste into the shape of crayons and let dry. When it is desired to write on the glass use one of these crayons and wipe the traced designs. To make them reappear breathe on the glass.

III.—Melt together, spermaceti, 3 parts; talc, 3 parts, and wax, 2 parts. When melted stir in 6 parts of minium and 1 part of caustic potash. Continue heating for 30 minutes, then cast in suitable molds. When formed and ready to be put away dust them with talc powder, or roll each pencil in paraffine powder.

Prevention Of Fogging, Dimming, And Clouding.

I.—Place a few flat glass or porcelain dishes with calcium chloride in each window. This substance eagerly absorbs all moisture from the air. The contents of the dishes have to be renewed every 2 or 3 days, and the moist calcium chloride rigorously dried, whereupon it may be used over again.

II.—Apply to the inside face of the glass a thin layer of glycerine, which does not permit the vapor to deposit in fine drops and thus obstruct the light. Double glass may also be used. In this way the heat of the inside is not in direct contact with the cold outside.

III.—By means of the finger slightly moistened, apply a film of soap of any brand or kind to the mirror; then rub this off with a clean, dry cloth; the mirror will be as bright and clear as ever; breathing on it will not affect its clearness.

IV.—Window glass becomes dull during storage by reason of the presence of much alkali. This can be avoided by taking sand, 160 parts; calcined sodium sulphate, 75; powdered marble, 50; and coke, 4 to 5 parts. About 3 parts of the sodium sulphate may be replaced by an equal quantity of potash.

Frosted Glass.

I.—A frosted appearance may be given to glass by covering it with a mixture of

Magnesium sulphate  6 ounces
Dextrin  2 ounces
Water 20 ounces

When this solution dries, the magnesium sulphate crystallizes in fine needles.

II.—Another formula directs a strong solution of sodium or magnesium sulphate, applied warm, and afterwards coated with a thin solution of acacia.

III.—A more permanent “frost” may be put on the glass by painting with white lead and oil, either smooth or in stipple effect. The use of lead acetate with oil gives a more pleasing effect, perhaps, than the plain white lead.

IV.—If still greater permanency is desired, the glass may be ground by rubbing with some gritty substance. {375}

V.—For a temporary frosting, dip a piece of flat marble into glass cutter’s sharp sand, moistened with water; rub over the glass, dipping frequently in sand and water. If the frosting is required very fine, finish off with emery and water. Mix together a strong, hot solution of Epsom salt and a clear solution of gum arabic; apply warm. Or use a strong solution of sodium sulphate, warm, and when cool, wash with gum water. Or daub the glass with a lump of glazier’s putty, carefully and uniformly, until the surface is equally covered. This is an excellent imitation of ground glass, and is not disturbed by rain or damp.

VI.—This imitates ground glass:

Sandarac  2 1/2 ounces
Mastic    1/2 ounce
Ether 24 ounces
Benzine 16 to 18 ounces

VII.—Take white lead ground in a mixture of 3/4 varnish and 1/4 oil of turpentine, to which burnt white vitriol and white sugar of lead are added for drier. The paint must be prepared exceedingly thin and applied to the glass evenly, using a broad brush. If the windows require a new coat, the old one is first removed by the use of a strong lye, or else apply a mixture of hydrochloric acid, 2 parts; vitriol, 2 parts; copper sulphate, 1 part; and gum arabic 1 part, by means of a brush. The production of this imitation frosting entails little expense and is of special advantage when a temporary use of the glass is desired.

VIII.—A little Epsom salt (sulphate of magnesia) stirred in beer with a small dose of dextrin and applied on the panes by means of a sponge or a brush permits of obtaining mat panes.

Hoarfrost Glass.
—The feathery foams traced by frost on the inside of the windows in cold weather may be imitated as follows:

The surface is first ground either by sand-blast or the ordinary method, and is then covered with a sort of varnish. On being dried either in the sun or by artificial heat, the varnish contracts strongly, taking with it the particles of glass to which it adheres; and as the contraction takes places along definite lines, the pattern given by the removal of the particles of glass resembles very closely the branching crystals of frostwork. A single coat gives a small, delicate effect, while a thick film, formed by putting on 2, 3 or more coats, contracts so strongly as to produce a large and bold design. By using colored glass, a pattern in half-tint may be made on the colored ground, and after decorating white glass, the back may be silvered or gilded.

Engraving, Matting, And Frosting.
—Cover the glass with a layer of wax or of varnish on which the designs are traced with a graver or pen-point; next, hydrofluoric acid is poured on the tracings. This acid is very dangerous to handle, while the following process, though furnishing the same results, does not present this drawback: Take powdered fluoride of lime, 1 part, and sulphuric acid, 2 parts. Make a homogeneous paste, which is spread on the parts reserved for the engraving or frosting. At the end of 3 or 4 hours wash with water to remove the acid, next with alcohol to take off the varnish, or with essence of turpentine if wax has been employed for stopping off.
To Render Window Panes Opaque.
—I.—Panes may be rendered mat and non-transparent by painting them on one side with a liquid prepared by grinding whiting with potash water-glass solution. After one or two applications, the panes are perfectly opaque, while admitting the light.

II.—Paint the panes with a solution of

Dextrin   200 parts by weight
Zinc vitriol   800 parts by weight
Bitter salt   300 parts by weight
In water 2,000 parts by weight

III.—For deadening panes already set in frames the following is suitable: Dissolve 1 part of wax in 10 parts of oil of turpentine, adding 1 part of varnish and 1 part of siccative. With this mixture coat the panes on the outside and dab, while still wet, with a pad of cotton wadding. If desired small quantities of Paris blue, madder lake, etc., may be added to the wax solution.

IV.—For deadening window panes in factories and workshops: To beeswax dissolved in oil of turpentine, add some dryer and varnish to obtain a quicker drying and hardening. After the window pane has been coated with this mixture on the outside, it is dabbed uniformly with a pad of wadding. The wax may be tinted with glazing colors.

Frosted Mirrors.
—I.—Cover with a solution of Epsom salts in stale beer; apply with a sponge to the mirror, first wiping it clean and dry. On drying, the Epsom salt crystallizes, giving very handsome frosted effects, but the solution must not be applied on humid days {376} when the glass is liable to be damp, for in that case the effect will be a blurred one. When it is desirable to remove the coating, lukewarm water will serve the purpose without damage to the luster of the mirror.

II.—The following mixture, when applied to a mirror and left to dry, will form in many shapes, all radiating from a focus, this focus forming anywhere on the glass, and when all dry tends to form a most pleasing object to the eye.

Sour ale 4 ounces
Magnesium sulphate 1 ounce

Put on the mirror with a small, clean sponge and let dry. It is now ready for the artist, and he may choose his own colors and subject.

Crystalline Coatings Or Frostwork On Glass Or Paper.
—Dissolve a small quantity of dextrin (gum arabic and tragacanth are not so suitable) in aqueous salt solution as concentrated as possible, for instance, in sulphate of magnesia (bitter salt), sulphate of zinc or any other readily crystallizing salt; filter the solution through white blotting paper and coat glass panes uniformly thin with the clear filtrate, using a fine, broad badger brush; leave them lying at an ordinary medium temperature about one-quarter hour in a horizontal position.

As the water slowly evaporates during this short time, handsome crystalline patterns, closely resembling frostwork, will develop gradually on the glass panes, which adhere so firmly to the glass or the paper (if well-sized glazed paper had been used) that they will not rub off easily. They can be permanently fixed by a subsequent coat of alcoholic shellac solution.

Especially handsome effects are produced with colored glass panes thus treated, and in the case of reflected light by colored paper.

For testing crystals as regards their optical behavior, among others their behavior to polarized light, it is sufficient to pour a solution of collodion wool (soluble peroxide lime for the preparation of collodion) over the surface of glass with the crystalline designs, and to pull off the dry collodion film carefully. If this is done cautiously it is not difficult to lift the whole crystalline group from the glass plate and to incorporate it with the glass-like, thin collodion film.

Removing Window Frost.

Here are fourteen methods of preventing frost on windows, arranged in the order of their efficacy: 1, Flame of an alcohol lamp; 2, sulphuric acid; 3, aqua ammonia; 4, glycerine; 5, aqua regia; 6, hydrochloric acid; 7, benzine; 8, hydriodic acid; 9, boric acid; 10, alcohol; 11, nitric acid; 12, cobalt nitrate; 13, infusion of nutgalls; 14, tincture of ferrous sulphate. By the use of an alcohol lamp (which, of course, has to be handled with great care) the results are immediate, and the effect more nearly permanent than by any other methods. The sulphuric acid application is made with a cotton cloth swab, care being taken not to allow any dripping, and so with all other acids. The effect of the aqua ammonia is almost instantaneous, but the window is frosted again in a short time. With the glycerine there are very good results—but slight stains on the window which may be easily removed.

The instructions for glycerine are: Dissolve 2 ounces of glycerine in 1 quart of 62 per cent alcohol containing, to improve the odor, some oil of amber. When the mixture clarifies it is rubbed over the inner surface of the glass. This, it is claimed, not only prevents the formation of frost, but also prevents sweating.

To Prevent Dimming Of Eyeglasses, Etc.
—Mix olein-potash soap with about 3 per cent of glycerine and a little oil turpentine. Similar mixtures have also been recommended for polishing physicians’ reflectors, show-windows, etc., to prevent dimming.

Writing On Glass:

See also Etching and Inks.

Composition For Writing On Glass.
—To obtain mat designs on glass, take sodium fluoride, 35 parts; potassium sulphate, 7 parts; zinc chloride, 15 parts; hydrochloric acid, 65 parts; distilled water, 1,000 parts. Dissolve the sodium fluoride and the potassium sulphate in half the water; dissolve the zinc chloride in the remaining water and add the hydrochloric acid. Preserve these two solutions separately. For use, mix a little of each solution and write on the glass with a pen or brush.
Ink For Writing On Glass.—
Shellac  20 parts
Alcohol 150 parts
Borax  35 parts
Water 250 parts
Water-soluble dye sufficient to color.

Dissolve the shellac in the alcohol, the borax in the water, and pour the shellac {377} solution slowly into that of the borax. Then add the coloring matter previously dissolved in a little water.

GLASS AND GLASSWARE CEMENT: See Adhesives and Amalgams.

GLASS CLEANERS: See Cleaning Preparations and Methods.

GLASS, COPPERING, GILDING, AND PLATING: See Plating.

GLASS ETCHING: See Etching.

GLASS, HOW TO AFFIX SIGN-LETTERS ON: See Adhesives under Sign-Letter Cements.

GLASS, FASTENING METALS ON: See Adhesives.

GLASS LETTERING: See Lettering.

GLASS LUBRICANTS: See Lubricants.

GLASS, PERCENTAGE OF LIGHT ABSORBED BY: See Light.

GLASS POLISHES: See Polishes.

GLASS, SILVERING OF: See Mirrors.

GLASS SOLDERS: See Solders.

GLASS, SOLUBLE, AS A CEMENT: See Adhesives.

GLASS, TO AFFIX PAPER ON: See Adhesives, under Water-Glass Cements.

GLASS, TO SILVER: See Silver.

GLAZES

(See also Ceramics, Enamels, Paints, and Varnishes.)

Glazes For Cooking Vessels.

—Melt a frit of red lead, 22.9 parts (by weight); crystallized boracic acid, 31 parts; enamel soda, 42.4 parts; cooking salt, 10 parts; gravel, 12 parts; feldspar, 8 parts. According to the character of the clay, this frit is mixed with varying quantities of sand, feldspar and kaolin, in the following manner:
Frit 84 84 84 84
Red lead  1.5  1.5  1.5  1.5
Gravel  8  6  3 ───
Feldspar ───  2  5  8
Kaolin, burnt  6.5  6.5  6.5  6.5

Glazes which are produced without addition of red lead to the frit, are prepared as follows. Melt a frit of the following composition: Red lead, 22.9 parts (by weight); boracic acid in crystals, 24.8 parts; enamel soda, 37.1 parts; calcined potash, 6.9 parts; cooking salt, 10 parts; chalk, 10 parts; gravel, 12 parts; feldspar, 8 parts.

From the frit the following glazes are prepared:

Frit 86.5 86.5 86.5 86.5
Gravel  7  4.5  3 ───
Feldspar ───  2.5  4  7
Kaolin, burnt  6.5  6.5  6.5  6.5

Glazing On Size Colors.

—The essential condition for this work is a well-sized foundation. For the glazing paint, size is likewise used as a binder, but a little dissolved soap is added, of about the strength employed for coating ceilings. Good veining can be done with this, and a better effect can be produced in executing pieces which are to appear in relief, such as car-touches, masks, knobs, etc., than with the ordinary means. A skillful grainer may also impart to the work the pleasant luster of natural wood. The same glazing method is applicable to colored paintings. If the glazing colors are prepared with wax, dissolved in French turpentine, one may likewise glaze with them on a size-paint ground. Glazing tube-oil colors thinned with turpentine and siccative, are also useful for this purpose. For the shadows, asphalt and Van Dyke brown are recommended, while the contour may be painted with size-paint.

Coating Metallic Surfaces With Glass.

—Metallic surfaces may be coated with glass by melting together 125 parts (by weight) of flint-glass fragments, 20 parts of sodium carbonate, and 12 parts of boracic acid. The molten mass is next poured on a hard and cold surface, stone or metal. After it has cooled, it is powdered. Make a mixture of 50° Bé. of this powder and sodium silicate (water glass). The metal to be glazed is coated with this and heated in a muffle or any other oven until the mixture melts and can be evenly distributed. This glass coating adheres firmly to iron and steel.

Glaze For Bricks.

—A glazing color for bricks patented in Germany is a {378} composition of 12 parts (by weight) lead; 4 parts litharge; 3 parts quartzose sand; 4 parts white argillaceous earth; 2 parts kitchen salt; 2 parts finely crushed glass, and 1 part saltpeter. These ingredients are all reduced to a powder and then mixed with a suitable quantity of water. The color prepared in this manner is said to possess great durability, and to impart a fine luster to the bricks.

GLAZES FOR LAUNDRY: See Laundry Preparations.

GLOBES, HOW TO COLOR: See Glass-Coloring.

GLOBES, PERCENTAGE OF LIGHT ABSORBED BY: See Light.

GLOBES, SILVERING OF: See Mirrors.

GLOSS FOR PAPER: See Paper.

GLOVE-CLEANERS: See Cleaning Compounds.

GLOVES, SUBSTITUTE FOR RUBBER: See Antiseptics.

GLOVES, TESTING: See Rubber.

GLUCOSE IN JELLY: See Foods.

GLUE

(Formulas for Glues and methods of manufacturing Glue will be found under Adhesives.)

Rendering Glue Insoluble In Water.

—Stuebling finds that the usual mixture of bichromate and glue when used in the ordinary way does not possess the waterproof properties with which it is generally credited. If mixed in the daylight, it sets hard before it can be applied to the surfaces to be glued, and if mixed and applied in the dark room it remains just as soluble as ordinary glue, the light being unable to penetrate the interior of the joints. Neither is a mixture of linseed oil and glue of any use for this purpose. Happening to upset a strong solution of alum—prepared for wood staining—into an adjacent glue pot, he stirred up the two together out of curiosity and left them. Wishing to use the glue a few days later, he tried to thin it down with water, but unsuccessfully, the glue having set to a waterproof mass. Fresh glue was then mixed with alum solution and used to join two pieces of wood, these resisting the action of the water completely.

To Bleach Glue.

—Dissolve the glue in water, by heat, and while hot, add a mixture in equal parts of oxalic acid and zinc oxide, to an amount equal to about 1 per cent of the glue. After the color has been removed, strain through muslin.

Method Of Purifying Glue.

—The glue is soaked in cold water and dissolved in a hot 25 per cent solution of magnesium sulphate. The hot solution is filtered, and to the filtrate is added a 25 per cent solution of magnesium sulphate containing 0.5 per cent of hydrochloric acid (or, if necessary, sulphuric acid). A white flocculent precipitate is obtained which is difficult to filter. The remainder of the glue in the saline solution is extracted by treatment with magnesium sulphate.

The viscous matter is washed, then dissolved in hot water, and allowed to cool, a quantity of weak alcohol acidulated by 1 per cent of hydrochloric acid being added just before the mass solidifies. From 2 to 3 parts, by volume, of strong alcohol (methyl or ethyl) are then added and the solution filtered, charcoal being used if necessary. The glue is finally precipitated from this solution by neutralizing with ammonia and washing with alcohol or water.

To Distinguish Glue And Other Adhesive Agents.

—The product to be examined is heated with hydrofluoric acid (50 per cent). If bone glue is present in any reasonable quantity, an intense odor of butyric acid arises at once, similar to that of Limburger cheese. But if dextrin or gum arabic is present, only an odor of dextrine or fluorhydric acid will be perceptible. Conduct the reaction with small quantities; otherwise the smell will be so strong that it is hard to remove from the room.

GLUE CLARIFIER: See Gelatin.

GLYCERINE

Recovering Glycerine From Soap Boiler’s Lye.

—I.—Glycerine is obtained as a by-product in making soap. For many years the lyes were thrown away as waste, but now considerable quantities of glycerine are recovered, which are much used in making explosive compounds.

When a metallic salt or one of the alkalies, as caustic soda, is added to tallow, a stearite of the metal (common soap is stearite of sodium) is formed, whereby the glycerine is eliminated. {379} This valuable by-product is contained in the waste lye, and has formed the subject of several patents.

Draw the lye off from the soap-pans; this contains a large quantity of water, some salt and soap and a small quantity of glycerine, and the great trouble is to concentrate the lye so that the large quantity of water is eliminated, sometimes 10 to 12 days being occupied in doing this. The soap and salt are easily removed.

To remove the soap, run the lye into a series of tanks alternating in size step-like, so that as the first, which should be the largest, becomes full, the liquor will flow into the second, from that into the third, and so on; by this arrangement the rosinous and albuminous matters will settle, and the soap still contained in the lyes will float on the surface, from which it is removed by skimming.

After thus freeing the lye of the solid impurities, convey the purified lye to the glycerine recovering department (wooden troughs or pipes may be used to do this), and after concentrating by heating it in a steam-jacketed boiler, and allowing it to cool somewhat, ladle out the solid salt that separates, and afterwards concentrate the lye by allowing it to flow into a tank, but before doing so let the fluid come in contact with a hot blast of air or superheated steam, whereby the crude discolored glycerine is obtained. This is further purified by heating with animal charcoal to decolorize it, then distilling several times in copper stills with superheated steam. The chief points to attend to are: (1) The neutralizing and concentrating the lye as much as possible and then separating the salts and solid matters; (2) concentrating the purified lye, and mixing this fluid with oleic acid, oil, tallow, or lard, and heating the mixture to 338° F., in a still, by steam, and gradually raise the heat to 372° F.; (3) stirring the liquor while being heated, and allowing the aqueous vapor to escape, and when thus concentrated, saponifying the liquid with lime to eliminate the glycerine; water is at the same time expelled, but this is removed from the glycerine by evaporating the mixture.

II.—In W. E. Garrigues’s patent for the recovering of glycerine from spent soap lyes, the liquid is neutralized with a mineral acid, and after separation of the insoluble fatty acids it is concentrated and then freed from mineral salts and volatile fatty acids, and the concentrated glycerine solution treated with an alkaline substance and distilled. Thus the soap lye may be neutralized with sulphuric acid, and aluminum sulphate added to precipitate the insoluble fatty acids. The filtrate from these is concentrated and the separated mineral salts removed, after which barium chloride is added and then sufficient sulphuric acid to liberate the volatile fatty acids combined with the alkali. These acids are partially enveloped in the barium sulphate, with which they can be separated from the liquid by filtration, while the remaining portion can be expelled by evaporating the liquid in a vacuum evaporator. Finally, the solution is treated with sodium carbonate, and the glycerine distilled.

Glycerine Lotion.—

Glycerine 4 ounces
Essence bouquet   1/4 ounce
Water 4 ounces
Cochineal coloring, a sufficient quantity.

(See also Cosmetics for Glycerine Lotions.)

GLYCERINE APPLICATIONS: See Cosmetics.

GLYCERINE AS A DETERGENT: See Cleaning Preparations and Methods.

GLYCERINE PROCESS: See Photography.

GLYCERINE SOAP: See Soap.

GLYCERINE DEVELOPER: See Photography.

GOLD

(See also Jewelers’ Formulas.)

Gold Printing On Oilcloth And Imitation Leather.

—Oilcloth can very easily be gilt if the right degree of heat is observed. After the engraving has been put in the press, the latter is heated slightly, so that it is still possible to lay the palm of the hand on the heated plate without any unpleasant sensation. Go over the oilcloth with a rag in which a drop of olive oil has been rubbed up, which gives a greasy film. No priming with white of egg or any other priming agent should be done, since the gold leaf would stick. Avoid sprinkling on gilding powder. The gold leaf is applied directly on the oilcloth; then place in the lukewarm press, squeezing it down with {380} a quick jerky motion and opening it at once. If the warm plate remains too long on the oilcloth, the gold leaf will stick. When the impression is done, the gold leaf is not swept off at once, but the oilcloth is first allowed to cool completely for several minutes, since there is a possibility that it has become slightly softened under the influence of the heat, especially at the borders of the pressed figures, and the gold would stick there if swept off immediately. The printing should be sharp and neat and the gold glossy. For bronze printing on oilcloth, a preliminary treatment of printing with varnish ground should be given. The bronze is dusted on this varnish.

Imitation leather is generally treated in the same manner. The tough paper substance is made to imitate leather perfectly as regards color and pressing, especially the various sorts of calf, but the treatment in press gilding differs entirely from that of genuine leather. The stuff does not possess the porous, spongy nature of leather, but on the contrary is very hard, and in the course of manufacture in stained-paper factories is given an almost waterproof coating of color and varnish. Hence the applied ground of white of egg penetrates but slightly into this substance, and a thin layer of white of egg remains on the surface. The consequence is that in gilding the gold leaf is prone to become attached, the ground of albumen being quickly dissolved under the action of the heat and put in a soft sticky state even in places where there is no engraving. In order to avoid this the ground is either printed only lukewarm, or this imitation leather is not primed at all, but the gold is applied immediately upon going over the surface with the oily rag. Print with a rather hot press, with about the same amount of heat as is employed for printing shagreen and title paper. A quick jerky printing, avoiding a long pressure of the plate, is necessary.

Liquid Gold.

—Take an evaporating dish, put into it 880 parts, by weight, of pure gold; then 4,400 parts, by weight, of muriatic acid, and 3,520 parts, by weight, nitric acid; place over a gas flame until the gold is dissolved, and then add to it 22 parts, by weight, of pure tin; when the tin is dissolved add 42 parts, by weight, of butter of antimony. Let all remain over the gas until the mixture begins to thicken. Now put into a glass and test with the hydrometer, which should give about 1,800 specific gravity. Pour into a large glass and fill up with water until the hydrometer shows 1090; pour all the solution into a chemical pot and add to it 1,760 parts, by weight, balsam of sulphur, stirring well all the while, and put it over the gas again; in an hour it should give, on testing, 125° F.; gradually increase the heat up to 185° F., when it should be well stirred and then left to cool about 12 hours. Pour the watery fluid into a large vessel and wash the dark-looking mass 5 or 6 times with hot water; save each lot of water as it contains some portion of gold. Remove all moisture from the dark mass by rolling on a slab and warming before the fire occasionally so as to keep it soft. When quite dry add 2 1/4 times its weight of turpentine and put it over a small flame for about 2 hours; then slightly increase the heat for another hour and a half. Allow this to stand about 24 hours, and then take a glazed bowl and spread over the bottom of it 1,760 parts, by weight, of finely powdered bismuth; pour the prepared gold over it in several places. Now take a vessel containing water and place inside the other vessel containing the gold, and heat it so as to cause the water to boil for 3 hours; allow it to remain until settled and pour off the gold from the settlings of the bismuth, and try it; if not quite right continue the last process with bismuth until good; the bismuth causes the gold to adhere.