[HN Gopher] Fluorescence in Olive Oil
       ___________________________________________________________________
        
       Fluorescence in Olive Oil
        
       Author : jjoe
       Score  : 120 points
       Date   : 2023-04-15 10:29 UTC (12 hours ago)
        
 (HTM) web link (aapt.scitation.org)
 (TXT) w3m dump (aapt.scitation.org)
        
       | Mistletoe wrote:
       | https://academic.oup.com/jaoac/article/83/6/1435/5656401#198...
       | 
       | > Fluorescence spectra of some common vegetable oils, including
       | olive oil, olive residue oil, refined olive oil, corn oil,
       | soybean oil, sunflower oil, and cotton oil, were examined in
       | their natural state, with a wavelength of 360 nm used as
       | excitation radiation. All oils studied, except extra virgin olive
       | oil, exhibited a strong fluorescence band at 430-450 nm. Extra
       | virgin olive oil gave a different by interesting fluorescence
       | spectrum, composed of 3 bands: one low intensity doublet at 440
       | and 455 nm, one strong at 525 nm, and one of medium intensity at
       | 681 nm. The band at 681 nm was identified as the chlorophyll
       | band. The band at 525 nm was at least partly derived from vitamin
       | E. The low intensity doublet at 440 and 455 nm correlated with
       | the absorption intensity at 232 and 270 nm of olive oil. The
       | measurements of these fluorescence spectra were quick (about 5
       | min) and easy and could possibly be used for authentification of
       | virgin olive oil.
       | 
       | From a Halloween website, may provide a clue to the red.
       | 
       | > Chlorophyll is green under regular light, but will fluoresce
       | red under a black light. Chlorophyll fluoresces red under UV
       | light.
        
       | ChrisMarshallNY wrote:
       | Colavita EVOO turns fairly bright orange.
       | 
       | I wonder if this could be a way to test for purity. I know that
       | most EVOO is garbage.
        
         | denton-scratch wrote:
         | > I know that most EVOO is garbage.
         | 
         | I don't know about "garbage". What do you mean by "garbage"? Do
         | you mean not from olives? Not extra-virgin? Or just not very
         | nice? Where? Perhaps this is true in the USA? I'm in Europe,
         | and I don't know anything about the US olive oil market.
         | 
         | I do believe that a lot of EVOO isn't what it purports to be;
         | for example, I believe a lot of purportedly Italian EVOO is cut
         | with Spanish oil; but I can't substantiate that belief.
        
           | sbaiddn wrote:
           | A lot of Italian olive oil isnt from olives. There was a huge
           | scandal a few years ago of local producers adulterating olive
           | oil (right around the time the dioxin laced mozzarella
           | happened)
           | 
           | Thats why I buy Californian or Greek olive oil. Not that I
           | trust Greeks more than any other European, but their very
           | good stuff is so good its obviously olive oil.
        
             | robocat wrote:
             | Previous HN discussion on NY Times article about
             | adulteration: https://news.ycombinator.com/item?id=7128495
        
           | wahnfrieden wrote:
           | The biggest issue is people using stale oils from over a year
           | ago instead of fresh harvest. Olive oil loses flavor and goes
           | bad earlier than it goes completely rancid. Most retail is
           | deceptive about harvest date.
        
           | VLM wrote:
           | Its bad enough out there that the general public thinks the
           | smell of hexane is what olive oil is supposed to smell like.
           | Like you open a container of hexane in the chemistry lab and
           | people say it smells like cooking oil. Um... not supposed to,
           | no.
           | 
           | Kind of like how younger people think tomatoes and
           | strawberries are supposed to be flavorless and odorless.
        
             | YeGoblynQueenne wrote:
             | What surprised me was finding out that US people think that
             | EVOO burns easily and turns bitter when fried. I found out
             | when I was watching a youtube video from a foodie
             | influencer, I'll see if I can find it.
             | 
             | Anyway, for me that's incomprehensible. I have stir fried
             | with EVOO all my life and I have never seen it burn. The
             | only exception is when I've accidentally, and stupidly,
             | left the pan with only olive oil in it in full heat and
             | went off to do something else, at which point it starts
             | smoking and smelling bad. I have also never had it turn
             | bitter, no matter what I've done with it. I've burned food
             | cooked in olive oil, and occasionally the food has turned
             | bitter (burned onions and garlic taste bitter for example;
             | eugh) but mostly it just tastes burnt.
             | 
             | I've also used olive oil for deep frying and again it has
             | never burnt on me, although lately I prefer to use cheaper
             | oils, like sunflower oil, also because I find that deep
             | frying with olive oil makes food taste too heavy, as if you
             | cooked it in lard or fat (and that's not what I'm going for
             | when I make chips or falafel, say).
             | 
             | So my conclusion is that people outside the Mediterranean,
             | including in the US, just don't normally cook with good
             | quality EVOO. I can certainly see lower quality olive oils
             | behaving badly at high temperatures.
        
               | mindcrime wrote:
               | _The only exception is when I 've accidentally, and
               | stupidly, left the pan with only olive oil in it in full
               | heat and went off to do something else, at which point it
               | starts smoking and smelling bad._
               | 
               | Getting a little off-topic here, but as a former
               | firefighter, please allow me to plead with everyone
               | reading this to not ever start cooking (on the stove-top
               | anyway) and "go off to do something else." Fires start
               | (and spread) much more rapidly than most people's naive
               | intuitions tell them, and we're also much more vulnerable
               | to getting distracted and forgetting about the cooking,
               | than most of us want to admit.
               | 
               | Note that cooking (particularly including unattended
               | cooking) is generally the leading cause of structure
               | fires, at least in the US in recent history.
               | 
               | https://www.nfpa.org/Public-Education/Fire-causes-and-
               | risks/...                   Cooking was the leading cause
               | of reported home fires and home fire injuries in
               | 2015-2019 and the second leading cause of home fire
               | deaths. Cooking caused 49 percent of reported home fires,
               | 20 percent of reported home fire deaths, and 42 percent
               | of home fire injuries.                   Based on
               | 2014-2018 annual averages:              Two-thirds  of
               | home cooking fires start with the ignition of food or
               | other cooking materials.         Clothing is the item
               | first ignited in less than 1% of these fires, but
               | clothing ignitions caused 8% of the home cooking fire
               | deaths.         Ranges or cooktops account for three-
               | fifths of home cooking fire incidents.         Unattended
               | equipment is a factor in one-third of reported home
               | cooking fires and over half of the associated deaths.
               | Frying dominates the cooking fire problem.
        
               | zokier wrote:
               | Extra virgin olive oil is definitely on the lower end of
               | cooking oil smoke point spectrum, that is not really
               | contentious point. Refined olive oils (e.g. extra light)
               | tend have higher smoke points, same is true afaik for
               | most vegetable oils.
               | 
               | If you have not observed olive oil smoking, then that is
               | more reflective of your cooking habits than the oil
               | itself.
        
               | YeGoblynQueenne wrote:
               | Are you sure about that? Because my cooking habits are
               | not anything strange. As I say above, I stir fry and I've
               | deep fried, and I do everything else that you can do with
               | shortening, with EVOO, and it doesn't burn.
               | 
               | Where does your information about EVOO being "on the
               | lower end of cooking oil smoke point spectrum" come from?
               | 
               | And what kind of EVOO are we talking about? There are
               | different qualities of EVOO with drastically different
               | behaviour, but they're all sold as EVOO.
        
               | zokier wrote:
               | Pretty much any list of oil smoking points confirms it,
               | here is an example https://www.seriouseats.com/cooking-
               | fats-101-whats-a-smoke-p...
               | 
               | Or here is one table from an olive oil producer:
               | https://savantes.org/news-and-articles/cooking-and-using-
               | oli...
               | 
               | If you disagree then the burden of proof is on you.
        
               | YeGoblynQueenne wrote:
               | The two lists you found never say what "Extra virgin
               | olive oil" they list, where it came from, and how they
               | knew it was not adulterated. They don't say where the
               | numbers in their tables originally come from, either
               | (they list secondary sources, like food textbooks and
               | wikipedia) [1].
               | 
               | Surely you can see that if "EVOO" is commonly adulterated
               | with lower-quality olive oils, then the measurements of
               | its smoke point are not going to be representative? >> If
               | you disagree then the burden of proof is on you.
               | 
               | I'm sorry but why is there a "burden of proof" on anyone
               | here? I just remarked that I've never seen olive oil burn
               | while cooking. How exactly could I "prove" that?
               | 
               | I hope you are not trying to invite yourself over for
               | dinner :|
               | 
               | _______________
               | 
               | [1] What's more, the second source seems really confused
               | about the difference between extra-virgin and refined
               | olive oils:
               | 
               |  _You will note that refining oils tends to increase the
               | smoke point as impurities and free fatty acids are
               | removed. Hence refined 'extra light' olive oil has a
               | higher smoke point than extra virgin olive oil. The table
               | shows that high quality extra virgin olive oil has a
               | higher smoke point than refined - due to the presence of
               | anti-oxidants and low free fatty acid levels. Another
               | selling point for high quality extra virgin olive oils._
               | 
               | https://savantes.org/news-and-articles/cooking-and-using-
               | oli...
               | 
               | So which one is it? Is it "refined 'extra light' olive
               | oil [has] a higher smoke point than extra virgin olive
               | oil" or is it "high quality extra virgin olive oil has a
               | higher smoke point than refined"?
        
               | denton-scratch wrote:
               | Thanks for those links; I didn't realize that clarified
               | butter came in with such a high smoke point.
               | 
               | I usually use a mixture of (unclarified) butter and EVOO
               | for frying steaks; tonight I shall try just clarified
               | butter (with flavourings - thyme and garlic). It makes
               | sense; and maybe I'll get a decent pan-sauce this time.
        
               | wahnfrieden wrote:
               | Burning it is easy, and a technique sometimes to add
               | astringency for balance depending on what exactly you're
               | doing. Common mistake is to heat oil on a cold pan though
               | - lots of unnecessary burning of flavor/smoke to reach
               | sometimes necessary high momentary temperatures
        
           | YeGoblynQueenne wrote:
           | There's a good deal of information about this in the
           | wikipedia page on olive oil:
           | 
           | https://en.wikipedia.org/wiki/Olive_oil#Adulteration
           | 
           | Some excerpts from the article (cherry-picked to be relevant
           | to the conversation):
           | 
           | >> There have been allegations, particularly in Italy and
           | Spain, that regulation can be sometimes lax and corrupt.[75]
           | Major shippers are claimed to routinely adulterate olive oil
           | so that only about 40% of olive oil sold as "extra virgin" in
           | Italy actually meets the specification.[76]
           | 
           | >> On 3 January 2016 Bill Whitaker presented a program on CBS
           | News including interviews with Mueller and with Italian
           | authorities.[85][86] It was reported that in the previous
           | month 5,000 tons of adulterated olive oil had been sold in
           | Italy, and that organised crime was heavily involved--the
           | term "Agrimafia" was used. The point was made by Mueller that
           | the profit margin on adulterated olive oil was three times
           | that on the illegal narcotic drug cocaine. He said that over
           | 50% of olive oil sold in Italy was adulterated, as was 75-80%
           | of that sold in the US. Whitaker reported that three samples
           | of "extra virgin olive oil" had been bought in a US
           | supermarket and tested; two of the three samples did not meet
           | the required standard, and one of them--with a top-selling US
           | brand--was exceptionally poor.
           | 
           | >> A Carabinieri investigator interviewed on the program said
           | that "olive oil fraud has gone on for the better part of four
           | millennia" but today, it's particularly "easy for the bad
           | guys to either introduce adulterated olive oils or mix in
           | lower quality olive oils with extra-virgin olive oil".[88]
           | Weeks later, a report by Forbes stated that "it's reliably
           | reported that 80% of the Italian olive oil on the market is
           | fraudulent" and that "a massive olive oil scandal is being
           | uncovered in Southern Italy (Puglia, Umbria and
           | Campania)".[89]
           | 
           | I'm from Greece; you know, the other major oil producing
           | country :P We, too, like the Italians and the Spanish, value
           | olive oil very highly. I don't know of any adulteration
           | scandals for Greek EVOO, but that doesn't mean it doesn't
           | happen. It's easy to believe that a producer whose oil turns
           | out not very good in a particular year, even if it is
           | normally good-quality would feel rather desperate and it's
           | easy to see how some would be tempted to do something about
           | it. For example, a few years ago in Corfu, there was much
           | anger when much of the olive oil produced on the island were
           | found to be unfit for human consumption because of very high
           | levels of pesticides. That year, the communally organised
           | spraying of olive groves from the air was stopped and
           | produces had started spraying their olives on their own.
           | Apparently many just overdid it, presumably following the
           | age-old wisdom that if a little is good, a lot is better.
           | Even without that little mishap, olive oil from Corfu is
           | normally too acidic, because of the way the olives are
           | collected (they are left to fully ripen on the trees and
           | collected when they fall off naturally). That means that even
           | extra virgin olive oil produced in Corfu may not be the best
           | quality. That in turn means it won't be bought at the same
           | price as better quality oils by the large bottling
           | corporations. So it might well end up sold to the Italians
           | and blended with their own oils, of whatever category. In
           | that case, the consumer may buy "Italian" and "extra virgin
           | olive oil" but even if it is really EVOO, it might still be
           | not the best quality; but it will be sold at a high price
           | anyway.
           | 
           | I have to confess I can't be sure I haven't inadvertently
           | bought second-quality, or even adulterated, EVOO at some
           | point in my life. I consume vast quantities of the stuff. I
           | only cook my food with it, basically, rarely anything else. I
           | am pretty sure I could identify non-EVOO with eyes closed. A
           | couple of weeks ago my partner bought some olive oil and when
           | I went to cook with it, it looked... different? Kind of too
           | thin and too clear. I checked the container and it was
           | blended oil that included refined oils. The container was
           | exactly the same as the one of the EVOO we normally buy so my
           | partner mistook it for our standard. But it was obvious it
           | wasn't our standard. There's a clear difference. On the other
           | hand, I'm not sure that the people who adulterate EVOO make
           | it so easy to tell.
        
           | ChrisMarshallNY wrote:
           | I'd have to find the video, but some outfit did a survey of
           | all the various "extra-virgin olive oil" brands on US store
           | shelves, and found that most (not "some" - _most_ -) were
           | crap.
           | 
           | I think the issue was most were more like "pure" olive oil,
           | with food coloring.
           | 
           | Many of the pricey ones that come in small, expensive
           | bottles, were not actually what any decent European would
           | expect from the cheapest canned oil.
        
             | yumraj wrote:
             | There's an old study by UC Davis also [0]
             | 
             | [0] https://www.ucdavis.edu/news/imported-olive-oil-
             | quality-unre...
        
       | avsteele wrote:
       | A recall a number of news items from a few years ago which talked
       | about how some olive oil vendors were adulterating their products
       | with other oils. If this phenomenon could be better understood
       | maybe there would be a rapid, optical/spectroscopic way to
       | characterize olive oil purity.
        
         | vixen99 wrote:
         | Yes, if only. I continually hear that much olive is not what it
         | is supposed to be and it seems that authorities empowered to do
         | something about this don't do much to stop it or perhaps
         | they're fighting an uphill battle. In general the higher the
         | price, the more likely the product is 100% genuine. The logic
         | here might be that there's not that much profit in adulterating
         | pricey oil selling rather limited quantities.
         | 
         | For a technical delve into olive oil fluorescence:
         | https://cdn.intechopen.com/pdfs/27027/InTech-Analysis_of_oli...
        
         | kurthr wrote:
         | The simpler, cheaper, and faster you make the test... the more
         | quickly it will be defeated by the adulterators. Much like spam
         | filters and SEO, leaking anything about how you defend against
         | an attack just makes the attackers marginally improve their
         | game.
         | 
         | Simple amine/nitrogen tests for protein is how we got poisonous
         | melamine in fake milk and wheat gluten killing babies, dogs,
         | and cats.
         | 
         | It comes down to Goodhart's law.
        
           | lostlogin wrote:
           | I agree that the test becomes the target in many things, but
           | how do you suggest applying that to food safety?
           | 
           | If easy tests are out, you go to a very complex test
           | immediately?
        
             | kurthr wrote:
             | You test at least moderately close to the actual target and
             | you punish those who are breaking the rules brutally (it is
             | actually food safety!). Instead we allow Olive oil that
             | isn't and Fish that aren't because, nobody has died yet?
             | Allergies are possible even at very low levels.
             | 
             | My real point wasn't the simplicity or cheapness, but often
             | the biproduct of those is that it's a test you already have
             | that doesn't measure what you want (nitrogen rather than
             | protein). In the case of Olive oil, if what we cared about
             | was it's fluoresced color rather than the material in it,
             | that would be great.
             | 
             | If what we care about is components, random GC/IR
             | spectroscopy (perhaps after centrifuging) to see the actual
             | compounds with consequences would be a better choice than
             | the cheapest thing they can just add another weird chemical
             | to defeat.
        
               | lostlogin wrote:
               | Thanks.
               | 
               | A funny version of this is Manuka honey. It's not easy to
               | define and it's slowly turned into an NZ versus Australia
               | thing. There have been examples where bees that only gave
               | Manuka to feed on are making honey that doesn't meet the
               | standard, and bees that weren't thought to be feeding on
               | Manuka have been making Manuka honey.
               | 
               | I have seen recipes for making non compliant honey into
               | compliant honey (to be clear, the input honey is Manuka,
               | but the lab test wasn't being being passed). It's about
               | blending various types of honey.
               | 
               | It's a bit dumb in my view and needs a better test. As
               | you say, it's meeting the test, not the objective of the
               | test.
        
           | canadiantim wrote:
           | That's not entirely true. The domain within which the
           | cheating can occur shrinks by eg checking certain properties,
           | tho the problem you're talking about happens when only a few
           | properties are checked because then of course only those
           | properties need to be gamed/manipulated. It's about how much
           | coverage your tests have over the properties of what you're
           | testing
        
         | rootusrootus wrote:
         | It'd be nice to see some real testing and verification. I've
         | resorted to buying only California olive oil because I have
         | more trust in the regulation of domestic products than I do in
         | the regulation of imports.
         | 
         | It's interesting to note that California Olive Ranch's 100%
         | domestic olive oil costs quite a bit more than their 'world
         | blend.' I'm guessing that world blend includes imported not-
         | really-olive-oil.
        
       | hultner wrote:
       | Is the article published free somewhere?
        
       | throwawaaarrgh wrote:
       | Fun EVOO facts:
       | 
       | - the label of every bottle of EVOO uses short country codes to
       | indicate where the oil came from, which is often multiple
       | countries. this doesn't mean it's worse, but there are more ways
       | some part of it could have not been great.
       | 
       | - extra virgin olive oil is a juice that will go rancid from
       | excessive light, oxygen, or temperature fluctuation. it's
       | basically like red wine. once you open the bottle, use it
       | quickly, and keep it in a dark dry place. make sure the bottle is
       | glass and is darkened.
       | 
       | - high phenolic olive oil is more expensive to produce (and thus
       | buy) but contains more polyphenols.
       | 
       | - more olive oils now carry seals of authenticity. find one,
       | Google it, see if it looks legit. there are many different
       | certifications. Italy was the country with the most EVOO fraud,
       | so be more circumspect with oil from there.
       | 
       | - a list of oils sold in America certified as pure:
       | https://www.aboutoliveoil.org/79-certified-pure-and-authenti...
       | 
       | - all EVOO is cold pressed and unrefined, by definition. ignore
       | any marketing jargon you see on different bottles.
       | 
       | - don't pay a bunch of money for infused oil. buy whatever oil
       | you want, put some aromatics in a jar, pour in oil. use it up in
       | a month.
        
         | opheliate wrote:
         | Be very careful when infusing your own oil. Botulism is a real
         | concern, it is often necessary to soak your aromatics in a
         | citric acid solution before infusing.
        
       | atoav wrote:
       | Oils generally can have funny properties, like dichromatism in
       | pumpkin-seed oil (small layers are perceived green, thicker
       | layers red)
        
         | HPsquared wrote:
         | Similarly, yellow food colouring looks red when concentrated.
         | Also water looks blue but deep underwater there's no blue light
         | left. Beer's Law
        
           | dylan604 wrote:
           | There's a yellow mica pigment that when used in soap making
           | it turns a very reddish-orange (almost like rust) until the
           | saponification has completed and then returns to yellow. It
           | is very disheartening the first time you see it and start to
           | think how your batch of soap is going to not be what you
           | hoped, and then 24 hours later it looks exactly how you
           | hoped.
        
             | kshacker wrote:
             | As someone who has used only white soap for decades, so
             | quite ignorant, could you provide a name?
        
               | dylan604 wrote:
               | Of the mica? There's probably others, but I have direct
               | experience with Lemon Cupcake from Mad Micas
               | 
               | https://www.madmicas.com/products/lemon-cupcake-
               | mica?_pos=5&...
        
             | HPsquared wrote:
             | I wonder if that has something to do with the pH.
        
               | dylan604 wrote:
               | That would be my guess as well. After thinking about this
               | further, I do remember as a kid using the kits for dying
               | eggs for easter (somewhat belated topic) that required
               | vinegar instead of water. The yellow dye would also
               | appear orange until it dried as yellow. So, yeah, I'm
               | leaning towards the pH as to the cause, but we still
               | don't know the reason. I'm going to deliberately _NOT_ go
               | down that rabbit hole...*
               | 
               | "An acid-base indicator is an organic compound that
               | changes color with a change in pH. Methyl orange is a
               | very common acid-base indicator, red in solutions that
               | have pH values less than 3.2 and yellow in solutions with
               | pH greater than 4.4. Indicators change color because the
               | chromophoric system is changed by an acid base reaction
               | (see below)." https://chem.libretexts.org/Ancillary_Mater
               | ials/Laboratory_E...
               | 
               | * I swear I tried really hard. Luckily, the hole wasn't
               | too deep
        
       | stared wrote:
       | Quinine is another fluorescent substance - it glows blue in UV
       | light. I used to carry a UV diode into malls to test if tonics
       | contained quinine.
        
         | lostlogin wrote:
         | What did you find?
         | 
         | I believe most use a synthetic version. I've only had the
         | natural one a few times and it was quite different, but the
         | drink wasn't as sweetened so that might have been the
         | difference.
        
         | cialowicz wrote:
         | Curious, was this a hobby or did you work for the government
         | tonic inspection bureau?
        
           | hinkley wrote:
           | All gin drinkers are members of the tonic inspection bureau.
        
             | UmYeahNo wrote:
             | Gin drinkers, too
        
               | hinkley wrote:
               | Err, yes.
        
       | robert_tweed wrote:
       | I don't have a green laser, but I just tried shining a 365nm UV
       | torch on the various bottles of oil in my kitchen.
       | 
       | My good EV olive oil in a glass bottle goes a sort of pinkish
       | colour. With the natural colour of the oil & the way the glass
       | reflects/refracts light, it makes it look like copper.
       | 
       | I don't get the same effect with cheapo refined olive oil in a
       | plastic bottle. I get a bit of fluorescence - the normal violet
       | colour and much less than say a white piece of paper - but all or
       | most of that is just from the container.
        
         | is_true wrote:
         | What happens if you put some of the cheap oil in a different
         | container and then shine it with the torch?
        
           | teekert wrote:
           | This is science. Do it first before you bring the torch to
           | the supermarket ;)
        
         | detrites wrote:
         | Interesting. I wonder if this technique could be used as an
         | olive oil purity/quality test of sorts? Maybe correlating a few
         | samples of various kinds, along with some external form of
         | verifiable testing, it may be possible to figure it out.
        
           | robert_tweed wrote:
           | I'm definitely taking my UV torch to the supermarket next
           | time. However, most good olive oils come in dark glass
           | bottles, so I don't think it will be possible to check those.
           | Might be interesting to look for variation among the cheaper
           | EV ones.
           | 
           | The article mentions differences between brands, but IDK if
           | there's a specific correlation with quality other than that
           | fake olive oils certainly won't turn red/pink.
        
             | kjellsbells wrote:
             | I think your instinct is right: the dark glass is going to
             | negate any test.
             | 
             | I always assumed that products like olive oil sold in thick
             | green bottles were sensitive to degradation by (UV,
             | sun)light, so if that is true then by definition a casual
             | in store test is not going to work. But perhaps green
             | bottles mean nothing vis a vis light.
             | 
             | I do recall that brown bottles were a thing in brewing to
             | prevent beer from becoming funky by the action of light,
             | but perhaps oils aren't susceptible to that.
        
               | shirleyquirk wrote:
               | Olive oil absolutely degrades in light. Even in dark
               | bottles. Really high quality olive oil is sold in opaque
               | ceramic containers.
        
               | wil421 wrote:
               | It's the same as beer. Light degrades the beer or oil. My
               | olive oil research says a lot of cheap oils are already
               | going rancid by the time you buy them. Very good quality
               | bill oils, like Costco's EVOO, will go rancid before you
               | can use it all.
        
         | great_tankard wrote:
         | Make sense. Plastics are notorious for absorbing in the UV
         | range- for most useful spectroscopy experiments below ~400 nm
         | we have to go straight to quartz cuvettes.
        
           | jrockway wrote:
           | Recommended video if you want to dive deeper into UV
           | absorption: https://www.youtube.com/watch?v=vwsHRrDYu5o
        
       | ProllyInfamous wrote:
       | Other fun household items which will fluoresce under UV light:
       | 
       | Your feet (athlete's foot) and sometimes hands.
       | 
       | Banana "mold" (the black spots' edges).
       | 
       | Your credit cards and IDs (usually a bird on VISA and "AMEX" on
       | so-named).
       | 
       | Money (embedded denomination "strip" is different for each modern
       | bill).
       | 
       | Centipedes and Scorpions (seriously, just go into your yard at
       | night and scan the ground for wigglies).
       | 
       | If you have beehives, the Varroa Destructor (species/pest) also
       | shines brightly on their little carapaces.
        
         | jrockway wrote:
         | Getting way off topic, but if you hit ordinary peanut butter
         | with strong light, it glows afterwards. Go into a very dark
         | room, adjust your eyes to the dark, look away with your eyes
         | closed/covered as you hit a jar of peanut butter with a camera
         | flash (not the household item it once was, sadly), and then
         | look at the peanut butter. It's glowing!
         | 
         | I heard this on the Internet and didn't believe it, but tried
         | it for myself, and yup. It glows.
        
         | dehrmann wrote:
         | I'd add turmeric.
        
           | sdwr wrote:
           | Turmeric glows???
        
         | littlestymaar wrote:
         | I'm surprised not to see tonic water in this list.
        
         | qwezxcrty wrote:
         | An addition: Human urine.
         | 
         | This can be useful when inspecting the cleanliness of toilets.
        
         | echelon wrote:
         | Things that obviously fluoresce under normal visible light
         | conditions can turn much more brilliant under visible laser
         | light (eg. 532 nm green)
         | 
         | Orange and green fluorescent dyes (such as on tennis balls),
         | white clothes washed in detergent, etc.
        
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       (page generated 2023-04-15 23:01 UTC)