Optical Brighteners in Polymer Clay

In all the reading I’ve done about polymer clay, I don’t think I’ve ever seen any mention of optical brighteners in polymer clay. But they’re there, clear as day, and yet hidden. Sort of. Today we’ll have a bit of a science lesson and then I’ll introduce you to a characteristic of your polymer clay…yes, the very same clay you have right now…that you likely didn’t even know was there. Your polymer clay glows. Intrigued? Read on…

What are Optical Brighteners?

First a little lesson about light. Light is an electromagnetic energy that is produced in different wavelengths. Light of a specific wavelength is perceived by our eyes as a certain color. As you can see in the picture below, light at 400 nanometers (that’s 0.0000004 meters) is visible to your eye as a purple color. And yellow light is around 600 nm. Notice that ultraviolet is merely violet light that is just beyond the limits of our eyes. The same goes for infrared, which is just beyond red, in the region where our eyes can’t see it. (Your TV’s remote control uses infrared light…you can’t see it, but your camera’s sensor can. Try it!)

Visible light is only one small part of the electromagnetic spectrum.
Diagram is by ScienceBlogs.com

In general, when light falls on a colored object, all other colors are absorbed, but the “right” color is reflected and therefore visible to our eyes. So a green ball absorbs all wavelengths of light except for light of 570 nm or so. That light is then reflected back to our eyes and we see a green object.

Now the next science term for today is fluorescent. Fluorescent things absorb light or energy of one wavelength and emit it as light of a different wavelength. Fluorescent light tubes absorb electrical energy and emit it as visible light. That’s how our most common light bulbs work today. And fluorescent paints absorb light from the ultraviolet region of the spectrum (such as the light from a black light) and emit that back to us in wavelengths that are visible to us in the visible spectrum.

Optical brighteners are a fluorescent dye that has the ability to absorb light at 340-370 nm (ultraviolet) and emit that light energy at 420-470 nm (visible). This means that optical brighteners absorb light that we can’t see and emit it as blue light that we can see. They don’t, however, glow in the dark. Fluorescent dyes merely “re-emit” light as another color. When the lights go out, they stop emitting light.

Why Use Optical Brighteners?

Do you remember years ago when little old ladies had blue hair?  You see, white hair naturally turns yellow with age, so they would rinse their hair with something called bluing. Bluing is a blue dye that, when used in a diluted rinse, counteracts the yellowing and made their hair appear more white. Bluing was used as a laundry rinse for the same purpose. It makes white clothes whiter.

Optical brighteners are the modern equivalent of a bluing rinse. They’re added to laundry detergent and that’s the real reason that your white shirt glows bright white when you go somewhere with a black light. Not all white things glow under black light…just the ones which have optical brighteners added. Optical brighteners don’t just glow in black light, however. Because they absorb light that in the ultraviolet region of the spectrum (that we can’t see) and then emit them in the visible spectrum, there is actually more blue light coming from a treated object than there would be otherwise. To our eye, this object will appear brighter and whiter, even in regular light. In bluish light, such as in the shade, this can be quite obvious, in fact.

Optical brighteners are actually quite common in our world even though you may never have heard of them. They are the magic ingredient in whitening toothpaste, brightening shampoo, and under-eye makeup that “brightens” your skin. Ordinary copy paper is also coated with an optical brightener to make it appear even more bright white.

Optical Brighteners in Polymer Clay?

Yes, you probably guessed by now. An optically brightening fluorescent dye is present in some brands and colors of polymer clay as well. Have you ever wondered what the difference is between Premo Translucent and Premo White Translucent? They’re equally clear, but one is more yellow than the other. Now you know why that is! And not surprisingly, if you compare samples of those two Premo colors under black light, you’ll see that one glows brightly and the other appears dark.

Premo translucent and Premo white translucent differ in that one contains a fluorescent dye that makes it look more white. Learn more at The Blue Bottle Tree.

Which Polymer Clays Contains Optical Brighteners?

Not all brands of polymer clay contain these fluorescent dyes. None of Kato’s colors seem to contain them. And only some of Premo‘s do. I only have so much clay on hand and short of going out to the store with a black light, I can’t test a large variety of colors. But I can show you what happens with the whites and the translucents of most of the various brands because I’m lucky enough to have them here. Here is a comparison of various brands of white and translucent polymer clay.

Some brands of white polymer clay contain a fluorescent dye called an optical brightener to make it appear more white. Learn more at The Blue Bottle Tree. Some brands of white polymer clay contain a fluorescent dye called an optical brightener to make it appear more white. Read more at The Blue Bottle Tree.

Some Liquid Polymer Clays also contain a fluorescent dye. As you can see in this picture, Fimo Deco Gel contains a lot of it, Liquid Sculpey contains a lesser amount, and Kato Liquid Polyclay doesn’t seem to contain any optical brightener.

Liquid Fimo and Liquid Sculpey both glow under black light, but Liquid Kato does not. More at The Blue Bottle Tree.

The dye does not break down with normal baking of polymer clay. Baked clay still glows as brightly as unbaked clay under black lights. And because the optical brightener is a dye and not a pigment, it does diffuse through unbaked (and possibly baked) polymer clay over time. When I left a piece of unbaked Premo white sitting on top of an unbaked sheet of Kato white for a week, I came back to a glowing spot in the middle of my Kato sheet. I couldn’t see it in regular light, of course, the effect was too small. But under black light there it was, like a bleeding glowing stain!

How Does this Differ From Glow in the Dark Clay?

Glow in the dark pigment is phosphorescent, which means that it will absorb light, store it, then release it over time. There are many glow in the dark polymer clays, all of which are translucent polymer clays which contain particles of phosphorescent pigment. Glow in the dark clays are also fluorescent and do emit light under black light. It is also a property of the phosphorescent pigment.

There are several brands of polymer clay which carry a glow in the dark color in their range. Sculpey III carries a glow in the dark kit that includes mini-bars of four colors of glow clay plus black and white. Sculpey III also carries a full-sized bar of neutral “glow in the dark” color. Cernit and Fimo both carry a glow in the dark color. And there is also a glow in the dark color of Pardo Jewellery Clay called Luminescent. There are lots of choices!! You can also make your own glow in the dark clay by adding glow pigments to translucent polymer clay of your choice (such as Pardo Art Clay). Read my article about DIY glow in the dark clay.

Can Optical Brighteners Affect your Clay Project?

Does it really matter if your polymer clay contains optical brighteners? Actually, yes, it does. In fact this is how I found out about it. I started my polymer clay life as a fervent Kato Polyclay fan. (I still love the stuff.) And I did a lot of work with millefiori canes with translucent backgrounds. Other clayers, however, raved about how much more clear “Premo with Bleach” was. (Premo with bleach was the term the polymer community used to use for the color that eventually became Premo Frost and is now Premo White Translucent.) I bought some. I tried it. And I hated it.

It was a bit more clear, yes. But it also had a funny color cast. It looked sort of a funny glowing purple color in some light. I began to notice how some of my translucent creations had this funny glow and yet others didn’t. When I look at these pieces in bright sunlight they look great. But when in shade (like when standing at my kitchen sink, sanding in front of the window), I can see this funny color, almost a glow. One day while doing laundry I noticed that the detergent had the same glow. And I got busy researching it. And sure enough, there is fluorescent dye in both.

Optical Brighteners in polymer clay can make a difference in your project. Does your clay have this fluorescent dye? Learn more at The Blue Bottle Tree.
You can see the effect of the fluorescent dye in this picture. The bead was made with Premo White Translucent. The picture on the left was taken in indirect natural light outdoors. The picture on the right was taken in a lightbox. I did color correct the photograph to compensate for the color difference in the light. Even so, you can still see the blue-purple color cast of the fluorescent dye in the one on the left.

But the presence of the optical brighteners in the clay isn’t going to have much of an impact most of the time. If anything, it will do exactly what it was designed to do. Your whites and translucents are going to be more white and less yellow.

Also, remember, that some colors of clay contain other fluorescent pigments. The bright pink, orange, and lime “day-glow” colors will glow under UV light. But have a look at your other colors as well. I noticed that many of my clay colors glowed in black light and some of my mokume gane pieces were truly stunning! Here are some pieces you might recognize from my Sculpey Souffle review.

Many colors of polymer clay contain fluorescent pigments that glow brightly under black light. Learn more at The Blue Bottle Tree.

Can you use this feature to your advantage? Absolutely! In fact, I have one word to say to you. Halloween. Think of all the black lights that show up this time of year! Polymer clays with fluorescent dyes and pigments in them will glow bright under black light, regular clay will not. How many ways can you think of using the glow power of these clays to create a design? Here’s more

Sources: PVClay was provided courtesy of PVClay Brazil. Sculpey Souffle was provided courtesy of Polyform.

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40 thoughts on “Optical Brighteners in Polymer Clay”

  1. Hi. Thanks for the post. I had noticed that colours other than fluorescent colours glow under black light. Cheers

  2. Pingback: KatersAcres UV Reactive Polymer Clay Challenge Entry

  3. I too have noticed this and wondered why the color change was so drastic with some pieces.. I had thought it was the lighting, not the clay. I notice it most with colors that were mixed up and meant to be seen as brown hues (brown in bright sun, purple in shade, just as you mention above). Never thought about the use of brighteners, but it makes absolute sense! I’m happy you’ve solved the puzzle and really glad that you shared your findings here! Another brilliant post! Thanks a bunch!

  4. Wow !! This is really interesting stuff and just in time for Halloween too !! I think I’ll need to grab a portable Black light bulb and create some Halloween themed critters using the Black Light responsive clays and place them on a table under a Black Light to give off a eerie glow at night to display.

    1. Hi again,
      Have a look at “IrishSusco” on Etsy her pendants are stunning.
      I fell in love with as soon as I saw them.

  5. Hello,
    Thanks again for another very interesting article.
    It was only a fewa weeks ago I say some polymer clay pendant on etsy that glow after they had been exposed to a special(probably UV light) they were fantastic and so beautiful for evening wear.
    I only use Kato clay(mores the pity) but will think about trying another brand as I have some very different types of cameos planned.
    thank again for your wonderful research and for sharing.

    1. There are a couple Etsy seller who use glow in the dark clay in their work. Some are really gorgeous, too. I mix brands all the time, so there’s no reason you can’t pick the clay color that works for what you want to accomplish, and still stick with Kato for the rest of the project. (and you can cure at Kato temps, too, just keep it covered during baking to help prevent any browning)

  6. Hi, thanks for a great informative post! I immediately wonder though, what chemical is used as the optical brightener and are there any hazards? I have been attracted to Pardo because of the beeswax base and general claim of ‘naturalness’ (I’m also a beekeeper so the effect of things on the environment is close to heart :). Can you shed any light?

    1. It’s a really good question. It’s something that’s broadly used in cosmetics so if it were harmful I think there would be more of an outcry about it. I’ve not read anything about it being harmful. But, of course, there are so many un-explored risks that we have around us all the time. I did find this link: http://www.seventhgeneration.com/learn/videos/no-glow, but keep in mind that Seventh Generation makes natural cleaning products so they’re also invested in taking that stance. Here’s another article: http://livinggreenmag.com/2012/11/26/home-garden/optical-brightener-hazards-in-your-laundry-detergent/. Now these articles address the chemical being on our clothes and sheets and ultimately our waterways and environment, which is a very different thing than being locked inside of polymer clay. Even if they are harmful in waterways, for instance, it doesn’t mean it would be harmful in polymer clay. It’s all very untested an unknown. But I didn’t see anything that is scary or particularly ominous in the research I did. Sorry, I don’t have answers on this one!

      1. 🙂 yes, I did find a few bits of info on optical brighteners but they seemed from sources that had an agenda to push. I think your point about it being locked in the clay is important. And when baked, I’d bet it wouldn’t leak or leach out like you described on unbaked.
        I just glanced at your new post on uses – love the hidden messages idea!!!

    1. It’s really dramatic, isn’t it? For a warm colored pendant like that, it’s really discordant and unattractive. Regular Premo trans would have been a far better choice. For cool colored pieces, though, it might not matter so much. But it’s sure valuable to know isn’t it?

    1. Interesting! I do know that flowers do, because bees can see UV. But come to think of it, this makes sense. Think of how utterly electric the yellow leaves are on a rainy day. I wonder what the wavelengths are on those. Oh now you have me curious.

  7. Thanks a lot Ginger… you are smart and so generous too. I love reading your blog… packed full with useful and reliable information. And now… another new information about optical brightener, fluorescent dye… that 5 minutes ago I didn’t know they’re exist!!! Thank you (hugs 🙂 )

  8. María Teresa Lefler Camino

    Interesante artículo, gracias por la publicación. Aprendo mucho de sus investigaciones…

  9. LOVE your blog! Thanks for another super duper article. It’s good to know about the brighteners and the glow in the dark. My clay pal in England once sent me the cutest little owl. It sits on my table in my studio. one night I went in there to get something and there was Cheeky glowing at me. Scared about 13 years growth out of me as I didn’t know that little Cheeky had glow in the dark eyes. 😀 For some reason my pal thought that was a scream. ;D

    1. Have you had a chance to work with Souffle yet? It’s a strange clay, very different from the others. It’s very opaque. Now this is purely my speculation, but I think that whatever they’re using to make the clay be more “suede-like” is a particle of something (think cornstarch, but fluffier). And that would therefore block the light. When I reviewed Souffle, I did notice that it’s far more opaque than the other brands.

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