Do You Have to Seal Polymer Clay?

Do you have to seal polymer clay? When is it a good idea, and when can it ruin your work? Learn more at The Blue Bottle Tree.If you read or follow any polymer clay groups and forums, you’ll notice that one of the most common questions asked is “Which polymer clay sealer should I use?” Everyone has their favorite sealer, and the answers differ depending on your need and the availability of products where you live. But perhaps we’re asking the wrong question. I think the first question needs to be, “Do You Have to Seal Polymer Clay?”

Do you have to seal polymer clay?

  • You don’t have to seal polymer clay. Baked polymer clay is durable plastic and therefore more durable than any sealer.
  • Sealers and varnishes will not prevent breakage. If your projects are brittle, address your baking process.
  • Use a varnish to protect fragile surface treatments such as chalk, pigment, or mica.
  • Use a varnish to change the gloss level of your project.
  • Many varnishes make polymer clay sticky. See here for more info.
  • Spray varnishes are nearly always incompatible with polymer clay.
  • For a glass-like finish on plain polymer clay, sanding and buffing is an excellent option.

When to Seal Polymer Clay

People often want to seal their polymer clay creations for protection against the elements or from damage during use. In most cases this is unnecessary. Once it’s been properly baked or cured, polymer clay becomes a durable solid plastic that is waterproof, shock resistant, and fairly tough. Because it’s such a durable material, it probably won’t surprise you to learn that it’s actually more durable than any sealer that you will put on it. Sealers, varnishes, and finishes do have their purpose, but bare clay itself does not need to be sealed for protection. Here are some reasons why you would want to seal polymer clay:

Protect Surface Treatments

When you embellish your polymer clay project with chalks, paints, mica powders, metallic pastes or metal leaf, those treatments are sitting on the surface of the polymer clay and are not nearly as durable as the polymer clay itself. Projects using surface treatments must therefore be sealed for maximum durability. In the case of jewelry, the wearer must also be protected from any pigments, dyes, and mica coming off on their clothes or skin. If the project is purely decorative and will merely be sitting on a shelf, sealing is not imperative. But keep in mind that cleaning any accumulated dust would likely cause the surface treatments to be disturbed.

Polymer clay artists often use acrylic paint to color and embellish their projects. Does acrylic paint need to be sealed? Well, it depends. Paint used to antique a textured surface is mostly rubbed off and the remaining paint is fairly well protected down in the “nooks and crannies” of the piece. In that case I would not seal it. But thin layers of acrylic paint can sometimes peel or scrape off, or will come off if the piece is washed. In those cases I would use a sealer. Even when the layer of paint is thick and strong, a sealer might give a brighter, more durable coating much in the same way that a clear coat is used over the colored paint on your car. You’re going to be the best judge for your own particular project.

Change the Gloss Level

Although different brands of clay have different native gloss levels, and the technique you use can leave you with a matte or glossy surface, the easiest way to change the gloss level of your finished piece is to use a sealer that has the desired type of gloss level. Many varnishes come in both glossy and matte varieties. Sometimes you will look at a finished piece and realize that you would like it better matte or glossy and choosing the correct varnish can easily give you the effect you want.

Ease of Cleaning

Polymer clay is not porous like wood or unglazed ceramic. It will not absorb and hold water. Polymer clay can, however, have fine pits in the surface, depending on the method you used to create the piece. Some clay brands, such as Sculpey III and Souffle, tend to have a surface that appears to be porous (this is also why those brands are so great for holding onto acrylic paint). Because of this, dirt and makeup may be difficult to remove from a piece without scrubbing with soap and water. This can also be a problem when clay is created with a finely textured surface. Plus, sometimes the dyes in your makeup can permanently discolor light colored clay beads. In these cases, sealing the clay makes sense.

Intensify Colors or Translucency

Just like a pebble dipped in water becomes more vivid and bright, a coat of sealer can make polymer clay appear more rich, deep, and colorful. This also holds true for translucent clays. They will appear even more translucent when a sealer is used on the surface.

When NOT to Seal Polymer Clay

Sealers and varnishes are wonderful tools to be used when the time is right. But there are reasons why trying to seal your project might not be a good idea. Here are a few reasons.

  1. Many sealers, varnishes, and coatings turn sticky or cloudy over time, ruining your project. What works for one person might very well not work for another. Unless you know how your chosen sealer is going to act, and unless you’re certain you need to be using a sealer in the first place, it might be better to reconsider. Always test some samples before using a sealer on something that’s irreplaceable.
  2. Because most polymer clay varnishes are, themselves, a kind of thin plastic coating, they can often be peeled from the project if you try hard enough. If the product will get lots of abuse, a varnish might not be strong enough.
  3. When making glass-like items, using a gloss sealer is not a substitute for creating a smooth item in the first place. Applying a glossy coat over the top of a project full of tool marks and fingerprints will just accentuate them rather than camouflage them, making your project look sloppy and unprofessional.
  4. Using a sealer on a highly textured item can go badly wrong. I remember waxing my dad’s pickup when I was about 10. I got wax on the black plastic trim. Of course it turned white in the grooves. Bad memories! Polymer clay is no different. Wax is great for smooth surfaces, but it will collect in the small crevices of a textured item and look awful. Liquid varnish such as Varathane will also collect or pool in highly textured areas, leading to a look that very much wasn’t what you had in mind. You can seal textured items with a varnish, but you have to be careful in your application. Don’t just slather it on!

Use the Right Sealer for your Project

There are lots of types of polymer clay sealers and glazes. I use a different sealer depending on the effect I want to accomplish in my finished piece. There are many excellent varnishes, finishes, and sealers out there, and I haven’t tried them all by any means! But here are some tried and true sealers that I can heartily recommend.

Glossy Sealers

Varathane is a brand name of polyurethane varnish available in the US. It has been a favorite varnish with polymer clay artists for many years. It does come in gloss, semi-gloss, and satin, but I find that even the satin is still pretty glossy. I wrote an article about Varathane describing why it’s my favorite sealer and giving sources (including non-US brands of polyurethane).

Pearl Ex Varnish is made by the same company as the well-known mica powders. But this is just a varnish. It works nicely on all brands of clay, but doesn’t give a super glossy finish.

Aleene’s Jewelry Pendant Gel is a glossy dimensional glaze that can be used on most clays, but avoid using it on Fimo as it can get sticky.

Epoxy Resin is a clear, thick coating that is gaining popularity among polymer clayers, for good reason. It is exceedingly strong and durable, more so than any other finish. But it has a long cure time, takes some practice to get used to using, and is known for causing swear words. But once you get the hang of it, it works very nicely. Favorite brands are ICE Resin, Envirotex Lite, and Magic Glos (a brand of UV-cure resin).

Kato Liquid Polyclay can be used as a sealer. Just brush or sponge on a thin coating and then cure in the oven. After oven curing, you can use a heat gun to further cure it to give a crystal-clear, glossy finish.

These finishes work well to create a glossy surface on polymer clay.

Matte Sealers

Translucent Liquid Sculpey is another brand of liquid clay but this has a matte finish when cured. To get this effect, use a cosmetic sponge to dab the TLS onto your piece, then oven cure. Do not cure with a heat gun or the effect won’t be matte.

Cernit Matte Varnish gives a nice, smooth, dry finish on all brands of clay. It’s not terribly matte, but does give a low-sheen satin finish that looks and feels great.

DuraClear Ultra Matte Varnish is a dead matte varnish that has no sheen at all. It performs beautifully on all brands of clay except for Kato.

If you do need to seal polymer clay, these products work well to create a matte finish.

For a Natural, Burnished Look

If you like the look and feel of polymer clay that’s been sanded to a very high grit and buffed, you will love the way that adding a coat of wax makes those pieces feel and look. Renaissance Wax is a favorite brand of high quality wax that has a great marketing program and a price tag to match. Don’t get me wrong, I love Ren Wax. But want to know a secret? Paste Wax and Neutral shoe polish will work just the same and have a MUCH better price. Remember, wax doesn’t work well on items with a fine texture (such as when you use sandpaper or a sponge to disguise fingerprints). The wax will collect in the pits and look awful.

Renaissance wax functions exactly like paste wax for use on polymer clay. But it's much cheaper.
I left the sticker on the Renaissance Wax so you could see the cost. The paste wax is an old can I stole from my dad. I don’t think Minwax even makes it anymore. But Johnson’s Paste Wax is readily available and does the same job. Cheaper.

For Sealing Delicate of Textured Surfaces

Sometimes the act of brushing or rubbing on a sealer can disturb surface treatments such as mica powders. And a sealer can actually dissolve the surface treatment, like happens when you put Varathane onto alcohol inks. And sometimes you do want to seal finely textured surfaces without getting air bubbles or pooling. In these cases a spray varnish would be great, but most spray varnishes can cause polymer clay to become sticky over time. There are two brands of spray varnish that are completely clay safe and really gives a great effect. PYM II is one brand, and Helmar Crystal Kote Matte is another. They sets and stabilizes mica powders and can help seal alcohol inks with a quick, light coat. After that, you can layer subsequent coats to give a thicker seal or you can use another type of sealer. Yes, you can use Varathane or Ren Wax over the top of PYM II and Helmar.

PYM II polymer clay spray sealer is safe for polymer clay. Read a review at The Blue Bottle Tree.

Sealers to Avoid

Just as there are good sealers on the market, there are also some bad ones. Keep in mind that many of these have been used by many people without any ill effects. But they are also known for having unsatisfactory results as well.

Future Floor Finish, which is now called Pledge Floor Care (and is very similar to the European product Klear) is a very clear, thin, watery finish that is favorite of beginning polymer clay artists. It gives a nice glossy finish, dries clear, smells great, and is readily available. I used it when I first started and I don’t really have much bad to say about it, except that it’s not very durable. There are better options, such as any of the sealers I mentioned above. It’s still a good sealer for things that won’t get any wear, such as figurines and models. But for jewelry, it just dulls down way too fast.

Liquitex Varnish, which I have previously recommended, is an artist’s varnish that comes in gloss, matte, and satin finishes. My tests show, however, that it has lots of brush strokes, turns cloudy on dark colors, and is sticky on some brands of clay. There are better options, such as Varathane or Pearl Ex Varnish.

Dimensional glazes are thick, clear one-part glazes which can be applied thickly to create a glossy, glass-like finish. Some are better than others, but all of them can turn cloudy over time. I think that humidity is a factor. Some brands are Triple Thick, Diamond Glaze, Dimensional Magic, and Aleene’s Jewelry and Pendant Gel. I have found that all of them turn sticky on at least one brand of clay. Aleene’s did show good results on every clay besides Fimo, however, so you might try it. For every person who recommends Triple Thick, I read of another one who says it gets sticky or cloudy. And the reviews I’ve read of Dimensional Magic are sad. I don’t like reading of people’s projects being ruined by a material that was used properly! Success is just too variable with these glazes for me to recommend them universally, aside from Aleene’s.

Nail Polish is often recommended as a paint or glaze by articles in craft blogs. Almost always there will be tears later because the plasticizer in polymer clay softens the polish, making it turn gooey over time. That is, if it dries at all. The thing is, it can be rather hit and miss, perhaps due to the brand of clay or nail polish. It does work often enough that people not knowledgeable in polymer clay will not see what’s wrong with recommending it, and the next person isn’t so lucky! If I had a dollar for every email I answer on this one….

Oil-based Varnishes will often work on polymer clay but will yellow noticeably with time. Cindy Leitz tested Minwax oil-based polyurethane and found that there were no compatibility issues with polymer clay, but it did yellow. This is most noticeable on white clay, of course. Cindy’s result does show the value of testing and making samples. Don’t just randomly grab any can of varnish from the hardware store shelf.

Mod Podge is a glue and decoupage medium that crafters have relied on for working with paper for as long as I can remember. Craft blogs also sometimes recommended it as a sealer for polymer clay.  Just don’t do it. No. Mod Podge is actually made from the same stuff as plain white glue. It’s not a real sealer. You wouldn’t coat your beads in glue, would you? Again, some people have good results with this. But for most of us Mod Podge gets sticky and cloudy in humidity. Just say no.

Spray sealers can also have unpredictable and disappointing results. Sometimes the finish never dries, other times it turns soft and sticky months later. It seems that the plasticizer in baked polymer clay can soften the spray varnish, so even a good trustworthy brand of liquid varnish might not work so well in the spray form on polymer clay. If you need a spray, do yourself a favor and order some PYM II. It’s one of the few sprays that I know of which is absolutely safe to use with polymer clay. Your mileage may vary, of course. I tested 10 different brands of spray sealers and found that only PYM had universally good results on all the brands of clay that I tried.

Sealing Myths

New clayers often assume that polymer clay needs to be sealed to protect it against water damage. Cured polymer clay is waterproof and does not need to be sealed against moisture. Most sealers are not fully waterproof (they’re merely water resistant) and can be damaged by prolonged contact with moisture. (A quick wash is not usually a problem for a sealer, though.) If you’re using polymer clay to decorate the outside of drinking glasses, you do not need to seal the polymer clay to make it safe for washing. You do, of course, want to hand wash any decorated glassware, but that’s true for any hand-embellished glassware. Dishwashers can be pretty harsh.

If you’re making polymer clay for use in aquariums or outdoors, a sealer is not only unnecessary but will most often deteriorate well before the clay. Polymer clay is weatherproof and will not crumble or fall apart after exposure to the elements (see the picture of my hearts, below). But the color of some clays can fade in sunlight. I would like to say that a UV sealer will protect your work, but I do worry about the durability of the sealer itself in outdoor conditions.

Another myth is the belief that a sealer will protect a weak polymer clay sculpture against breakage. A coating of varnish or sealer will not make your piece stronger. It will not prevent pieces from breaking off. If small pieces such as ears or arms are not properly adhered in the first place, a coat of sealer will not help things stay in place. The first time the piece is dropped or roughly handled, the ears will snap right off. I suppose if you coated a piece in a thick layer of resin, it would offer structural support. But it would also look pretty gloppy.

These polymer clay hearts have been outside in my back yard for 10 years. The finish has worn off, but the clay is in good condition.
These polymer clay hearts have hung from pots in my back yard for the past 10 years. They were made with Kato. The white one is pearl with no finish, you can see the mildew that’s grown on it. The other three are covered with Pearl-Ex and sealed with Future. As you can see, the finish has crackled and worn off, but the clay is just fine. I think we should use polymer clay more in outdoor projects. Just remember that the sealer will not hold up as well as bare clay will.

Tests and Samples

Regardless of what anyone tells you, though, it’s always best to test any new materials or techniques yourself before you commit to using them with a large or special project that you have put a lot of time into. That way you find out about the problems before anything gets ruined. For instance, Varathane is a fantastic sealer. But you have to learn how to apply it without creating bubbles, and the best way to do that is to do some tests and see what works best for you. Each sealer that I do recommend will come with its own quirks and challenges. Testing and doing sample pieces will help you find the best ways to use them.

Also remember that if you’re selling your work to others, your reputation as an artist depends on the long-term quality of your work. You owe it to yourself and your customers to make sure any sealers you use will hold up over time. Here’s a great article by Staci Louise Smith about how important it is to test your jewelry before you sell it to a customer.

And now I have a favor to ask of you. If you’re reading groups and forums where beginners are dealing with the frustrations of a badly chosen sealer, would you mind pointing them to this post? Maybe we can get the word out there and prevent some sticky beads!

248 thoughts on “Do You Have to Seal Polymer Clay?”

  1. Thank you for this website, very useful!

    But I do have a question:
    I understand the need for a sealer when adding mica powders ON the clay, but is it also needed when the mica powders are mixed IN the clay before baking. Like with the pearl clay straight from the package or kneeding PearlEx powders through the clay.

    I think I saw a shiny buffed mica shift example, that was not coated but high gloss buffed only, on this site.

    Thanks!

  2. Hello! Thank you for writing and sharing this information. I have been sculpting with Super Sculpey for the past 25 years and I wish I had this type of information back when I started. I don’t recall what brand of clearcoat that I had used, but yes, the results were as you stated … tacky to the touch and when the pieces were exposed to high humidity, they felt like they had just been freshly coated!
    Thankfully though the day finally came when I did happen to find a product that works excellent on my work. In your comparison article, you had tried a product by the same company, but the results for you did not turn out well. I use the Krylon Matte Finish spray. I use pastels on my Super Sculpey artwork so a protective coating is a must. However, for my work I want zero sheen … the more natural look the better in my case. The Matte Finish by Krylon works perfectly…no sheen at all, non-yellowing, and absolutely no tackiness no matter what the weather conditions are. Very pleased with this product.
    After the clay has cured and cooled off, I use just regular old acrylics watered down a wee bit and apply a wash over the clay and after that has dried fully, I dry brush on the pastels, then spray two light light coats of the Matte spray … making sure the piece dries for at least 15 minutes before I put the final coat on.
    Recently I had run out of Krylon and had to be setting up my booth at an art show that evening, so I had to go with a different brand. The only other matte coating the store carried was by Rustoleum. The product went on thick and heavy and was anything but MATTE!!! It was slow to dry and I had feared that I had ruined every piece.
    I set up my booth at the show that evening, but I kept that batch of work at home to give the top coat more time to set. I was very relieved the next morning when it did feel very dry to the touch…even though it looked like it just got out of a shower! ggrr. I have one item left from the show…one that had been from that Rustoleum batch, and so far its staying dry…no tackiness. The spray seems to be holding too as far as adhesion. I will never buy it again no matter what, but compared to that disaster years ago, the product was better!!
    Well thank you again for your informative article and I hope my input on my experiences and conditions with Krylon Matte and Rustoleum will shed added light on two other products.

    Take care!! Dawn M. Dodge

    As I just gave up my website on the 12th of this month …. I won’t be able to give you my web address on the form below as requested, but if you care to join me on my FB Wood Spirit Studio Page, I would be delighted. The page is new so not much happening on there so far, but hopefully this winter I will have time to remedy that. Just search for Wood Spirit Studio. 🙂

  3. We do a lot of Cornhole boards and Barn Quilts. Most polyurethane yellows. We get Sherman Williams / Helmsman / Minwax / indoor / outdoor / water based (not oil) / clear gloss or matt / urethane. It looks milky white but drys clear. As far as our barn quilts, they have been outside for 5 years and still looks like the day they bought it. It’s expensive but it will last you a life time. Only don’t dip the brush in because it will ruin your urethane. Put some in a cup and if you don’t have enough add more. Once you have used the what is in the cup, don’t pour back. I do jewelry and my husband does the wood. Our site is just about wood but I’m sure this would work.

  4. I am SO glad I found this article!

    I spent about a week’s worth of time creating an armature and covering it with Crayola Model Magic, only to find out tonight while beefing up some parts (I’m sculpting hands for my banshee) that subsequent layers cause the first layers to soften back up and peel off.

    I was so frustrated I threw the hand away. But then a friend who is in the BJD community suggested Sculpey. Since the piece is going to be outside in our unpredictable Wisconsin October weather, I was concerned with the clay holding up (I had planned on coating the hands with at least three coats of Plastidip when I was using the Crayola clay). So I did a quick Google, and found this article!

    Now I’m going to pull all the old clay off, build up the hand shape with foil, and then use Sculpey over it. Thank goodness it’s waterproof!

  5. ¿la arcilla polimerica cruda es porosa o no porosa? ¿y la arcilla polimérica horneada es porosa o no porosa?

    1. You asked: “Is raw polymer clay porous or non-porous? And is the baked polymer clay porous or non-porous?”
      My answer: Raw polymer clay is a putty and is actually a mixture, like cookie dough, therefore it is not “porous”. It becomes a solid vinyl mass after baking. It is not porous in the same way that a piece of paper is. It can, however, be somewhat absorbent, depending on the brand. Some brands contain moisture-holding fillers such as chalk or earth clays. They can hold onto water, paint, or varnish more than a non-porous surface like glass. In addition, some brands are can have very small pits in the surface that allow paint or varnish to adhere well.
      Mi respuesta en español: La arcilla polimérica en bruto es una masilla y en realidad es una mezcla, como la masa para galletas, por lo tanto no es “porosa”. Se convierte en una masa sólida de vinilo después de la cocción. No es poroso del mismo modo que un pedazo de papel. Sin embargo, puede ser algo absorbente, dependiendo de la marca. Algunas marcas contienen rellenos que retienen la humedad, como tizas o arcillas. Pueden sostener agua, pintura o barnizar más que una superficie no porosa como el vidrio. Además, algunas marcas pueden tener pozos muy pequeños en la superficie que permiten que la pintura o el barniz se adhieran bien.

  6. Thank you so much for this article! I’ve been tinkering with polymer clay for a couple of years. I prefer to use Super Sculpey and paint my sculptures with acrylics after they’re baked. Unfortunately, I made the mistake of using Mod Podge to seal my paint on many of my sculptures. Elsewhere, I was able to find advice on how to remove Mod Podge, though it takes the paint with it. This article helped me find better sealers. Because of this article, I bought Varathane and DuraClear Ultra Matte, and I absolutely love both of them!

  7. Amazing how this one article clarified sooo many of my noob, beginner questions so that I no longer have any logical reason for procrastinating. Off to open the clay packages and indulge creatively. Thank you.

  8. Thank you very much. I’m going to try Sculpy Firm. i’m not planning to put the plastic container in the oven. I’ll surround it first with two layers of card so it can be removed before curing. At least that is my (evil) plot. Will start on Saturday. BTW, sorry I didn’t get back to you sooner. Had a little computer glitch.
    Thanks again.

  9. I’m making an urn to be placed in a niche by putting polymer clay over the temporary plastic container. What type of clay would you suggest, and what kind of acrylic paints? This is an amazing article. Thank you very much.

    1. I always suggest any of the stronger brands of polymer clay such as Premo, Fimo, Souffle, or Kato Polyclay. You can learn more about the various clay brands here. Be careful about the temporary plastic container…will it hold its shape in the oven while the clay is curing? As for acrylic paints, it depends on the type of effect that you’re going for. Craft paints, such as Ceramcoat are very good and offer more coverage, but for layered, glaze-like, and antiquing effects then artist’s acrylic paints in the tube usually work best.

  10. I went and bought Translucent Liquid Sculpey as per your recommendation to seal my (Sculpey) clay pieces that have been painted with acrylics, however when baked the acrylic paint becomes darker (not burnt) in certain colours. What am I doing wrong for Liquid Sculpey to cause discolouration?
    Cheers

    1. It sounds like the acrylics you’re using have a large amount of chalk filler and are becoming “wet” from the liquid polymer clay. You’re not doing anything “wrong”. But you might want to use higher quality acrylics for your particular technique.

      1. Is there any other way you could suggest that would result in successfully protecting/glazing my existing pieces with the lower quality acrylics?
        Thanks for your reply

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