Testing Polymer Clay Sealers

40 sealers, 5 clay brands, learn which polymer clay sealers made the grade, and which ones failed.No polymer clay group or forum seems to escape the inevitable questions about using polymer clay sealers, varnishes, and glazes. Which ones are “clay safe”? Which ones turn sticky or get cloudy or peel off? Why are there so many opinions? Do you even need to use a sealer at all? (No, you don’t.) There are so many questions and no solid answers. But really, unless you test these products, it’s impossible to know which are the best polymer clay sealers. So that’s exactly what I did. (By the way, I’m using the terms sealer and varnish interchangeably…I found no difference.)

Over the past two years, I have gathered all the polymer clay sealers, varnishes, glazes, and dimensional glazes that I could find. I even brought some varnishes from the UK so I could find a Varathane alternative for British clayers. I applied these products to five different brands of polymer clay and evaluated their performance over five months. The results are not what I had expected. Frankly, most varnishes failed on at least one brand of clay, and there were only a small handful that performed well on all five brands of clay. Varathane still scores well, but some of the others I’ve recommended in the past, do not. (Yes, I have now changed those articles!)

Summary of Sealer Tests

  1. Each polymer clay sealer behaves differently on different brands of clay. The same varnish would be great on one brand of clay and fail miserably on another. Choose the right polymer clay sealer for your brand of clay.
  2. Nearly all varnishes, glazes, and sealers were unsuitable on at least one brand of clay.
  3. You don’t need to use a sealer in many cases, but if you do use one, choose PYM II, Varathane, Pearl Ex Varnish, or Cernit MATTE varnish for maximum compatibility with all clay brands.
  4. You may get better performance by matching the sealer to the brand of clay, and not looking for one that works on all.
  5. Consider using liquid clay when sealing surface treatments on polymer clay.

Testing Polymer Clay Sealers

This was a big job, and so this article will have a lot of information in it. Grab a cup of something refreshing and settle in for some reading. Based on my spray sealer tests, I knew that different brands of clay would react differently. I chose Sculpey III, Kato Polyclay, Premo, and Fimo Professional. Syndee Holt asked me to test Souffle as well, and I was happy to add it in. I wanted to test for both cloudiness and yellowing, so I needed both black and white clay. I added colored clay as an extra test. Here’s how I set it up.

Test tiles were made from five brands of clay to use as the base for testing polymer clay sealers.
Here are the test tiles that were used to evaluate the polymer clay sealers. Included were Sculpey III, Kato Polyclay, Premo, Fimo Professional, and Souffle.

How Sealers Were Tested

Master Cane

I made a master cane with each brand of clay using black, white, and primary colored clay. These canes were about 4 lbs (1800g) each. You can see how I reduced these canes using square dowels here. I then used my LC Slicer to make slices from each cane. Each slice became a test tile. I baked all tiles at their proper temperatures according to their label directions. Each tile was wiped with alcohol to remove any oils that were on the surface. Finally, the tiles were labelled on the back with a paint marker. Here’s the Kato master cane.

Varnish Application

Each varnish was first stirred with new wooden stir-stick. I applied three coats to the tile with a soft brush using identical stroke patterns on each tile. The surface was allowed to dry to the touch between coats (typically 30 minutes or so). I did not heat set the tiles by baking them after the varnish dried.

Storage of Tiles

The tiles were stored flat in the open air, on a rack, in my studio for five months. My studio is exposed to normal household temperature conditions with an open studio window at times. Both temperature and humidity changed greatly as the season changed from summer through autumn into winter. They were evaluated at 1 week, 1 month, and five months.

Brush strokes are a problem with many polymer clay sealers.
Here’s an example of brush strokes on a tile made from Fimo Professional. The tile on the left is bare, the tile on the right has three coats with Sculpey Satin Glaze.
This spray varnish didn't spray evenly and was easily scratched from Souffle polymer clay.
Molotow Spray Varnish didn’t spray evenly on this Souffle tile, and it was easily scratched off.
Some polymer clay sealers get sticky with time.
This Premo tile was coated with Krylon Preserve It!, a sealer intended to protect artwork. As you can see, it was so sticky that the police could use this to take people’s fingerprints!
Many polymer clay sealers contract or shrink over time, causing the clay itself to curl.
Many polymer clay sealers shrink or contract over time, causing thin pieces of polymer clay to curl.

Evaluation of Sealers

I evaluated the sealer itself for color, clarity, thickness, odor, and drying speed. These features are the same for all clays as they refer to the sealer itself. I evaluated the test tiles (the dried varnish) for gloss level, smoothness, cracking, clouding, yellowing, scratch resistance, peeling, stickiness, and thickness of coating (coverage).

I tested the scratch resistance by using my fingernail to dig at the coating, and to see if it would peel once scratched. By pressing my finger onto the tile and lifting, I tested stickiness. If the tile stuck to my finger at all, it gained a “sticky” rating. I also evaluated the tiles for the “feel” of the varnish and for smoothness issues such as brush strokes or bubbles.

Criteria for a Recommendation

As you can imagine, there was a lot of judgement involved here. I tried to be objective, but how do you really quantify “how much” scratching or how much cloudiness is too much? I would still give a “yes” vote for a sealer with poor performance in one area if it was really good in all the others.

However, if there was any stickiness at all, at any point during the testing period (after the initial drying time), the varnish would receive a “no” vote, even if the tile wasn’t sticky later. I also gave a “no” vote to any sealer that could be easily scratched off with little effort. To get my top pick as “the best”, the product had to work well on all five brands of clay that I tested.

Sealer Results

For detailed results of my polymer clay sealer tests, have a look at this spreadsheet. There you can see exactly how each sealer scored, on each characteristic, on each brand of clay. I would like to give a you a yes/no for each product, but because they acted so differently on the various brands of clay, I can’t do that. Here is a summary of how each product performed.

Sprays

  • I tested more spray coatings on polymer clay, once again PYM II was the only one that worked well.Krylon Preserve-It! Spray – This spray never dried and was extremely sticky and goopy on all brands.
  • Krylon Workable Fixatif Spray –  This spray was very pebbly and did not spray evenly on the surface. Sticky on Premo, Fimo Pro, and Souffle.
  • Molotow Premium Spray – While this spray was only sticky on Fimo Professional, it didn’t spray evenly to make a smooth surface. It was very pebbly.
  • PYM II – As with all my other tests of this spray, it worked beautifully on all brands of clay.

For more spray sealer tests, check out my article that is specifically on that subject.

Matte Varnishes

  • These matte polymer clay sealers were tested for performance on five brands of polymer clay.Cernit Matte Transparent Varnish – One of the very few varnishes that is scratch-resistant on Kato. Makes a lovely dry-feeling and durable varnish on all clay brands tested, but is not really very matte. It’s more of a satin.
  • Swellegant Clear Sealant – Sold by Christi Friesen, this light-bodied sealer is perfect for fixing surface treatments. Sadly, it beads up on Kato, but is nice on the other clay brands.
  • DuraClear Ultra Matte – Very light-bodied dead matte varnish that is scratch resistant on Fimo Pro and Souffle and good for low-wear items made from Sculpey III and Premo. Not suitable for Kato as it can be very easily scratched and peeled off. My new favorite matte varnish!
  • Golden Matte Polymer Varnish with UVLS – A dead matte varnish that is highly recommended in the polymer community. However, it scratches very easily from Sculpey III, Kato, and Premo. It gets sticky on Fimo Professional. It works better on Souffle, but can still be scratched off.
  • Duncan Matte Sealer – Sold by ceramic suppliers, this sealer is sticky on Premo, Fimo Professional, and Souffle and scratches easily from Sculpey III and Kato.
  • Mod Podge Matte – Similar to white glue, this papercrafting stand-by has terrible brush strokes and isn’t very matte. It turns white when in contact with water. There are better choices.
  • Daler-Rowney Soluble Varnish, Matte – Used for varnishing acrylic and oil paintings, I just added this in because I had it on hand. It doesn’t work on any brand of clay that I tried. Sticky and gooey.
  • Liquitex Matte Varnish (red label) – Also used to varnish paintings, this one peels easily from all clays that I tried, and was sticky on Premo, Fimo Professional, and Souffle.
  • Genesis Heat Set Matte Varnish – Not so much a varnish as a version of liquid clay, this mayonnaise-textured gel works great on all brands of clay, chemically. But the texture of your application method will show, whether you sponge or brush. It does not self-level.

Satin or Semi-Gloss Varnishes

  • Satin or semi-gloss polymer clay sealers were tested.Final Coat – Available in low gloss and semi-gloss, this light-bodied sealer works nicely as a fixative for mica powders. Not a heavy duty protectant, but works nicely on all clays except for Kato which either beads up or scratches readily.
  • Liquitex Satin Varnish (red label) – Cloudiness is apparent on dark colors. Peels easily from all clay and gets sticky on Premo and Fimo Pro.
  • Sculpey Satin Glaze – Has obvious brush strokes (esp Fimo Pro) and is cloudy on all clays. Scratch resistant on Kato (which is unusual) and Souffle.
  • Polycrylic Clear Satin – This wood varnish has a vinyl-like or rubbery feel to it, but works nicely on Sculpey III, Fimo Pro, and Souffle. Scratches very easily from Kato and Premo.
  • Varathane Polyurethane Satin – Also a wood varnish, this polymer clay favorite has a dry feel and no stickiness on any brand of clay. Can be scratched off if you dig at it on all brands but Fimo Pro.
  • Future Acrylic Floor Finish – No longer available (replaced by Pledge Floor Care), this light-bodied and completely clear finish is lovely on all brands of clay. Not a true gloss, more of a semi-gloss, but can be glossier with many coats. Smells like apples and pears. Is never sticky. Sadly, this can be scratched off most clays and isn’t terribly durable.
  • Pledge Floor Care Finish – Nearly identical to Future (above) except that it has a different smell and is just a smidge more glossy. Does not get white when in contact with water.

Gloss Varnishes

  • These gloss polymer clay sealers were tested on five polymer clays. Results at The Blue Bottle Tree.Golden Polymer Varnish w/UVLS – This popular varnish peels easily from all clays, beads up on Kato, Fimo, and Souffle, and is sticky on Fimo Professional. I know it’s popular, but it really scored badly here.
  • Media Gloss Varnish – I found this in HobbyCraft in the UK, but it is available in the US as well. It beads up on Kato, Premo, and Fimo Pro, and scratches easily on all but Souffle. On Souffle, however, it is a phenomenal varnish giving a durable high gloss shine. Highly recommended for Souffle only!
  • Cernit Transparent Varnish, Glossy – Beads up on all clays, but it’s so bad on Kato that you cannot get any coverage at all. Cloudy on Kato and Souffle.
  • Duncan Gloss Sealer – Here’s another ceramic sealer that had terrible brush strokes and was sticky on all brands of clay.
  • Sculpey Gloss Glaze – There were obvious brush strokes and distinct cloudiness on all brands of clay. Oddly, I found that by 5 months, this finish crackled on all brands of clay, and was most obvious on Kato.
  • DuraClear Gloss Varnish – This craft store varnish beads up on all brands of clay, but eventually smooths out with several coats. Can be easily scratched off Kato. Has a nice feel on Fimo, but caused the test tile to curl. On Souffle it seemed great until I noticed that it had fine bubbles in the varnish. Few things are good on Fimo, so this is a good one to try.
  • Gloss Medium & Varnish (green label) – This was sticky on all clays tested. Do not use.
  • Liquitex Goss Varnish (red label) – Cloudy on Sculpey III, Premo, and Souffle. Sticky on Fimo. Fine bubbles on Souffle. Beaded up on application on all clays. There are better varnishes.
  • Fimo Gloss Varnish – Beading up and cloudiness are the issues with this varnish. Makes a good varnish for Fimo Professional and Souffle, however.
  • Ronseal Interior Gloss Varnish – This is a UK brand of hardware store polyurethane and it’s truly remarkable and scratch resistant on Sculpey III, Kato, and Premo. But it is sticky on Fimo Pro and Souffle.
  • Wilko Quick Dry Varnish – Another UK varnish, this is lovely on Sculpey III, Premo, and Souffle. It peels from Kato and is sticky on Fimo Professional.
  • Polycrylic Clear Gloss – Available everywhere in the US, this varnish has a vinyl-like feel and isn’t very gloss on any clay. Gives a good finish on all but Kato. It’s satin on Fimo Pro, however, but glossier on Souffle.
  • Varathane Polyurethane Gloss -This much-loved polymer clay sealer is dry and lovely on all brands of clay. It can scratch and peel off if you dig at it, but it’s perfectly durable for all but the most roughly-handled pieces.
  • Mod Podge Gloss-Lustre – This papercrafting glue-based decoupage medium is very glossy but gives terrible brush strokes. Not at all water resistant, this turns brilliant white when it gets wet. Not really a suitable polymer clay sealer or varnish.
  • Darwi Vernis – This alcohol-based varnish from the makers of Cernit gives a lovely thick, glossy coating. But it scratches easily from Kato. It turns white and crackles if flexed. I know I have recommended this in the past, but I have to change that. Sad. I liked the way it looked.
  • Pearl Ex Varnish – There is no mica powder in this, but it is sold by the same company. This satin-sheened varnish has a lovely dry feel and is scratch resistant on all clays. It leaves a slight orange-peel texture on Fimo, but is wonderful on the other brands of clay.

Dimensional Glazes

  • These dimensional glazes were tested on five brands of polymer clay.Aleene’s Jewelry Pendant Gel – A very glossy dimensional glaze that does show scratches and can peel if you pick at it. Nice and smooth on most clays, but is sticky on Fimo Professional.
  • Mod Podge Dimensional Magic – Obvious brush strokes and bubbles make smooth application impossible. Sticky on Premo. Shrinks over time, causing the clay to curl upward. (And this one fared pretty badly on paper in other (unpublished) tests, too.)
  • Diamond Glaze – Dries blotchy with brush strokes and bubbles. Gets sticky on Sculpey III, Premo, and Fimo Pro. Shrinks and causes the clay to curl.
  • Triple Thick – Readers tell me this glaze turns sticky, but I didn’t see it on any brand of clay (so far). All tiles showed blotchy brush strokes. This is the glossiest of all the products I tested. All tiles curled upward. Has a rubbery feel that shows fingerprints, that are highly visible on black.

Best Sealer by Clay Brand

Because there is so much information here, I’ve struggled to present it in a way that makes sense for you. The above info is great if you want to see how a specific polymer clay sealer works, but it’s pretty hard to figure out the best sealer for the brand of clay that you use. To help clarify, here’s a list of products that worked well with each brand of clay. I’ve highlighted my top pick for each clay brand in green (though this is subjective and you might like a different product better).

Sculpey III

These polymer clay sealers tested well on Sculpey III.
These polymer clay sealers and varnishes performed well on Sculpey III.
  • PYM II
  • Sculpey Satin Glaze
  • Polycrylic Clear (satin and gloss)
  • Varathane (satin and gloss)
  • Final Coat (both semi-gloss and low-gloss)
  • Cernit Matte Varnish
  • Swellegant Sealant
  • DuraClear Ultra Matte Varnish
  • Ronseal Interior Gloss Varnish
  • Wilko Quick Dry Varnish
  • Pearl Ex Varnish
  • Genesis Heat Set Matte Varnish

Kato Polyclay

These sealers performed well on Kato Polyclay.
These polymer clay sealers and varnishes performed well on Kato Polyclay. Note how there are fewer, and they tend to be different to those that work with the other clay brands.
  • PYM II
  • Sculpey Satin Glaze
  • Varathane (satin and gloss)
  • Cernit Matte Varnish
  • Ronseal Interior Gloss Varnish (UK only)
  • Pearl Ex Varnish
  • Aleene’s Jewelry Pendant Gel
  • Genesis Heat Set Matte Varnish

Premo

Polymer clay sealers tested well on Premo polymer clay.
These polymer clay sealers and varnishes performed well on Premo.
  • PYM II
  • Polycrylic (satin and gloss)
  • Varathane (satin)
  • Final Coat (semi-gloss and low-gloss)
  • Cernit Varnish (matte and gloss)
  • Swellegant
  • DuraClear Ultra Matte Varnish
  • Ronseal Interior Gloss Varnish (UK only)
  • Wilko Quick Dry Varnish
  • Pearl Ex Varnish
  • Aleene’s Jewelry Pendant Gel
  • Genesis Heat Set Matte Varnish

Fimo Professional

These polymer clay sealers and varnishes performed well on Fimo Professional in my tests. Read more at The Blue Bottle Tree.
These polymer clay sealers and varnishes performed well on Fimo Professional.
  • PYM II
  • Polycrylic (satin and gloss)
  • Varathane (satin and gloss)
  • Final Coat (semi-gloss and low-gloss)
  • Cernit Varnish (matte and gloss)
  • DuraClear Ultra Matte (and gloss)
  • Fimo Gloss
  • Pearl Ex Varnish
  • Genesis Heat Set Matte Varnish

Souffle

These varnishes and polymer clay sealers tested well on Souffle.
These polymer clay sealers and varnishes performed well on Souffle.
  • PYM II
  • Sculpey Satin Glaze
  • Polycrylic (satin and gloss)
  • Varathane (satin and gloss)
  • Final Coat (semi-gloss and low-gloss)
  • Cernit Varnish (matte and gloss)
  • Swellegant
  • DuraClear Ultra Matte
  • Golden Polymer Varnish with UVLS (matte)
  • Media Gloss Varnish
  • Fimo Gloss
  • Wilko Quick Dry Varnish
  • Pearl Ex Varnish
  • Aleene’s Jewelry Pendant Gel
  • Genesis Heat Set Matte Varnish

Um…I had different results!!!

Did your favorite coating receive a poor score? Have you had bad results with a polymer clay sealer that I’ve recommended? This is not surprising. Varnishes, sealers, and polymer clay formulas are constantly being tweaked by the manufacturers. I can only vouch for the clay that I have and the bottles and jars of product that I tested. There are SO many variables and even things such as contamination by brushes can change the results. Even a different manufacturing lot can perform differently. Undercured polymer clay can also result in sticky paints, sealers, and varnishes. Make sure you’re baking your clay properly.

Because of this variability, you should always test any polymer clay sealers and varnishes that you use with your clay. This is even true if you’ve successfully used a polymer clay sealer with a different brand of clay, and especially relevant when working on an important project.

Another factor that comes into play is paints. When you apply a varnish over a paint, the potential increases for chemical interactions. Many paints remain sticky on polymer clay, too, and adding a varnish over that can give highly unpredictable results.

Phyllis Cahill ran a series of tests evaluating how well sealers adhered to various brands of clay and surface treatments such as metal leaf and Perfect Pearls. Her results differed from mine to a degree, which underscores the variability we seem to get when working with polymer clay sealers and varnishes.

Tip: If you have piece that’s sticky from incompatible paints or polymer clay sealers, you can often cover the stickiness by giving it a coat of Varathane.

Recommendation for Polymer Clay Sealers

So bottom line, what is my top pick for which sealer I recommend? It’s really hard to say because it depends on what effect you want. Few of these sealers are identical. Some are thick and glossy, some are thin and matte. There are no quick and easy answers. Here are some key points.

  • PYM II is the only spray that I recommend. All others are either sticky or have a poor finish.
  • Varathane is an excellent all-purpose varnish that shows no signs of being sticky on any brand of clay. If you use many brands of clay and only want to invest in one polymer clay sealer, this is probably the best bet. It is not, however, the best-performing varnish on any one brand.
  • Pearl Ex Varnish performed well on all brands of clay, a bit less so on Fimo Pro. Certainly a good varnish to use.
  • Cernit Matte Varnish is another stand-out, but it’s not very matte. It’s more like a satin.
  • DuraClear Ultra Matte Varnish by Americana gives a luscious dead matte finish on all clays except for Kato.
  • Final Coat and Swellegant are both super light bodied sealers that are a great alternative to PYM II when you need to seal mica powders. They go on quickly without much brushing, and dry in no time.
  • Varathane is now available in the UK from Amazon. But if you go to Homebase, you can get Ronseal Interior Gloss Varnish that performs beautifully on all but Fimo and Souffle.

Changing Recommendations

Don’t ever say I won’t admit when I’m wrong. Sadly, I have given bad advice in the past! Previously, I’ve recommended Golden Polymer Varnish and Liquitex Varnish. I did use both varnishes in practice, and they did work for me. But that was before I tried those varnishes on multiple clay brands. Because these products performed poorly in these tests, I no longer recommend them and have changed the relevant articles. My apologies if I led you astray. I was going on the information that I had at the time. I know more now. 🙂

Polymer Clay Sealers – Only If you Have To!

As you, hopefully, can see, there is no one sealer or varnish that works beautifully and perfectly in all situations and on all brands of clay. It’s important to note, polymer clay sealers add an element of complexity and bring in the chance for brush strokes, peeling, stickiness, and cloudiness. Please know that polymer clay does not need to be sealed. It’s a durable plastic (vinyl) and the only thing that needs to be sealed is surface treatments that you put ON the clay.

You can use polymer clay sealers and varnishes to change the gloss level of your work, but if what you’re looking for is a super smooth and glass-like finish, the smoothest and most durable solution is to sand and buff your clay. Not sure how to do that? I wrote a 120 page eBook that covers this very subject, in depth! Click here to learn more about the Sanding and Buffing (and Finishing) eBook!

Alternatives to using Polymer Clay Sealers?

As I just said, the best way to get a smooth, glass-like finish is to sand and buff your project. Knowing how to do this quickly and easily (and without painful fingertips) is a valuable skill to add to your repertoire. Get the 120 page eBook here!

Another solution is to use liquid polymer clay as a clear coat and fixative. Translucent Liquid Sculpey makes an excellent matte fixative. Just use a cosmetic sponge to (very) lightly dab it onto the surface of your project, then bake again. Yes, this can be done over paint and other surface treatments.

Liquid Kato Polyclay can be used to make a super-smooth and glossy finish and sealer on your clay projects. There is a bit of a learning curve, but when done using a heat gun, liquid Kato makes a hard, non-rubbery, durable and chemically compatible finish on your clay. To learn more about that, I highly recommend getting Debbie Crothers’ video tutorial Curing Liquid Kato Clay. She takes away all the mystery of learning this essential skill.

Alternatively, resin (both epoxy resin and UV resin) is also a good method for coating polymer clay. But I didn’t test resins in this article…that’s for another day.

Acknowledgements

In conclusion, there are some people I want to thank. Although I did buy most of the clay and sealers used in this article, I was thrilled to receive some of the products to help me with the cost a bit. Many thanks to the following people:

Iris Weiss of Polyform (the Sculpey people) sent me a huge package of Souffle in just the colors I needed to make the 4 lb cane I used for the Souffle test tiles.

Bottles of Final Coat were provided by Wendy Orlowski of Shades of Clay. This was one of the first sealers I collected, so it’s been a while. Thank you for your patience, Wendy! Shades of Clay is a great Canadian polymer clay resource!

Cernit Varnishes, both Matte and Gloss, were provided by Marina Taenkova of Marka Decor Premium. Marina carries the full line of Cernit clays in the US.

I wanted to include Christi Friesen’s Swellegant sealant in these tests, and Lisa Lambright of The Great Create happily sent me some to test.

And if sealers aren’t your thing, learn more about the art of sanding and buffing…

Learn all about getting the best finish on polymer clay with this 120 page Sanding and Buffing Polymer Clay eBook.

Click to learn more….

 

 

 

 

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