Homemade Polymer Clay* Questions and Answers

Awhile back I posted a recipe for polymer clay. I recently viewed the post and saw all the questions that readers had asked in their comments. Rather than answer each individually, I thought I'd post a follow-up that answers the most frequently asked among them. So, here goes:

Can you add color while the clay is wet?

Yes, you can add acrylic paint or even food coloring, but for even tinting throughout, you'll want to do it while the mixture is still liquid. If you want a swirly effect, then add it to the dough. Be prepared for color-stained fingers. And also note that adding a lot of colorant will alter the recipe and affect how the clay performs.

Does the clay shrink as it dries and how much?

It does, about 15-20%.

Can you bake the clay to speed drying?

Absolutely! I usually dry my items in the oven at about 150°F. How long to keep them in depends on their thickness. Also, if you’re making flat shapes, watch them for curling. Periodically flip them over to keep that to a minimum.

Will dried items stand up to water?

Dried items are water resistant but not waterproof, so if they get a little wet it’s OK, but don’t submerge them in water or even subject them to wet environments. They’ll certainly do better if they’re sealed with polyurethane or acrylic or the like.

Can dried items be used outdoors?

I haven’t tried but wouldn’t risk it. Dried items are water resistant but not waterproof. A sealant will help but I still wouldn’t expect them to last very long, especially in wet conditions.

Can dried items be used for food?

No. While the clay does plasticize during the curing process, it won't stand up to extended exposure to moisture.

Can the clay be used to make shapes with cookie-cutters?

Absolutely! Sprinkle a bit of cornstarch on the surface and roll it out on wax paper, or even in a pasta machine. Flip your shapes over throughout the drying process to keep them flat (they tend to curl).

Can you use glue other than Elmer’s Glue-All?

I haven’t tried but any PVA (polyvinyl acetate) glue should work, with, I would expect, somewhat different but probably OK results.

Cracking?

Shouldn’t be a problem. If it is, your clay might be too dry. Be sure to keep it in an airtight container between uses and only take out what you intend to use immediately.

Stickiness?

Cook the mixture for longer or use a bit less glue. Once out of the pot stickiness is harder to fix but sometimes adding more cornstarch helps. Altitude and likely also humidity will affect how the recipe performs.

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* Not homemade Sculpey or Fimo. The polymer base of those products is polyvinyl chloride (PVC), while for this one it is polyvinyl acetate (PVA). Both PVC and PVA are polymers, and both this clay and commercial polymer clay “plasticize” during a curing process. This clay therefore has many of the characteristic properties of commercial polymer clay (elasticity, pliability, flexibility, durability), but it doesn’t have all of them (particularly insolubility).

Until next time --

Linda Purty Bird

Homemade Polymer Clay

At different points over the last few years I've played around with different kinds of homemade "clay." My favorite is a polymer clay also known as cold porcelain. Its main ingredients are cornstarch and white PVA or Elmer's glue. I like it because it's smooth and a little bit elastic to work with and dries extremely hard. It's also relatively non-porous so it takes paint really well. And it doesn't degrade over time like baker's clay or salt clay does. I've used it to cover blown-out chicken eggs for Christmas ornaments, as well as to make various and sundry bowls, boxes and pendant blanks, among other things.


But it took awhile to get the recipe right. Most of the ones I found online resulted in a compound that was way too sticky to work with. So I experimented with different proportions of glue and cornstarch and the inclusion/exclusion of various secondary ingredients. What follows is the fruit of my experimentation. Lucky you!

Materials
  • 3/4 cup white glue
  • 1 cup cornstarch
  • 2 tablespoons mineral oil (I used baby oil but reportedly even vaseline will work)
  • 1 tablespoon lemon juice
  • Non-stick pot
  • Wooden spoon
Steps
Add cornstarch to glue in a nonstick pot. Mix together and then add mineral oil and lemon juice. Blend well.


Cook over low flame stirring pretty much constantly (you can take a quick break or two if your arm gets tired, which it will) until the mixture resembles mashed potatoes.



Remove from heat! Squirt a little additional mineral oil around the top of your mashed potato mass and with your hands, remove it from the pot. Knead until smooth. It's best to do this while it's still as hot as you can handle.


Pull off a bit to work with and put the rest in a re-sealable plastic bag with the top about half-way open until it's cooled down a bit. Then seal the bag (with as little air in it as you can) and store in the fridge.

Let dry about 2-3 days, then paint, or not.

Until next time --

Enjoy!


Linda
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