Rejuvenating Old Clay Sheets and Veneers

Nancy asked: “How do you “wake up” and soften a slab/veneer you made a few months ago?
I spent more than an hour resuscitating a skinner blend. I thought a few more runs through the pasta machine would fix it. What a mess! Crumbling all over and it softened more or less only on one side.”

That’s a really great question and one that I’ve been meaning to write about fully. Now’s a great time!

Whether we’re saving cool Skinner blends or keeping decorated sheets/veneers for future use, we often run into trouble when it comes time to use those sheets. With time, the sheets usually become brittle, start to crack, and are no longer suitable for being used. What’s causing this and is there a way to save these sheets?

What Causes Brittle Sheets

The cause is simple. Unbaked polymer clay becomes brittle over time because of two factors. One is simply that it ceases being unconditioned and begins to “gel up”. Just like a block of clay that you’ve previously conditioned, if you wait a couple of months it will be hard and crumbly once again. The other factor is that most brands of polymer clay will naturally undergo something called “aging”. Just like leftover spaghetti that gets dry in the fridge and needs more sauce, the PVC particles in unbaked polymer clay continue to absorb plasticizer over time, making the clay mass dry out.

So between “unconditioning” and “aging”, unbaked polymer clay sheets will naturally become much more dry, brittle, and less supple over time.

It’s Not Leaching

While discussions on this topic often suggest that storing sheets in waxed or parchment paper is the culprit, I don’t believe this is a significant issue. Paper does absorb plasticizer, yes. But so does plastic. Yes, that’s right. Plastic also absorbs plasticizer. That’s why the plastic sheets wrinkle and warp. But when the plastic or paper is very thin, it doesn’t absorb very much, making this a minor contribution to the problem, if at all. Aging and “unconditioning” is far more important.

Brand Matters

Just as some polymer clay brands become unconditioned in minutes (or so it seems) and others last forever, the same is true for sheets and veneers. I would expect that Sculpey Original, Fimo, Cernit, Pardo, Papa’s Clay, and CosClay would age quickly. And I’d expect that Premo, Souffle, Sculpey III, and Kato would be usable for longer before becoming brittle.

In addition to brand, be aware that some colors within a brand might have a completely different texture and aging characteristics that other colors within that same brand line. Each color has its own formula! Then there is variation between lots of clay, too. Depends on the variability in raw materials that the factory was able to source over time.

Saving Old Skinner Blend Sheets

Skinner blends are a sheet of graduated colored clay, made with at least two colors of clay. People often like to save them in sheet form in plastic sheet protectors, often having entire notebooks of blended sheets. It’s a great way to get a head start on a project. Because there is just clay in the blend, with no paints or designs on the surface, you can revitalize a Skinner blend by running it through the pasta machine again. It’s not always easy, however.

Don’t be tempted to just fold a blend in half and feed it into the pasta machine just as you did when you made it. Because the clay will be completely unconditioned, it will shatter when the pressure of the pasta machine squeezes the sheets. Start by flexing the full sheet in your hands. Gently flex it back and forth and you should feel the resistance or stiffness of the sheet start to fade. Next, without folding it, feed it through your pasta machine at the thickest setting. Do this a few times. Even if it doesn’t feel like much is happening, it is! Then take it down one step. Gradually thin the sheet down to maybe a #4 or so. THEN, fold the sheet and put it through the pasta machine on the thickest setting.

By doing this gradual process, you’ll avoid “fracturing” the sheet with pressure and will (hopefully) wake it up. You should soon be able to work the sheet as you normally do.

Add Softener Perhaps

As Nancy found, however, sometimes one color has aged more than the other (or maybe both colors have aged) and the clay is too brittle to hold together to make a sheet. In this case, rub some clay softener or liquid clay onto the sheet and let it soak in for a few hours or even days. Then try the gradual process above. You may need to add more softener to one side of the blend than the other, depending on the condition of the clay you have. There will be some judgment involved as to how much to add, but take it slow and see how it goes.

Saving Old Veneer Sheets

On the other hand, saving patterned sheets or surface technique veneers is very challenging because you can’t mix them up to condition the clay. You can’t even roll them very much or you’ll stretch or crack the patterns and designs that you wanted to save. When saving this type of veneer, its helpful to remember that conditioning isn’t about mixing as much as its about disturbing. Your goal here is to disturb the clay base without mixing it.

Try this. First, lay the sheet (in its plastic sleeve) face down on your table. Gently peel the plastic off the back of the clay sheet, taking care that you don’t lift the clay as you go. Take your time. Now flip this over and lay the back of the sheet onto a new piece of cling film or plastic wrap. Now gently peel the front sheet of plastic off, if you can. Now you have released both sides of the sheet from its plastic sleeve and it’s sitting face-up on a piece of plastic wrap.

Next, lay a sheet of non-stick parchment paper over the clay sheet and use an espresso tamper (or similar) to rub the entire surface, applying gentle, yet firm, pressure. The goal here is to apply pressure to the underlying clay, without disturbing the surface pattern.

You should already begin to feel the difference and you will likely notice that the clay sheet can flex without cracking. Keep gently flexing the sheet to further “condition” the clay. If you see cracks, gently press them back together.

Try Clay Softener

As with the Skinner blends above, you might need to apply clay softener to the back of the sheet. Just flip the sheet face down and spread some liquid clay or clay softener onto the back of the veneer. Let sit for a few hours and keep working with the sheet.

A Failure?

Yes, sometimes there’s nothing that can be done and the sheet can’t be saved. This most often happens when you have made the clay sheet quite thin, have used a clay brand that fractures/shatters easily, or have used paints that are, themselves, cracking. In that case, you may still be able to use the pieces. Just apply them to a new base of clay and try to piece them together like a puzzle. Sometimes you can make it work. Good luck!