Strips of 5″ X 3/4″ unbaked white Fimo and Cernit polymer clay on graph paper.

I was recently reading The Polymer Arts magazine, which I really enjoy. One article said polymer clay doesn’t shrink.  Another article in the same issue said it does.  I’m sure those are true experiences for each author, but it’s confusing for novices like me.

A few months ago, I made two tissue blade cases using Kato polymer clay.  I cut the clay to perfectly fit around the magnetic sheets I’d cut.  I was surprised that after baking the cases, the magnetic sheets no longer fit.  I had to trim over  1/16″ off the length and a tiny bit off the width to get them to fit again.

Why had I read so often that polymer clay doesn’t shrink when clearly it does?  The answer is simple.  Some brands shrink, some don’t.

The photo above shows unbaked strips of Fimo and Cernit.  The photo below shows the same strips after baking. There’s a tiny bit of shrinkage in the length of Fimo.  You really have to look for it.  I can’t see any shrinkage with Cernit.

The same strips of white Fimo and Cernit after baking and cooling.  The shrinkage in Fimo is barely discernible, maybe 1/32″. Cernit doesn’t seem to have shrunk at all.

Below is Premo before and after baking. (I love before and after photos.) There’s been about 1/16″ shrinkage in the length.

Unbaked 5″ X 3/4″ strips of white Premo polymer clay on graph paper.


The same strips of Premo after baking and cooling.  There’s been 1/16″ shrinkage in length.

I also tested Kato and Soufflé.  Kato shrunk about 1/16″ in length. It’s difficult to see any shrinkage in Soufflé.

Unbaked 5″ X 3/4″ strips of white Soufflé and Kato polymer clays on graph paper.
The same strips of Soufflé and Kato after baking and cooling.  It’s difficult to see any shrinkage with Soufflé.  Kato shrunk about 1/16″ in length.

So, now I know.  Premo and Kato shrink a little.  Fimo shrinks a tiny bit.  Soufflé and Cernit don’t seem to shrink at all.

Most polymer clay projects are small, so it may not matter if a 5″ piece of clay shrinks 1/16″.  It depends upon what you’re making. I’ve had seams come partially open because of shrinkage.

I’ll keep shrinkage in mind if I’m making a large piece where precision is important, or if pieces baked separately need to fit well together.  It’s good to know that depending upon the brand, polymer clay does shrink.

The five brands baked.