Strongest Polymer Clay (not a simple topic!)

Nobody wants to spend time working on a project only to have it break when handled, worn, or used. We want our polymer clay creations to be strong and durable! So what’s the strongest polymer clay brand?

Well, that’s kind of a loaded question. You see, “strong” can mean many things. Does it mean more flexible? Or more rigid? Does the strongest polymer clay stretch like elastic? Does it bend easily, or is it stiff and does it resist deformation? Will strong polymer clay resist cracking? Or is it harder and more like stone or granite? Does it hold up under pressure and compression? What about shear and twisting? Brittleness? There are many types of strength, as you can see. So how can we determine the strongest brand of polymer clay?

graphic that says strongest polymer clay brand and shows hands twisting a piece of polymer clay.

Baking Is Important

Polymer clay is vinyl, so it will always be flexible and will never be hard as stone. Each brand of polymer clay has its own feel and performance, both before and after baking/curing. They are not all the same.

That being said, the most important factor in the strength of your polymer clay project is proper baking. Baking polymer clay is not an all-or-nothing process. It’s a continuum. And generally, the longer something is baked, the stronger it is. All brands will be brittle when they are underbaked. If you’re unsure what that looks like, check out my article here. And if you’re struggling with baking strong pieces without color change, you may want to save time and get this tutorial.

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Strongest Polymer Clay Brands

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Before I go further, I do want to mention that some brands of polymer clay are always brittle and should only be used at thicknesses greater than 1/4″ (6mm) thick or used for projects that won’t be handled. These brands include Sculpey Original, Sculpey III, and Super Sculpey (Affiliate Links – learn more here).

Flexible Brands of Polymer Clay

While no brand of polymer clay can stretch like bubble gum or a rubber band, most have at least some degree of flexibility. But there is a difference between being able to flex without breaking and the concept of stiffness. Nearly all brands of clay can be flexed without breaking. If you need a strong polymer clay that won’t break when flexed, the most important factor is proper baking, not the choice of brand.

If you need a strong polymer clay that won’t break when flexed, the most important factor is proper baking, not the choice of brand.

These polymer clay brands, when properly baked, will flex without breaking include Cernit, Fimo Professional, Fimo Soft, Sculpey Souffle, Hobby Lobby Craft, Hobby Lobby Advanced, Papa’s Clay, Prism and Pro, CosClay, Sculpey Premo (Affiliate Link – learn more here), and Sculpey UltraLight (Affiliate Link – learn more here). Again, I can’t overstate the importance of thorough baking when creating strong polymer clay projects.

Left hand holding thin strips of polymer clay in red, pink, yellow, orange, hot pink, green, and blue. A beige strip is being flexed between both hands on a white background.

Repeated Flexion

While all strong brands of polymer clay will flex without breaking, not all of them can tolerate repeated flexion. If you bend the clay back and forth repeatedly, “fatigue marks” form as the plastic breaks down and tears. Sculpey Premo will readily tear if you flex it repeatedly. Some clays will get white marks when you do this, especially Fimo and Hobby Lobby clays and Papa’s Clay. If you want clay that can be repeatedly flexed without tearing, CosClay is my number one pick. Prism and Pro is a “no-name” brand exclusively available on AliExpress, but it does seem to have good quality and is quite strong and flexible. Definitely worth a try.

Least Stiff Polymer Clay

On the other hand, sometimes people are actually looking for clay that is less stiff (more floppy). If you are making a journal cover, for example, you might want spiky bits not to feel so hard and pokey. What brands are less stiff and give less resistance when you bend them? The winner here, hands down, is CosClay. It is absolutely the least stiff polymer clay brand. It flexes easily and makes really wonderful tactile bits for your creations. It also makes great toys and figurines. Try encasing wire to make a poseable figure, in fact!

Other brands that are less stiff and more flexible are Sculpey’s Bake Shop Bendy (Affiliate Link – learn more here) formerly called Bake and Bend, Prism and Pro, and perhaps some generic no-name clays from Amazon and other marketplaces.

A strip of beige polymer clay is being flexed between two fingers on a white background.

Stiffest Polymer Clay

If you need clay that is resistant to flexion, is stiff, and bakes harder than other brands, the strongest polymer clay brand for this feature is Kato Polyclay. Baked Kato, while not as strong as stone, is certainly the most rigid and stiffest polymer clay brand after baking.

Strongest Polymer Clay Before Baking

In discussions, especially online, it can often be unclear whether we are talking about baked or unbaked polymer clay. The info above all refers to baked polymer clay. But what about unbaked, raw polymer clay? How does strength come into play here?

If your unbaked polymer clay is too soft, squishy, and easily mashed then have a look at this article to see how important it is to adjust your clay’s consistency. Be aware that the hardness or softness of raw polymer clay is also temperature-dependent. Warm it up, and it becomes softer. Cool it down, and it becomes stiffer.

But even so, there are differences in the way that different brands of polymer clay handle. If you are sculpting, especially when hand-building, the strength of the raw clay mass does come into play. (I wouldn’t normally connect this to polymer clay strength, but Google might have brought you here looking for this info.) When making vessels, you want your unbaked clay to have enough body to support itself without collapsing easily as you make them. Be aware that larger sculptures will need armatures to act as internal supports. You can’t rely on the clay to self-support past a certain size.

The unbaked polymer clays with the stiffest consistency and most body when hand-building are Kato Polyclay and Pardo Professional Art Clay.

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