When you want to make a sculpture you will have to make a very important choice before even starting on your sculpture and that is choosing your type of clay. The two most often used types of clay amongst hobby crafters are air-dry clay and polymer clay. But which one should you choose and what are the differences between them?
As a whole, the main difference between air dry clay and polymer clay is that polymer clay is a type of thermoplastic that hardens once it is baked in a regular oven. Air-dry clay is a clay and glue mixture that air dries. Polymer clay is more durable and water-resistant while air dry clay is cheaper.
These are only the main differences between air dry clay and polymer clay. If you want to know more about the differences between them and how to choose the right type of clay for your project then read on!
Main Differences Between Air Dry Clay and Polymer Clay
I already mentioned the main differences between air dry clay and polymer clay above but I will go more into detail here and I will also list the advantages and disadvantages of using each of these clays.
Polymer Clay is More Durable Than Air Dry Clay
Polymer clay is made out of plastic and once it is hardened in an oven it is really hard and durable. It can´t be broken easily and it can support a surprising amount of weight as well.
Polymer clay has the reputation of being brittle after baking but that is only the case if it has been baked wrong or if you try to bend it right after it came out of the oven. You can read all about properly baking the polymer clay in another of my articles if you want to know more.
Air-dry clay on the other hand has to be sealed in order to make it more durable. It is still very durable but air dry clay is still not nearly as strong as polymer clay.
I wrote an entire article explaining how durable air-dry clay really is and how to make it more durable if you want to read more about that.
Ultimately, the difference between the durability of air-dry clay and polymer clay is really only important if you want to create a very intricate sculpture or if your sculpture has to support a lot of weight.
Polymer Clay Only Hardens in the Oven
Air-dry clay will start to dry as soon as you take it out of its package. It will take around 72 hours for air dry clay to fully harden and once it has hardened it can not be worked with again but it will soften up slightly when it gets in contact with water.
Polymer clay, on the other hand, has to be hardened in an oven. You can leave polymer clay out for several years and it will still be workable. It only hardens once you bake it in an oven.
You can use your own kitchen oven for baking polymer clay which makes it an ideal choice for a lot of hobby crafters as no kiln is required.
Polymer clay can not be worked with again once it has fully hardened. Not even water, oil, or heat will make it malleable again.
Polymer Clay is Water-Resistant While Air Dry Clay Has to be Sealed
Polymer clay will be water-resistant and very durable as soon as it hardens while air dry clay has to be sealed in order to be durable.
While it isn´t hard to seal air-dry clay, as you can read in my sealing air-dry clay guide, it is still another step that you should do after hardening the clay.
This is why a lot of sculptures prefer using polymer clay. You simply bake it and it will be durable enough to survive the elements and maybe even a few falls from the table.
Air-Dry Clay is Cheaper Than Polymer Clay
The biggest reason to use air-dry clay for most people is the price of polymer clay. 1lb block of polymer clay will cost you around 20$ while the same amount of air-dry clay will only cost you around 10$.
So polymer clay is almost twice as expensive as air-dry clay. This is also the main reason why I still see so many people using air-dry clay instead of polymer clay even though polymer clay is much more convenient to use in most cases.
Air-Dry Clay is Easer to Paint
One of the biggest disadvantages of using polymer clay is that it is a bit annoying to paint. You can use acrylic paint, oil paint, or enamel paint to paint polymer clay but especially water-based paint will need a primer to adhere properly to it. You can read more about painting polymer clay in another article of mine.
Air-dry clay is pretty easy to paint. You can use water-based as well as oil-based paint to paint air-dry clay without needing to prime the surface first. You read my guide on painting air-dry clay if you want to know more.
In the end, you should seal the paint in order to ensure its longevity regardless if you painted air-dry clay or polymer clay.
Polymer Clay Doesn´t Shrink as Much as Air-Dry Clay
When air-dry clay dries water evaporates and that will make the sculpture shrink very slightly. Especially cheap air-dry clay is very prone to shrinking.
Normally that isn´t a big deal. The amount that the clay is shrinking is very little so it will rarly really make a difference.
Polymer clay will shrink as well but only by a very very small amount. So in the end it really doesn´t matter at all unless you need to make a very precisely sized sculpture.
Air-Dry Clay Cracks Easier When it Dries
The biggest drawback to using air-dry clay is that it tends to crack easily if you dry it the wrong way. I wrote an entire article on how to avoid cracks in your air-dry clay.
Luckily you can always fix cracks in air dry clay so, in the end, it isn´t that much of an issue if you know how to avoid and fix cracks in your air-dry clay.
But still, polymer clay will not crack as easily as air-dry clay.
Is Polymer Clay or Air Dry Clay Easier to Use
You may be asking yourself which clay is easier to use. Polymer clay certainly has a lot going for it but it is also a little bit more difficult to harden it while air-dry clay seems to be less durable.
As a whole, polymer clay is easier to use for sculpting because it doesn´t dry up and you can take as much time as you need to finish your sculpture. Polymer clay has to be baked though, which makes the hardening process a little more difficult.
In the end, I would recommend using polymer clay if you want to learn how to sculpt because you are not on a timer and you can take as much time to finish your sculpture as you need without worrying about the clay drying up while you work on it.
If you are new to using polymer clay then you might have some initial difficulties making the clay malleable because it is quite stiff right out of the box. But don’t worry, you can simply use a roller or some mineral oil to make the clay malleable.
Once the clay is soft, however, the whole process is quite straightforward. You can read more about making polymer clay soft in another article on mine where I explain several ways to making polymer clay soft in more detail.