CLAY: Oil VS Water Based

I've a preference for oil-based clay, since it suits my technical needs the most.
Still, water based clay is unbeatable for certain tasks.
Ideally, one would be equipped and have a studio setup to use both clays, but when a choice must be made for one of the two, having the following information is certainly helpful!

18 inch tall WED clay head. VERY SMOOTH.
My design (drawing), main sculpture by Jean-Pierre Busque, detailing and refining by me.

Waterbased Clay can be sculpted FAST, and smoothed even faster.
With water and sponges and brushes. No toxic solvent, no flame required.
It can be re-smoothed later, when it has become firmer. It can be made flawlessly smooth.
My favorite is Earthenware. It's amazing!  It's alive, it's MAGICAL!
Except it has its drawbacks. MAJOR drawbacks for some.
It dries, therefore it can crack, it can fall off the armature, and work has to be redone.
This can be prevented of course, by spraying water as one works (not too much!), and by keeping the sculpture protected by moist towels covered with a plastic bag, until the next work session.
Wash and replace towels every few days.
Waterbased Clay dries our hands as we work with it. Use a good hand cream after every hand washing, and take breaks occasionally.
It produces dust. A lot of dust. The mess goes everywhere as you walk away from your work station.
And, you are breathing it in. Silica is not something you want in your lungs. I got sick from it when I was in College, because I was sculpting in my bedroom. NOT a good idea with dusty materials.
Waterbased clay becomes harder and firmer as it dries, which is a necessity if you want to fire it in a kiln and get a ceramic sculpture.  But this same property becomes the enemy of the worker of fine, thin details.  Small fingers for example, will dry faster than the rest of the sculpture, and provoke a lot of frustration. When you need to sculpt an action figure or a puppet with moving parts to be reproduced later by the use of molds, waterbased clay is not the usual choice.
You can re-use this kind of clay if you keep it clean and moist, but protect it from contamination by products and dust, to prevent mold from forming in it. For long term storage, let it dry, and store in a container. Re-moisten in a large bucket, DAYS before you plan on re-using it.
My favorite type of waterbased clay: WED clay. It dries a bit slower than other clays, thanks to its glycerin content. I don't have any at the moment, as it is not available in a local store, but I plan on getting some again someday. In the meantime, a locally-made earthenware does what I need, which these days is making clay walls for making molds over my oil-based clay models. Because oil repels water, the two clays don't merge, and keeps my sculpt clean during the process.


Oil-Based Clay, aka Plasticene or Plastalina, takes a long time to smooth, but that's the only major disadvantage I can find about it.
A good quality Plastalina is firm at room temperature, and can be left on a shelf for YEARS without damage to it, as long as it suffers no physical attack. Cover to protect from dust, keep way from heat sources and the sunlight, and that's it. No drying, no cracking, as long as it's not on a porous surface or armature.

Because it is both firm and relatively pliable at room temperature, it can be used in very thin applications, without cracking. The firmer plastalinas can be used to make a sculpture in multiple parts, with articulations worked into the model.  This is especially useful for making action figures and even static sculptures meant to be molded in a more practical approach, for easier reproduction and assembly.  Smoothing can be done easily with solvents, but those are toxic and I avoid them whenever possible. My current "solvent" of choice is rubbing alcohol (70%), with a small amount of mineral oil, to prevent the formation of dust when rubbing the sculpture. It's not perfect as a smoothing method, it takes a lot of time and repetition. For the rare times i needa really smooth finish, I'll use a strong solvent, and apply it outdoors.
A tool I cannot sculpt oil-based clay without is the alcohol torch, by Buffalo. And despite some instructions warning us to use only 100% ethyl alcohol, I've always used Methyl Hydrate with success. It is easily found in hardware stores, and is much more affordable.
Because of its wax content, this type of clay can be made temporarily firmer by freezing it. It will retain the cold for a while, and the harder surface can be smoothed and detailed with further fine control. I sue this to detail eyelids and final textures.  My favorite clay these days: Monster Clay , by Monster Makers. It melts easily in the microwave oven and in the crock pot, it shapes wonderfully well, and is not tacky against fingers or tools. The smell is faint and pleasant, and the light brown color reveals details easily, and looks good on photographs.
The clays I used and liked previously: Chavant NSP Soft(tan color), and Prima Plastalina.

An old model made from Monster Clay, melting in a crock pot.

In short:
Waterbased Clay
Advantages: Sculpts fast, smooths fast and perfectly, is reusable, can be fired as a permanent ceramic sculpture.
Disadvantages: messy, dusty, dries and cracks.


Oil-based Clay
Advantages: sculpts relatively fast, does not dry, firm and stable at comfortable room temperature, can be worked in a harder state if frozen, is reusable. Disadvantages: takes more time and effort to smooth, and requires a mold to be made to make a reproduction as a permanent sculpture.

Monster Clay sculpt, with wood eyes and teeth. Teeth will be removed for mold making step.