Most of my sculptures are made using a combination of clays, depending on the task at hand. Apoxie often holds everything together to create a nice strong foundation.
Aves Apoxie Sculpt is an air-dry, 2-part epoxy clay. It dries very hard within 24 hours depending on the thickness. The consistency is clay-like, but it does droop a bit and so must be put over an armature or left to stiffen in order to hold certain shapes.
Mixing equal part from each container is what makes Apoxie Sculpt
It is is very useful product, but I use it only for certain applications; Whenever I know part of the armature will be under strain, when I need things to hold together really well, and sometimes when I have to work really thin and want to ensure that a fragile piece won't break.
Some artists construct entire sculptures from epoxy clays or related clays. Those sculptures are very strong in the end, however; I have found that I do not like to use it extensively for the following reasons:
Potential health effects - It has an epoxy base (read: full of chemicals). It is listed as safe, but it is recommended to mix it with gloves on. The long term exposure to such clays has not really been studied. The other air dry clays I use, like Creative Paperclay, are non-toxic.
Putty-like feel - The texture of this clay is sticky and coats your fingers. The high quality air dry clays that I use are water-based, and feel like ceramic.
Working time - Because the clay hardens based on a chemical reaction, there is no way to slow the drying time. This means that you have about 2-4 hours (depending on the brand) before it starts to harden.
Weight - While dried epoxy clay is rock-hard, it is also quite heavy. If I were to contruct a large sculpture with epoxy clay it would likely be too heavy for a single person to move about.
Semi-gloss finish - When dry, Apoxie Sculpt has a semi-gloss finish that I find it doesn’t take paints and primers as well as lightweight clays. I find this is similar to polymer clays because the dried product is essentially a plastic as opposed to a clay body.
Despite all of these downsides I find it indispensable when constructing strong armatures, and will continue to use it for its strength.
Apoxie Sculpt in action strengthening wire armatures
Are you eager to try some Apoxie Sculpt? These are two potential resources in North America that I know of. Since I’m in Canada, I use Sculpture Supply so I avoid having to deal with any sorts of customs bothers. The main Aves site also has a store locator as well, so you lucky ducks in the US can pop into a retail place and buy it off the shelves.
Other epoxy clay options
There are many other options for epoxy 2-part sculpting clay. I've started using Milliput because I can easily buy it at my local art store. Often local options can be better because you don't have to pay for shipping.
So get out there and be creative! :)