I bought some silver Art Clay some years ago, it's never been opened. Do you know if it can still be used? I would be firing it with a butane torch. Thanks!
The clay can still be used. Any unfired clay can be made reusable in one form or the other.
Open the package to see what condition the clay is in. If it is still pliable, squish it a little to see if it softens up to a consistency of soft bubble gum. If so, you are good to go. If not, place the clay into a piece of plastic cling wrap and spritz it or use a finger to apply a small amount of water. Let it stand for a few minutes or until the water is no longer visible. See if the condition has improved; if not, repeat until it has.
If the clay is dried out completely, place it into a top zip bag with a wet paper towel. Let the bag sit for a few days then check the condition of the clay. If necessary, rewet the towel and wait a few more days.
An alternative is to crush the dried block of clay into a fine powder and then add small amounts of water to it until it is the consistency of workable clay. You can use a mortar and pestle for this process; marble is best since it doesn't have grains that would catch the fine particles of clay.