Sculpey Clay Softener is used to expedite conditioning of firmer clays. When you use it, you are adding a non-phthalate plasticizer back into the clay, which makes it softer. Under ordinary circumstances, our clays do not need additional clay softener. If the clay has been stored in less than ideal conditions, and has become somewhat dry, clay softener can help. You might find you need more or less depending on the condition of the clay. Please note that Clay Softener will not restore clay once it has become very hard or after it has been baked. If your clay is just a little dry or firm, it may only require the addition of Sculpey Clay Softener to reconstitute it (about 6 - 8 drops per 4 oz clay or 2 - 4 drops per 2 oz clay). However, if it is already crumbly, it has either had too much exposure to heat or old enough to have already undergone some chemical changes. At this stage, it cannot be reconstituted satisfactorily.