Hi Newby, I think if it's soft... it's good. why don't you try making a few simple pieces, bake them, and see how they hold up. The only time I ever had a problem was when the old clay was hard. It didn't soften with kneading like it usually does. I put it through a pasta maker over and over again but it never became pliable enough to work with. What are you going to make?

Please check out Polymer Clay Central. I have seen in there where people will put old clay in a sock and bash it to make it workable. I know from experience that you can get conditioners that soften up the hard stuff but it takes time a and work to get is pliable. Good luck

Here is a link that might be useful: Polymer Clay Central