I purchased some Fimo polymer clay some years ago and I have now re-found it; it is about 8 years old. Some of the clay is not sealed. Is the clay re-useable as some of it is very crumbly?
If the block of clay and the crumbly bits are pliable, cut everything into tiny pieces then add drops of Kato Polyclay™ clear medium liquid as you knead the pieces back together. If the pieces start to combine, you are on the right track. If not, continue to add the liquid until you form a nice ball of clay. Once combined, work the clay further then condition it.
If the pieces don't combine after a certain point, it would probably be good to consider the clay beyond help.
- Tammy Honaman, Author, Jewelry-Making Expert and Educator