'Regarding the clay used , there are two types . Boyle Air Drying Clay and La Doll - La Poupee La Muneca Natural Stone Clay.'
Hi S., It looks to me that you are using air dry clay rather than the clay commonly called polymer clay (like brands PREMO, Fimo, Kato, Sculpey, etc......though Sculpey is not always recommended). This may be why you are having difficulty with your molds. I know nothing about air dry clay, other than they don't react like polymer clays (commonly called PC) and don't necessary work the same. The reason why I asked what brand of silicone mold you were using was because the maker of the mold might be able to tell you if/how use could be adapted with with air dry. I did find in my archive info on a several tutorials for making babies with PC. I can dig up the URL for you if it's something that interests you.
On a different track, I do know that all molds are not created equal. Various brands have different minerals in them that react with certain polyclays. The silicone molds I make myself work fine with most brands of PC, but using them with Kato brand renders them unable to set up.....so other than the potential problem with using air dry VS PC, I was wondering if you'd purchased other brands of molds and if you had the same problem with all of them.
We're primarily a community of polymer clay enthusiasts here and I don't know of anyone here with much expertise in air dries, but perhaps you'll still get a reply. The other thing I would recommend would be to search for an air dry clay newsgroup, perhaps something on FaceBook.
Hoping you are able to find an answer and if you should ever have a question about PC we'll try to help.
Anita in AZ