5. What are Fillers?
Some lower quality silicone coatings contain filler that may be hazardous.
The reason why it’s done is because unfilled silicone elastomers achieve only low mechanical strength when cured and so adequate strength is obtained by incorporating reinforcing mineral fillers. Small-particle-size silicas (same as silicone atomic structure) are used almost exclusively for this purpose. Because of this small particle size elastomers with high transparency can be produced. On the other hand, a slight whitening of the silicone item might occur when squeezing or pinching it.
Although 100% silicone is non-stick, these filling materials may not be. All the time and effort you put into baking the perfect cakes (and indeed the reason you selected silicone in the first place) may be in vein if the baked goods stick to the pan due to these fillers. 100% silicone is heat resistant to over 300°C (well above normal cooking temperatures). It will not give off odours, discolour or compromise its integrity. However the same cannot be said for the filling material. Silicone, in its limited research, is not dangerous to use or to the environment in any way but who knows what other materials have gone into Non-100% silicone products? Particularly if subjected to heat, cooking ingredients, food acids etc.. Be under no illusion that quality silicone will cost more than wooden or metal utensils but should instead be considered an investment that will stand the test of time whether only occasionally used in a domestic kitchen or extensively in professional kitchens.
The filler issue is an important one as the filler could be made of anything. If you’re set on buying silicone cookware, check with the manufacturer regarding this. To test for filler yourself, one suggestion is to twist the item and if white shows up on the bend, the piece likely contains filler. - greenlivingtips.com, mastrad.com.fr, Ezinearticles.com