No real knowledge here,LOL, but i believe i will take a shot at it. Silicone in the tube isnt 100%pure. Like they pump it out of the ground, filter out the impurities and package it up. Right! Naw, its got plenty of additives but stays within some government guidelines to be able to claim pure silicone. However by varying the percentages of the added additives they can change the properties of the product silicone. Make it adhere better or maybe remain softer when cured or even stink less. They try to give it properties they think will make it more attractive to the consumer. Us. So they can sell more and make big profit.LOL I think.