Image: Caulking

Description: Silicone caulking can be used as a basic sealant against water and air penetration. Certain types are also used as a topseal in firestop applications, which are subject to stringent bounding. Oxime based, or "neutral cure" silicones are the best and most expensive, alcohol curing are as effective but have a shorter shelf life, whereas acetic acid (vinegar) silicones occupy the lower price range. Acid cure silicones are able to form adhesive bonds to silica based materials (such as glass), but often fail to adhere well to other surfaces. Neutral cure silicones adhere well to many substrates. Silicone caulking cures by absorbing atmospheric moisture and the escape of certain ingredients, which activate crosslinking. First a "skin" is formed and slowly but surely, the paste turns to solid rubber. Upon combusting, a silica and carbon char is left behind. In firestopping, the thin rubber skin made of any elastomers including silicone minimises smoke transfer and serves to hold back the hose-stream test, which is mandatory in the US and well-liked in Canada - irrelevant most anywhere else.
Title: Caulking
Credit: Own work
Author: Achim Hering
Usage Terms: Creative Commons Attribution 3.0
License: CC BY 3.0
License Link: http://creativecommons.org/licenses/by/3.0
Attribution Required?: Yes