I think silicone goes off completely all the way through but mastic gets just a skin on top of it and the inner stays 'wet' for years.
I cut my teeth on a product called Secomastic.....oil based, would skin over but took years to fully cure. Yellow / brown in colour it would never come out of the tube in winter.
Forerunner to silicone!
John
Forerunner to silicone!
John
To be strictly accurate, it is resin or sap from the Mastic tree, or bush, originally found in ancient Greece. This resin was used as chewing gum, and there are references to it in various ancient writings, also as a medication to freshen the breath or reduce some infections, as well as a flexible sealant. Hence the name "mastic" (as in "mastication" which means "chewing" from the latin verb "masticare" "to chew")
It has the unusual characteristic of staying flexible and not going hard and cracking, so it has been used as a sealant for an indefinite period.
It is relatively expensive to produce, so is seldom used as a building sealant now. It is still used as a (high-priced) chewing gum and has a scent and flavour that some people like so is also used in cooking.
In the days when trade names and descriptions did not have to be accurate, any flexible building sealant might have been sold as a mastic. So you can't trust the maker's name and you won't be able to guess what ingredients have been used.