Originally Posted by Craigthor
Not completely true, I have resealed a dozen tanks at this point and all are still up and running 2-5 years later with no leaks.
Until 2 years ago I was an engineer for Corning. For the last 12 years our section worked on various ways to bond glass to everything under the sun, including other glass products. Very simply put silicone adhesives bond to glass by filling the microscopic pores on the surface. This gives them the "claws" to hang onto. Once silicone adhesive is on the glass those pores are filled. You can cut the excess off and rub all day with various chemical but it just doesn't give up the original purchase.
The only way to remove it completely is to mill the glass down 1/000 of an inch.
I am looking around here for the engineering data but 2 years gone is a long time to keep things sorted. By memory, I think you can expect that cleaned up glass will have a lower bond strength by 20%-25% Just plain silicone adhesive to cured silicone adhesive is about 65% percent that of a new and clean bond.
Soon as I find all that data I will post. There is a lot of bad info out there.
One caveat. I am speaking only of Dow-Corning Silicone adhesives.