I've never had issues with TT. As long as the glass is prepared correctly and you don't spray in hot or cold conditions, I don't see a problem. I NEVER Seal a back glass "for the hell of it" - I ONLY seal them when they are deteriorating to a point where it will get worse over time.
Not sure what to do now as just checked my kiss back glass and has just started to bubble in the middle of the kiss wording.Was a 10/10 now down to 8/10 not happy. 
Have used TT before with no problems but not on a bally repro before.Should i go a head and do it as the bubbling only going to get worse or is there a better product to use.
Even a bigger problem is that i have a few other nos black glass and don't wont it to happen to them as well as all nos.Was going to TT them as well but don't no what to do or use now. 
If i don't do something with them now ,they will start to bubble,and i will be not happy. 
What other products can i use and i don't wont to spray them and then check 3 month later and find out that i stuffed them all.
If I were you Craig ;
Leave NOS backglasses alone !
I would consider sealing the KISS glass if it looks like flaking.
Lets remember WHY this is happening.. The main reason is that when these machines were operated, they were left on all day, nearly everyday. So the heat from the #44 lamps basically "toasted" the backglass over 20 - 30 years.
Now this was not too bad on EMs, but lethal on some SS. There are other factors such as different printing process and the thickness of the paint - but all glasses were installed in perfect condition.
I ALWAYS use #47 globes in the backbox of any machine. IF you starte to see wear and tear - remove half of the globes - this is what was done "in the old days" to save the glass from deterioration AND to release the strain on the power supply.
There are other products out there. Steve Young used to have a product called "save my glass" (I think it was called that) - and it was the best product to use.
Clay (Marvin's Site) has used TT for years without an issue - I think his suggestion would be to "perfect the process".
