(possibly) silly question

**eddiemck** · 09-10-2009

if a ready mix adhesive like BAL white star can stick a porous ceramic tile to the non porous face of an existing ceramic tile, why can't it stick a non porous porcelain tile to a porous substrate like plaster. logic suggests it should be able to but it says not to on the tin. random question i know but if anyone knows the answer it'll stop my mind wondering...

**Ajax123** · 10-10-2009

This will probably be to do with the take up rate of the porous surfaces. If the adhesive carrier is absorbed into the 2 porous surfaces too quickly it will dessicate i.e. dry out before it has time to set properly.

Often some of these rules seem obscure and to the logical mind unreasonable. Most responsible manufacturers issues these rules based on research data so they ought to be followed. In many cases where the rules are ignored on the basis that "I have done it a certain way for years and never had a problem" can be extremely costly on the one time it does go wrong. These issues also cause major arguments because if you get away with it so many times and then it goes wrong it becomes very difficult to understand. Often the "getting away with it" is a function of the products being robust enough to withstand a certain level of abuse combined with pure blind luck.

If it says don't so it - don't do it.

**eddiemck** · 10-10-2009

Thanks, i definitely wasn't about to try it out; as you said way too risky and potentially costly. just wanted to see whether anyone had a plausible answer and what you say about drying rates makes sense. i can sleep better now, thanks.