by Pat Smithson
I have black slate that has been down 35 yr and was sealed then.
Throughout the years it has worn most of the sealer off but the grout is dirty and slate has white spots on it where I think water, etc., has gotten under the sealer.
Any ideas of something not so toxic that would remove the sealer and clean the grout.
From what you have described to me is that your slate tile was most likely coated to give some sort of finish.
Most people tell me what you've said that the sealer is wearing out in the high traffic areas.
A sealer is applied to a natural stone to protect from staining and a coating is applied to put a desired finish on the stone.
I never recommend any coating on any stone, but many people do it anyway. They forget that natural stone is natural and should be left natural.
But, they want to create an unnatural look to there natural stone. This is where problems occur whether it's in a few months or a few years.
If the natural stone is cleaned and re-coated every so often (maintained), and maybe even stripped and re-coated, then you can maintain the look.
Both the clean and re-coat and the strip and re-coat are costly. You are at the point of a strip and re-coat if you want the same look as before.
You will need the help of strippers that are most likely toxic. I only say this, because you say the coating was put on 35 years ago, and I doubt they used water based coatings like they do today.
Paint strippers or coating removers will most likely be needed. Not a fun task and a task I would not want to do. This could be costly.
Find a few different water based strippers and do a test to see if they will work, before looking for the toxic coating removers. If the water based strippers work you're in luck.
I hope every thing works out for you.