Hello everyone!

I am doing a research and home experiment on the subject of "Marble discoloration in wet areas". Based on different facts and testing, I can say that in many cases when marble shower floor is getting permanently dark and discolored it is caused by impregnating sealers trapping moisture inside the stone.

I personally like using impregnators. I am not trying to prove that sealer in general is a bad product. We all know how it performs in dry areas and it definitely makes maintenance process easier. At same time, it looks like the idea to use impregnators on natural stone in wet areas is missing an important fact about moisture entrapment.

This particular research is not driven just by me. All the modules for our testing are constructed with materials that were donated by different contractors, tile & stone stores and manufacturers. So many people are interested and have helped me with their advises. Our goal is to test different methods and then to write an educational article on this subject so that people can be informed.

I myself experienced this problem. Many very good professionals who I contacted trying to find out the cause and the solution told me they are aware of this issue and also had it in the past but they didn't know exactly why the discoloration was happening and how they could have avoided it.

I spent tens of hours searching in internet and read different technical articles. I tried to find answers in TCNA Handbook, NTCA Reference Manual and on NSI (MIA) website and there were no answers. I read tens of posts at John Bridges forum and Houzz and still was confused. After all that, I found articles written by Fred Hueston from Stone Forensics (https://stoneforensics.com/our-team) and decided to contact him. He sincerely offered me his help in the investigation. Based on different facts, we came to the conclusion that in my particular situation it is most likely that sealer is not allowing moisture to evaporate. Dr. Fred already had same concerns about the use of sealer in wet areas and discussed this in one of his internet The Stone & Tile show talks.

I came to the idea of testing the performance of impregnating sealers on marble in wet areas and find out the best method that will help contractors to avoid problems with marble discoloration. We will also try to fix a discolored sealed marble by removing the sealer. Again, we want to write a detailed educational article.

I am also trying to get information about the European understanding for installing marble in wet areas. Searching German Google I haven't found a single picture or article regarding this problem. A managing director of one German tile & stone association told me impregnators are usually not applied on marble in wet areas. We already know same thing from a quarry owner from Turkey (I want to thank Metin Gungor from Decor Construction LLC, NJ for his help).

You can check out our progress at the following link: http://www.startile.us/tiling-by-the-book-blog

I think you may find very interesting the following comment made by Dr. Fred Hueston regarding the use of impregnating sealers on marble in wet areas. Very informative and clear!

"Let me also offer an explanation: Impregnating sealers all claim to be vapor permeable.. Which simple means they will allow water vapor to penetrate into the stone. A shower is an area of high vapor. Even mild to hot water will produce a vapor. Once this vapor penetrates the stone it condenses and converts to a liquid. It will only escape once it becomes a vapor again. Since the shower is used in a short period of time it will take a very long time for the water to vaporize..."

Here is a link to Dr. Fred's last radio talk where he discussed the moisture related issues in stone & tile installations: http://www.blogtalkradio.com/drfred/2019/02/07/stone-and-tile-show-moisture-related-issues

I would highly recommend you to listen to it!