Frederick M. Hueston, PhD

It was one of those hot, humid days here in Florida – the kind of day you just want to stay inside and sit in front of the air conditioner. It was so humid you could actually see the humidity in the air. 

I decided to brave the heat for a minute and walk across the street for some of Flo’s famous grilled cheese sandwiches and some sweet tea.  Just as I was about to walk out the door my cell rang. “Stone Detective, here,” I said, as my stomach growled like a bad-tempered watch dog. 

The voice on the other end was very excited and had a strong accent. He was so worked up I was having trouble understanding him. He finally got me to understand that he was the manager of a high rise in Palm Beach. He had a condo owner that had installed white marble tile in his condo. 

And I mean the entire condo, to the tune of 7,000 square feet. Not only was this flooring, but walls, showers, et cetera. He said the condo was still under construction and the owner was complaining because the stone was turning brown. He was wondering if could come take a look. Fortunately, Palm Beach is a short two-hour drive for me. So I told him I could be there that afternoon. That is, after my grilled cheese and sweet tea lunch. I was already out the door and over to see Flo.

Lunch was just as an expected – delicious, as always. I finished up and even managed to put away a slice of homemade hot apple pie with a scoop of vanilla ice cream. (Bet I’m making you hungry!)

I got in the old Woody, turned the air on high (love my retrofitted AC), and headed down the highway. 

I thought about taking the Harley but it was too humid. Still, it was a nice drive, not much traffic.

I arrived at Jose’s office, which was across the street from the condo complex. I tried to open the door but it was locked. I was a few minutes early so I figured I would wait a bit and see if he showed up. 

When my set time had passed, I told myself I’d wait another 10 minutes and then I would call him. Just I was about to dial the phone number Jose gave me, I noticed a door bell next to the door. Duh. So, I pressed it, and within seconds someone (Jose?) came to the door. Boy, I wish I would have seen it sooner, now that I was dripping sweat from the humidity. 

Well, it was Jose, and he took me back to his office and explained what we were about to see. More importantly, he explained that the owner is very wealthy and believes the problem is the installer’s fault. I told him, “Let’s take a look and see what I can discover.”

large format marble tiles on the floor were turning yellow and brown
large format marble tiles on the floor were turning yellow and brown

We walked across the street, entered the building and headed toward the elevators. The condo was on the top floor. We walked into the condo, and the first thing I noticed was that the large format marble tiles on the floor were turning yellow and brown. Not all of them, but I would estimate about 80 percent of them.  I looked over the entire condo, and I knew right away what the problem was. The stone was oxidizing! This is typical with white marble exposed to moisture. 

But this was over 20 floors up, and wasn’t on a ground floor where moisture could get in. I was pretty sure it had not been exposed to any flooding. So why was stone oxidizing — in other words, why was it rusting? 

The answer was simple. The minute I walked in the condo, I noticed that the air conditioning was off. I walked over to the thermostat and the temperature was 84 degrees Fahrenheit. Luckily, the thermostat also had a humidity reading —and it was 64 percent  That, my folks, is humid.

I took out my cell phone, called up a weather app, and looked up the humidity in Palm Beach. It was also 64 percent. I asked how long the air conditioning was off, and Jose told me that the owner did not want to pay the AC bill, so he had it turned off… for over three months, so far! I looked at Jose and said, “That’s the problem. The high humidity is causing the iron in the marble to oxidize.”

Unfortunately, the staining was too widespread to attempt to remove it. I recommended it all be replaced, but this time turn the darn air on and have the owner pay the power bill. It would be cheaper than replacing the marble, again. 

Another case solved. Too bad I didn’t bring my bathing suit, I could have gone to the beach while I was there!


Fred Hueston is world-renowned expert on stone and tile installation, fabrication and restoration issues. He serves as an expert witness and owner’s rep for projects across the world. He also trains others on these topics. His many cases can be seen on his website at .

For more details on his training seminars, see the training section at for  the Stone Inspection and Troubleshooting correspondence course, or call 321-514-6845.

Dr. Fred’s next live class in Las Vegas is January 16-19, 2017.