Slippery Rock Gazette

Frederick M. Hueston, PhD

The holidays are finally over – well, at least Thanksgiving, Christmas, Hanukkah and other assorted celebrations. Now it’s back to work and my regular routine. So, I headed off for a cup of joe at my favorite greasy spoon and to wait for my first case of the New Year. 

I left my office and, no sooner than I got out of the door, my phone rang. I flipped it open and said, “Hello, The Stone Detective.” Yes, I still have a flip phone, in case you’re wondering.  The voice on the other end asked if I knew anything about rust stains in granite countertops. I told him that yes, I wrote the book on stains and stain removal on stone and other porous surfaces. He said, “Good, because I have a real problem.”

“I’m listening,” I said in my best Frasier Crane voice. 

He told me he was a builder and had 26 condo units with new granite countertops, and all the backsplash seams are staining with what appeared to be rust. Well, that sparked my interest, since I never heard of just the seams rusting. My first thought was that it wasn’t rust and that the fabricator may have used a silicone or caulk that was bleeding into the granite.  

He added that the condos were all sold, several customers had already moved in, and he needed me to get out there right away to see what could be done. I asked him where, and it was only a few miles from me. So, I told him I needed my caffeine fix first and I would be there sometime this morning. 

I finished my coffee and was off to my first inspection of the New Year.  My first thought was that this would be a simple case. I was convinced it was a caulking / staining issue, since I have seen this many times.  I arrived at the condo complex, which appeared to still be under construction since there was no landscaping and several backhoes working.  I looked for a place to park the ole Woody, preferably somewhere where it wouldn’t get dust all over it.  Finally, I spotted a place across the street, parked and headed over to the complex.  

I entered the front door, and there was a gentleman pacing back and forth in the lobby. I kid you not, this guy looked like the monocle-wearing chappie from the board game Monopoly. Who the heck wears a monocle these days? For a moment, I thought I was dreaming and would soon wake up. 

I walked up to Mr. Monopoly and asked him if he was waiting for me. He stopped, looked up at me, squinted behind the monocle and said, “Who the heck are you?” I told him I was the Stone Detective. He just said, “Oh, well then. Follow me.”

We rode the elevator up to the top floor. The entire time I tried to make conversation, but he ignored me and didn’t say a word. 

We entered the condo unit, which was covered in marble. Everywhere you looked was white marble. It had a sterile look, considering the furniture was also white.  I said, “Nice,” and he said his first word since we entered the condo – “Here,” as we went into the kitchen. 

Yes, granite can rust, but It is not normal for rust stains to appear like this.

He pointed to the backsplash, at a seam behind the sink fixture (see photo).  My first reaction was that it certainly looked like rust, but why was it only in the backsplash seams?

I examined the rest of the countertop, and there was no sign of rust. I asked him if the staining was in every unit, and he said yes.
 My next step was to test the stain to see if it was rust or some mysterious stain. 

I reached in my bag and pulled out a tube of Ammonium Permanganate. This is a gel that is use to test for suspected rust.
The gel is a milky white color, but when rust is present it will turn a dark purple. I placed a small amount on the stain and it immediately turned purple. It was rust for sure, but where was it coming from and why only on the backsplash seams?  

I asked if I could take one of the seams apart. He told me that I couldn’t but there was a unit still under construction, and the fabricator was getting ready to install the backsplashes.

“Perfect,” I said. “Maybe I can see what they are doing.”

We rode back down the elevator to the first floor. We entered the unit, and there were contractors running all over the place. He led me to the kitchen, and there was a worker with a backsplash laying on the counter. I just stood there to watch the installation. Within a minute, I had my answer. The fabricator had placed grooves on the edges of the backsplash. He placed several washers in the groove, similar to what a wood worker calls biscuits. Bingo! He was using standard galvanized washers, and they were quickly rusting in the stone. I looked at Mr. Monopoly, picked up one of the washers and explained they were the source of the rusting, and that was why they were getting the staining. I told him he would have to have all the backsplashes replaced.  He looked at me and said, “OK ,”and told me to send him my report. Another case solved, and the New Year is off to a great start. 

The Stone Detective is a fictional character created by Dr. Frederick M. Hueston, PhD, written to be entertaining and educational. Dr. Fred has written over 33 books on stone and tile installations, fabrication and restoration and also serves as an expert for many legal cases across the world. You can send your email comments to him at fhueston@stoneforensics.com.