Frederick M. Hueston, PhD  

Stone Care Consultant 

I was sitting at the local greasy spoon and talking to this gentleman about our space program. Come to find out, he was a retired Rocket Scientist who’d worked for NASA most of his career.     

He had some pretty interesting stories but he was one of those know-it-all types. Every time I tried to interject something, he would come back with his opinion and an explanation. This conversation was going nowhere since he was the only one talking.  

I finished my breakfast and headed out the door to walk across the street to my office. As I walked across the street, it reminded me of the time a few years back when I was called in by NASA to solve a problem they had with a granite memorial.  Here is what happened:

I got a call from the curator at what is called The Space Mirror at Cape Canaveral. The Space Mirror is a large granite wall that has the names of the astronauts who have died, carved into the granite. He said they had some streaks on the granite that needed to be cleaned off and was wondering if I could come take a look to see what would clean them. 

I asked if he knew what the streaks were, and he said, “We certainly do.” He then proceeded to tell me that a NASA scientist came out and took some samples of the streaking material and had them analyzed. He said he would show me the report when I came out there. Well, this was an opportunity for me to work with NASA, so I fired up the ole Woody and headed out to the cape.

I arrived at the main gate and told the Barny Fife-looking guard who I was and who I was told to see. He gave me a look as if I was some kind of terrorist. He finally cleared me and I headed to the main office where I was to meet Mr. Curator.  

I went to the main reception desk and again got the “are you a terrorist?” look. The receptionist picked up the phone and led me into Mr. Curator’s office.  

He was a very tall man, nearly seven feet, and had a clean-cut, astronaut-type look to him. Short hair, no glasses, etc. He gave me a 4-inch thick looseleaf binder and proudly stated that this was the report of the work the scientist did on the streaks. 

I asked, “Can I take a few minutes to scan the report and then we can take a look at the problem?” He nodded and left his office, giving me about 30 minutes to look at the report. 

It was filled with all kinds of data and graphs. I finally turned to the very end to cut to the chase. The conclusion was that the streaks were silicone residue. Well, I had to see this to believe it, so off we went to look at the problem up-close.

The first thing I noticed was that the streaks were only running down from the letters and from the joints between the stone panels. Upon closer inspection, I noticed that the joints and the letters contained a soft silicone caulking. The caulking appeared intact and didn’t seem to be falling apart or bleeding. I stepped back and started my interrogation with Mr. Curator. I asked, “How long has the wall been up?”   

“Five years.”

“When did you start noticing the streaking?” 

“About a year ago.”

“Has there been any new caulk placed in the joints recently?” 

“No, the caulk is original.”

I started scratching my head. For the life of me, this did not make any sense at all. If these streaks are silicone residue, why did it take nearly four years for it to start streaking?  I just stood there staring at the wall, when all of sudden I noticed something. 

There were several pigeons sitting on the top. What was unusual about this was that there weren’t a lot of pigeon droppings on the wall. So, I turned to Mr. Curator and asked him how often they cleaned this wall. 

He told me they have to clean it every day, otherwise it would be covered in pigeon droppings.  

I asked what they cleaned it with, and he said, “Let’s go look.” 

We walked down under the wall through a door where there were several gallons of cleaner. I picked up one, turned it over, and discovered the cleaner was alkaline with a Ph. of 13. Now I had a strong idea what this streaking was– and it wasn’t silicone.  

I asked Mr. Curator if I could perform a couple of nondestructive tests on the streaks. He told me to go for it.  

I went out to the Woody and grabbed some marble polishing powder and my cordless polisher. I placed some powder on the pad, added some water, and went to town on the streaks. They came right off.  

Mr. Curator was watching the entire time and was pleased with the results. Now I had to break it to him that the NASA scientist’s conclusions were incorrect. I cleaned up and was placing my equipment back in the Woody when I turned and told him that the streaks were not silicon residue. 

He looked at me like I was from outer space (no pun intended). He told me that there was a team of NASA top scientists working on this problem and they are never wrong.  

I told him, “They weren’t exactly wrong but they came to the wrong conclusion.” I told him I could prove it, but would need to make a phone call. 

We headed back to his office and when we arrived, I placed a call to the contractor who built the wall, who just so happened to be a friend of mine. I asked him one question. “Mark,” I said, “when you were done constructing the wall, did you seal it with anything?” 

He told me they used a silicon impregnator. I said thanks, hung up, then turned to Mr. Curator and told him the silicon they were detecting was from the silicone sealer that was used, not from the silicone caulking. I told him that the streaks were alkaline residue from the cleaner that wasn’t being thoroughly rinsed.  

He thanked me and I gave him a name of a restoration contractor who could clean the streaks off.  I was driving back to my office and thought: Stone Detective, one, Rocket Scientist, zero.

The Stone Detective is a fictional character created by Fred Hueston, written to be entertaining and educational. He 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 any email comments to him at