Frederick M. Hueston, PhD

Stone Care Consultant

It was one of those wonderfully spring mornings. I woke up to birds singing and the sun just peeking through the clouds.

I got up out of bed, opened the window and thought what a great day it was going to be. At my age, I thought I had seen everything, at least as far as the stone industry was concerned…and then the phone rang. “Stone Detective, here,” I said in a half-awake voice.

The caller had a scratchy voice and sounded desperate. He told me he was a stone mason and was working on a limestone wall at a large estate of someone really famous. He said he had a problem with mold and moss on the wall and was wondering if I could come by and take a look.

My first reaction was just to tell him how to remove it. I have done it many times, but something in my gut was telling me to go over there and take a look. Well, I was in a good mood and told him I could swing by later that morning. I got dressed and headed out the door for my morning ritual of a cup of jo and the morning newspaper at the local greasy spoon.

After several cups and some really intelligent conversation with the locals–not–I hopped in the Woody and headed over to the jobsite where the stone mason was working.

I pulled up to this elaborate gate with the initials BW on it. I’ll let you guess what famous person this was. There was a long limestone wall that had to be over a hundred years old. It was very difficult to see the wall since it was caked with green moss and other biological growth. I started to come up with a plan in my head of how to remove it, and then I spotted the stone mason working on a new wall.

I pulled the ole Woody off to the side and he came running over to me. He shook my hand and started rambling on and on about the new limestone wall. I looked over at what he had constructed and it was a great job.

I told him it looked great and that I could see the problem with the old wall. He looked at me as if I had stepped off the Starship Enterprise and said, “What problem?”

I pointed over at the old wall and said, “The moss and all that growth.”

“Oh,” he said, “no, that’s not the problem at all. The problem is with the new wall.” Now I was getting confused. I thought he had called me about a moss issue, so I asked him, “Didn’t you tell me on the phone that you had a moss problem?”

“Yes,” he said, and then he said the following which total floored me. “I need to figure out a way to get moss and all those fungi to grow on the new wall, and quickly.”

Now I have heard everything. Apparently, the owner wanted the new wall to look like the old wall. So, I scratched my head and just stood there like a deer caught in headlights. I didn’t know what to say and I couldn’t think of an easy answer. I told him I would get back to him later that afternoon after I did a little research.

I headed back to my office with the question of how you grow moss really fast on a limestone wall. I pulled up to the office and it was about lunch time, so I walked across the street to the local pub to grab a ruben and maybe a beer.

I walked in and noticed that stale beer smell. It was like someone had spilled a beer on the floor and no one had cleaned it up. Little did I know, that the smell of beer would be the answer to my moss problem. I finished my sandwich and several beers, and headed back to my office for some research.

I got on the computer and typed in “Growing Moss” and couldn’t find a darn thing. Now I was getting frustrated. I started staring at the wall across from my desk and noticed an old photo I had of my college roommates. I looked at the photo and realized that my best friend in college was now a professor at the local university and his specialty was fungus. So, I picked up the phone and gave him a call.

After over a half an hour of reminiscing about the good ole days, I got to my problem. He laughed and said, “Well, that’s easy.”

“For you, maybe,” I said. He told me all I needed was some yeast, yogurt and stale beer. I started laughing then, and told him he was out of his mind. He told me that moss and fungi needed not only a moist environment but they needed a food sources as well.

He said to mix the yogurt, yeast and beer into a paste and paint it on the wall. Next, take some of the moss off the old wall and put it on the new wall. He said that next to no time, the moss will start growing on the new wall.

Well, this old man learned something new, and, hopefully, so did you. I have to admit that I never saw that one coming!

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