Bird droppings stain limestone

Q. I have a question about cleaning limestone. We had new stairs installed this past summer and the tops are limestone. For about three weeks in August, there are berry trees in the neighborhood that the birds eat, and well, I guess you get the picture. We tried power-washing and used a cleaner designed for the power-washer, but the stains remain. Someone recommended "muronic" (sp?) acid, but I'm hesitant. Do you have any suggestions?

A. You are right to hesitate before using muriatic acid; it is a very potent chemical that will etch the limestone. If you do not mind having the tops of the limestone etched (made rough, somewhat eaten up), you can try using it. But be extremely cautious, as it will cause severe burns if it comes in contact with your skin or clothing.

Use old clothes, heavy rubber gloves and safety glasses. Mix one part muriatic acid to seven parts warm water by pouring the acid slowly into a plastic container like a drywall compound bucket. Do not use metal containers or tools. Cover all areas around the limestone with plastic and wet the stones thoroughly. Apply the mixture with a garden sprayer under very low pressure to avoid spraying beyond the limestone. Or brush it on. Immediately scrub the stones with a stiff-bristle brush and let it sit for a minute. Rinse thoroughly with lots of water. You may need to repeat the procedure.

A safer way is to make a poultice with a product such as Comet - as long as it does not contain bleach - and ammonia. (Be aware that mixing ammonia and bleach creates a mustard-like gas and can be fatal.) Make it into a creamy paste, wet the stones and apply it to the stained areas with a plastic spatula or similar tool. Cover it with Saran wrap and leave it for 24 hours. Rinse thoroughly.

You should consider sealing the limestone caps with an exterior marble sealer that you should be able to purchase from hardware or box stores. Choose the toughest sealer you can find like Stone Tech's Bullet Proof Sealer. You may also want to try StoneTech Stone & Tile Cleaner. You can buy both on their Web site, www.stonetechstore.com. Their products can be shipped to Canada.

However, bird droppings, if that is the problem, are very alkaline and they will eventually cause the deterioration of any sealer except epoxy. You can get clear epoxy from No Skidding, a Toronto-based company with a U.S. shipping warehouse in Buffalo, N.Y., for U.S. customers. Their Web site is www.noskidding.com, (800) 375-0571. This will give you a permanent seal if you don't mind a slight sheen.

Q. Is it a good idea to install a third pane of glass over double-glazed awning windows? I have done so on eight of my windows, but an energy auditor seemed quite skeptical when I asked him about it. I have more windows to do. Also, where can I buy decorative panels with an open pattern that were available everywhere years ago? Home Depot, Lowe's and building supply stores tell me that they have never heard of such things. I need it for a heat vent under the bathroom sink.

A. Triple-glazing windows is a very good idea to increase their energy efficiency. Since you have already done several windows, you seem to have a system of your own. Another choice is to install Magnetite acrylic storm windows that were originally developed by MIT. The magnetic frames are now sold by Magnetite Windows in Baton Rouge, La., (800) 467-6849. You will have to get the acrylic glazing from a local source.

If you are good at repairs, you can make the panels and install them yourself. Acrylic glazing is far more energy-efficient than glass and also protects from the sun's UV rays.

For your heat-vent question, try www.rensup.com. Enter "grilles" in the search box and click on "search." You'll find many grilles in cast aluminum, steel and brass of different sizes. If you do not have access to the Internet, call their toll-free number (800) 659-2211 for a catalog.

Q. A post that is part of my stockade fence is loose. When the wind blows, the fence rocks back and forth and makes the post weaker. Can I fix this myself? I am a senior citizen and don't want to be cheated.

A. If the post is in good condition - not rotted - you can buy Quikrete Fast-Setting Concrete or Sakrete Fence Post Concrete Mix in building-supply, hardware or box stores like Home Depot or Lowe's. These stores may carry similar products under different brand names. Follow instructions on the package. Some of these products only come in 50-pound bags - probably more than you need. And cement-based products do not keep well. Be sure that you mix the dry ingredients thoroughly as they have a tendency to segregate when stored for a long time.

Q. I have read your column for as long as I can remember and always enjoy it and learn a lot. Would you please help me with this? About six years ago, I purchased new vinyl, double-insulated glass with argon gas, windows from a company called Farley Windows through Bonnette Supply in Swanton, Vt.

They are double-hung windows. I had a professional carpenter - who had done other work for me in the past - install them. The windows are very nice looking but are very drafty and cold and have been since day one. I recently had the factory man look at them, and he said the glass in the windows is still sealed. Is there any way to attach a sheet of plastic or Lexan (very expensive to purchase) for the winter months? I was thinking of cutting Lexan or sheets of plastic to exact size and sliding it between the screen and the window to cut airflow from outside.

The plastic sheets or Lexan could be one-sixteenth of an inch thick or even thinner. The problem is that I think the wind will blow it inward and allow a great deal of air through and get noisy. It would only be tight at the point where the two windows come together to lock. I realize that I could put regular plastic on the inside and use a hair dryer to smooth out the creases, but I am afraid that the two-sided tape may damage the interior wood trim. This process also has to be applied each year for the heating season and detracts from the beauty of the windows.

A. The glass in the window may still be sealed, but the air leakage occurs around the sashes.

Your best long-term solution is to make, or have made, and install magnetic storm windows. Magnetite storm windows, originally developed by MIT, can be put on in the fall and removed in the spring while a discreet metal frame or strip remains on the window frame. They are expensive, but over the years they should reduce your energy bill and immediately add to your comfort. Also keep in mind that acrylic glazing is far more energy-efficient than glass, so it's an improvement all around.

Q. We have a strange-looking cement sidewalk going around the back and side of our house. When the sun shines for a few days, it is a normal off-white color, but as soon as it rains, it turns moss green and may stay that way for two or three days. Would power-washing with a Clorox-bleach solution help, or would the green color return with the next downpour? The sidewalk is about 50 years old.

A. The mottled, green discoloration of your concrete sidewalk is due to its age and the fact that concrete absorbs water at different rates because its porosity varies throughout its entire surface. Over the years, a mildew-like growth has developed, and that is what you see when rain activates it. When the sun shines on it for several days, it bleaches it harmlessly. Power-washing with bleach is likely to leave the concrete with a light-colored mottled effect for that very reason: It will absorb the bleach solution at different rates. Instead, try power-washing with plain water and see whether that removes the green stains. If it doesn't, and you wish to do the job yourself, mix 1-part muriatic acid (buy in hardware or paint stores) with 5-parts clean water in a 5-gallon plastic bucket. Be very careful that you pour the acid gently into the water and not the water into the acid. Do not use any metal utensils or tools. Wear old clothes and skin protection, including heavy rubber gloves. Using a stiff-bristle brush, scrub the solution over the sidewalk in sections until the fizzing stops - it will not take long - and rinse thoroughly immediately. When you have achieved the desired results, coat the concrete with a penetrating waterproofing sealer like Barricade Silane 40; you should be able to buy it in masonry supply stores.

Q. Please help! How do you get rid of rats? I have big holes in my yard and we also had rats in my house. I had a room added 20 years ago. It was built on the old foundation and it has a 3-foot crawl space with an opening into my cellar that's about 2-feet by 2-feet. The building in my yard was torn down and just buried in the ground. The sewer was not closed properly. I live a block from the river. Every year, I have this problem. I had an exterminator over, and he got a few rats. But they are back. Is there a foam like the one used in attics that would keep them out, if I used it in the crawl space? I read your column all the time, enjoy it and learn a lot. That is where I saw the mention of the attic foam. I am a 78-year-old female. Thank you for any help or advice you can give me.

A. I am not sure where you want to use the foam. Are you asking if you can seal the sewer line in the crawl space with it, fill the entire crawl space with it or seal the opening into the cellar with it? If the old sewer line from the torn down building was not properly sealed, a plumber can do it with a proper cap. But it would seem that the sewer line should still be used by the rest of the house, unless it has what is known as a TY that serviced the old torn-down part. I am not clear about what you asked.

Have you contacted the health department of your city? Is there something that it can do or recommend? If rats are entering your house, a pest-management professional should be able to find where they come in and seal their entry points. That's your main goal, as you can't keep them out of your yard if they come from the river. This is a very unhealthy situation, and you should have it taken care of as soon as possible.

• Henri de Marne's column appears Sundays. He was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. Write to him in care of the Daily Herald, P.O. Box 280, Arlington Heights, IL 60006, or via e-mail at henridemarne@gmavt.net.

© 2009, United Feature Syndicate Inc.