Your Place: Use ammonia to remove coating from glass

Question:

We moved into a home with 20-year-old sliding glass doors that were treated with what appears to be a thin plastic coating or plastic shield for sun glare.

Is there any way to remove this coating?

One slider has clouded over, and the coating has chipped and blistered in spots. It could be a broken seal, but the areas that have no coating are perfectly clear.

Answer: The best solution I've read is from my buddies the Carey Bros. of San Francisco: Spray the coating with ammonia, cover it immediately with Saran Wrap, wait 45 minutes, and then scrape it off with a broad-blade putty knife.

It makes perfect sense - sort of the same technique for removing wallpaper: wet it enough and you can remove it and not the plaster wall behind it.

That's straight ammonia, according to the Careys, so ventilate well and wear protective gear, goggles, and mask.

Q: I have a shingle roof, about 6 years old, on the north side, and I am getting mold and mildew on the shingles.

I want to be cautious cleaning because I do not want to remove the grit on the shingles - this is what protects them from moisture and water.

I also get the same mold/mildew on the vinyl siding on the north side, but this is easily rectified.

A: There are roofing companies who specialize in removing the mold and mildew without compromising the shingles.

That means the product is free of chlorine bleach, which can damage the shingles.

There is also the belief that the problem is the result of a change in the composition of shingles from rags to ground limestone, which has resulted in black algae stains on the shady sides of the roof.

Green mildew, the experts say, feeds off the black algae. The solution is zinc or copper strips nailed to the roof above the affected shingles.

The experts say that neither the algae nor mildew do anything to the roof, except make it slippery.

I personally believe the issue is cosmetic, not structural, because that's what the roofers and materials manufacturers I've interviewed over the last 25 years have told me.

I have some mildew near the dormer on the front of my house, and for 12 years, the area gets mildewy in the winter when the area is completely shaded. The green disappears with the arrival of the spring/summer sun.

I've checked the area, and there seems to be nothing wrong with the shingles.

Q: What do you think of travertine for a bathroom vanity countertop? I know that it's a porous material, so I'm worried about staining and etching.

There is a marble retailer that fills it with cement and polishes it. This is for a 61-inch, double-sink countertop that does get heavy use. It will be exposed to water, cosmetics, and other things.

I'm sure granite would be better; however, I'm not finding any granite in the beige tones that I want. I could always go with Corian, but the travertine is really quite beautiful.

A: Your concerns about travertine, a type of limestone, as a bathroom countertop material are the same ones I've seen discussed on the Internet.

From an English site: Travertine can be used for countertops, but it's not recommended. It is easy to scratch and etch. It works well for flooring, accessories and smaller spaces.

Not all travertines are capable of the polished high-gloss finish - only the harder types. This stone will never achieve the same glossy finish as marble and granite will.

Travertine should be sealed with a penetrating sealer.

Your call.