Q: I own a frame house with a cinder-block basement. When I painted the cinder-block walls last winter I noticed a pure white crystal-like substance "growing" or pushing its way out through the cinder blocks on certain walls. The wall on which this was most noticeable was the one wall that has no windows. Before paintng the basement walls I treated them with a heavy, white-colored sealant that was supposed to prevent moisture; then I used a good-quality oil-base paint throughout the basement. A few months have passed, and now I notice that the white crystal-like substance seems to be coming back, pushing the paint off in the process. What can that ugly stuff be, and how can I get rid of it?

A: I think your problem is due to a condition called efflorescence. This is the development of a salt-like crystalline growth that often develops when moisture comes in contact with excess alkali -- a condition often encountered in cinder-block construction.

To get rid of it first scrape off any loose paint, then wash with a muriatic acid solution. Mix one part acid (sold in paint and hardware stores) with three parts water in a plastic pail and scrub it on. Wear rubber gloves and safety goggles. Let dry on the surface, then rinse off with plenty of water. This will neutralize the alkaline salts but, unfortunately, it does nt guarantee that the condition will not return if there is still a moisture problem in that wall. It might pay to try a different sealer -- perhaps one of the stronger epoxy types. When you repaint, don't use an oil paint -- use a latex masonry sealer recommended for use on basement walls.

Q: The cedar paneling in my kitchen is untreated, but now its 30-year-old sheen becomes sticky when the weather is humid. How can I remove this sticky film without removing the color and the gloss of the cedar?

A: If the cedar has a gloss or a "30-year-old sheen," it was treated sometime in the past; untreated wood has no sheen or gloss. What you have now is an accumulation of dirt and soil from exposure to the air -- and to cooking smoke and vapors -- over the years. You can probably remove the sticky film by wiping down with a liquid furniture cleaner and polish. If this doesn't work, you may have to use a nonflammable dry-cleaning liquid or degreaser (sold in most hardware stores). This will not harm or dull most finishes, but I would test first in an inconspicuous corner before going ahead with the entire wall.

Q: Our aluminum siding is shedding. A white powdery chalk comes off and leaves dirty blotches on the outside. What can we do about this?

A: You can scrub a section with a strong solution of powdered detergent, using a stiff brush. If this works, go ahead with the rest of the siding. If it still looks blotchy, you will have to repaint, because the original finish is wearing off. Any good house paint can be used, but there are also special latex types now made for use on aluminum siding that will probably cover better.

Questions about home repair problems should be addressed to Bernard Gladstone, care of The New York Times Syndication Sales Corp., 200 Park Avenue, New York, N.Y. 10166.