Q. Someone really messed up my bluestone hearth (8 by 2 feet) by putting Valoil on it. Denatured alcohol diluted with water was used to eliminate stains, but it left rings where it was poured on. Now what do I do? It's really a mess.

EVELYN CUOCO, Beverly

A. I think the only thing you can do to fix the mess is to sand the bluestone with fine sandpaper. Try a small area; you will lighten it up but you will also remove stains and the oil, by revealing new stone. If sanding a small area is satisfactory, then do the whole hearth with a power sander. But with fine sandpaper, and lightly.

Then, you can leave the bluestone alone and take chances with staining (it is very absorbent and stains will be inevitable), or apply a masonry sealer or tile sealer, which will make the stone a little more water resistant and less likely to stain. This sealer should be reapplied every two years or so. It will not change the color or finish of the stone. A third treatment is oiling, but with your experience with Valoil, you may not want to do it. If you do, this is how. Make a mix of 1 part boiled linseed oil and 1 part paint thinner. Apply this liberally, let it sit for 15 minutes, then wipe it dry with a dry cloth. If you don't wipe it dry (that is, remove excess oil), it will stay sticky for a long, long time. This treatment will seal the stone just as the masonry sealer does, but it will darken it.

Q. I am extending my raised hearth by building a frame to hold the new bricks. I was told to use cement board as a base for the bricks. Is that the same as WonderBoard?

TIM KANE, Merrimack, N.H.

A. Yes, WonderBoard is cement board, and there are other brand names as well. The board is made of a sand concrete reinforced by fiberglass, and it is an excellent base for brick or tile.