Q: When we had our house built 15 years ago we used very light-colored cedar shingles. We were told that nothing could prevent them from turning black -- and in about a year or two they did get very dark. We are now completing a new wing to the house, using the same kind of shingles. Is there any way we can treat them so they will stay the original color?

A: Applying a clear wood preservative to the shingles will slow the process and keep them from getting as dark as they would otherwise, but you will have to renew this every two or three years. Also, you can apply a bleaching stain (made for cedar shingles). It will slightly darken them at first, but they will then weather to a silvery gray rather than turn dark as yours did.

Q: I would like to refinish two 30-year-old pitted aluminum doors. The liquid aluminum cleaners I tried did no good. Should I use a steel brush and then paint the doors white or aluminum?

A: I suggest a thorough cleaning with strong detergent, then rubbing with medium grit steel wool and then fine wool until the surface feels reasonably smooth. Wash again and allow to dry thoroughly. Apply metal primer and follow with coat of enamel.