A.C., Cambridge

A. That paste is a combination of paste and glue size, which was applied to the wall before the paper was hung. And you're right; water will soften it but it does resist removal, feeling very slippery when you try. So, make a super-strong solution of Spic and Span and water, which will tend to dissolve the paste and make it easier to scrape off. You may have to do it several times. And, at the beginning, if you soften the paste with water, you can scrape a lot of it off with a wide putty knife.

Even if you don't get it all off, you can leave some of it on to dry, and if it is smooth, you can paper right over it. If you plan to paint, you have to remove every trace of it. And that means washing and washing again.

As for relocating the toilet drain, it is possible but not feasible, because it would entail more work and plumbing than is worth the trouble and expense. I wouldn't bother.

Q. What causes mold to form under vinyl wallpaper that is applied to Sheetrock? How can I correct the problem?

ANOTHER WRITER, Hunstsville, Ala.

A. Mold is growing under wallpaper because it was on the wall before the paper was put up. To correct the problem, remove the offending wallaper and all traces of paste and glue sizing left on the wall. Wash with Spic and Span and water, TSP cleaner, or ammonia and water until all traces of sizing and paste are gone. Then treat the wall with a solution one part bleach and three parts water. You could add bleach to the wash water, but don't mix bleach and ammonia, nor add bleach to any other solution except water. Wear skin and eye protection when working with bleach. Rinse the bleach, because bleach will interfere with the glue sizing and wallpaper paste that you must use when re-papering. If you plan to paint instead, the bleach also must be rinsed.

Q. What's an easy way to remove wallpaper from real plaster?

EVELYN ROMAN, Meedham

A. If you have only one room to strip, hot water may be enough. I suggest keeping it really hot on the stove and applying it with a roller. Keep the hot water off the floor and any other surfaces except the walls. After awhile, scrape a test area, then go to work. You can try an additive to warm water. One is called E-Z Gel Wallpaper Remover, which is sold in wallpaper shops. It sticks to the paper, not the floor. Another is Dif Gel, also sold in wallpaper stores. If you have several rooms to strip, then I suggest renting a steamer. As for easy ways, none is, but the steamer is the easiest. If the paper is vinyl coated or painted, none of the above will work because the vinyl or paint prevents the penetration of the steam or water or additive to allow the stripper to soften the paste. You can score the paper by drawing a hand saw's toothy edge down the wall horizontally, making many score marks in a row. Also, there is a gadget on the market, made by Zinsser, called PaperTiger. This tool has several toothed wheels that go in different directions, scoring the paper as you go along. It's a great name for a good tool.

Q. How can I prep dry wall (plasterboard) for wallpapering?

ANDY KELLY, Norwood

A. If the dry wall is not painted, paint with a latex enamel undercoater and apply a second coat of the undercoater or a latex wall paint. Zinsser, a large paint company, makes a special paint for applying paper over. Any of these paints will make the wall water resistant, and are mainly to make it easier to remove the paper (someday) without wrecking the paper face of the plasterboard. After this paint dries, apply glue size, then paper the wall any way you like. Glue size is sold in wallpaper shops, and is essential to the success of your wallpaper job; it allows the paper to be moved and adjusted when it is applied, makes the paper stick better, and, paradoxically, easier to remove when the time comes.

Q. When I removed some vinyl wallpaper, a lot of dried paste was left on the wall. Can I wash that off with TSP? I also have a sand-finish ceiling. Can I paint it with a roller?

FRANK HUGHES, Tewksbury

A. Yes to both questions. You can use TSP (cleaner) or even Spic and Span or any other heavy-duty detergent. In the days of wheat or cellulose paste, it was easy to rinse off. But some of the newer pastes, especially vinyl pastes, are stubborn, and a detergent is necessary. When washing, let that solution stay on the wall for two minutes so it can dissolve the paste, then scrub and rinse. You may have to repeat. And, if the paste is quite thick, you can make things simpler by wetting it enough to soften it, and then scrape as much off as possible with a wide putty knife. Then it will be easier to wash off remaining paste.

As for the sand-finish ceiling, use a roller. A short-nap roller is best, and be sure to put the paint on in thin coats. Someone asked me how one can put on a thin coat of paint with a roller, which by its very nature will apply a thick coat automatically. The answer to that one is: not necessarily. When loading the roller, simply roll some of the paint off on the tray before applying it to the ceiling.

Slow and steady wins the race; logic and common sense will solve most problems.

Q. I found some textured wallpaper that is designed to cover the grooves in old paneling. Will that work, or is there something else I have to do to the grooves?

J.H., Natick

A. There are heavy-duty wall coverings that do, indeed, cover rough surfaces, and the grooves in plywood paneling, but such grooves are fairly deep or wide, and some coverings might dip into the grooves instead of spanning them, in which case the grooves would ghost through the covering.

You can try hanging a strip or two to see if it works. If you see the grooves ghosting through, then you should fill the grooves with joint compound. Filling the grooves once might work, but for a top job, the grooves should be covered three times by the joint compound and sanded smooth. If the covering has a pattern, it might disguise any ghosting of the grooves.

All this elaborate explanation is prompted by the Handyman's own experience. I decided to cover some plywood paneling with a vinyl-coated cloth wallpaper, so I knew I had to fill the grooves. I used one coat of joint compound, sanded it smooth and it was perfect. I thought. When I put on the paper, sure enough, the grooves ghosted through, which drove me slightly bananas, until I finally covered everything with new plasterboard.

Q. I took off the wallpaper in my Victorian house and painted the plaster. Why did it peel and crack after four years?

CHRISTINE HOLDERNESS, Boston

A. Beats the heck out of the handyman, because there could be several reasons, to wit: 1. The paint was applied too thickly. 2. Not all the paste was removed. 3. The wall surface was dirty. 4. The surface was too smooth. 5. It just gave up the ghost after four years, although interior paint should last much, much longer. If you can stand the color, it could last the life of the house.

So, for a cure, you have to scrape off all the loose paint you can, sand to roughen the finish, and feather the edges of the remaining paint. Those edges between paint and no paint can be quite severe, and they will show through new paint every time, unless they too are heavily sanded. And, wash any bare plaster spots to remove any remaining sizing and paste.

Q. Will removing wallpaper from a wall damage it? I took off some paper, but the paper backing to that paper remains. Should I remove that too or can I paper over it? I think the wall is plasterboard. The new paper is prepasted.

JOAN RUNA, Winchester

A. If the wall is plasterboard, I suggest leaving that paper backing on because trying to remove it could damage the plasterboard, simply by gouging and scratching. If you leave it on, paint it with an oil-based primer; don't use latex because it could lift the paper and cause wrinkling.

However, being uncoated paper, it should come off with a minimum of soaking with steam or stripper without wrecking the plasterboard finish. Just use extra care.

If the wall is real plaster, you can strip that uncoated paper quickly with steam or strip0per. At least you should be able to.

When putting up new paper, whether on the painted paper or on bare plaster, size the walls with a glue size, then put up the paper. I also suggest that you use regular vinyl wallpaper paste with the prepasted paper. That might be overkill, but I think the paper behaves better when it is put up with paste.

Q. I am considering painting the wallpaper (one layer, in good condition) in my house. What types of paint can I use? And how can I best apply it.

R.C., Worcester

A. Most wallpaper can be painted. I think it is best to prime first with a latex enamel undercoater, whether the paper is vinyl-coated, uncoated or of the Wall-Tex type (a vinyl-coated, canvas-like covering). This will seal it and help cover any bold patterns, preventing bleeding through the final finish. Then apply a latex wall paint; it can be flat or eggshell. One coat might cover. If not, add a second coat.

As with all painting, thin coats are best; don't try to slather on one coat too thickly to make it cover. As for technique, do the same as you would a plastered wall, with a roller, and a brush to cut in the edges.