ROBERT LEVITOV, Newton

A. Caulking has come a long way in the last 20 years, with silicone among the best. But I don't think you have to go that high; you can get quality caulks called PhenoSeal and PolySeamSeal in the $2-$3 range. I think they work well for the money, are very easily applied because they are pliable, are paintable, and come in colors. You want to be careful with some silicones; some are not paintable

Q. I have to recaulk my bathroom sink, which fits into an opening on the vanity top. Trouble is, I can't get the old caulking off. I tried using a razor scraper, but succeeded only in cutting the caulking. How can I do a proper job?

KEN BOZEK, Chelmsford

A. You have to lift the sink or take it off entirely, because the caulking was installed when the sink was set in the opening. After removing the sink, scrape the old caulking off both the vanity top and the lip of the sink. Then, place a large bead of caulking around the opening, so that when you set the sink in place, it will press down the caulking. Some of the caulking will ooze out from under the lip of the sink; wipe this off with a cloth wet with water or one wet with paint thinner or other solvent. Or, let the caulk set and cut it off with a utility knife.

Q. My Corian vanity top has a Corian backsplash attached to the back and one side of the top. Everything is fine except that the caulking between top and backsplash is yellow (I think it has turned yellow). I would like white. How can I put white caulking in that joint? Can I paint silicone caulking?

LOIS RAND, Concord

A. The fastest and easiest fix is to paint. Some silicones can be painted, some cannot. Use an oil-based indoor-outdoor semigloss enamel and see what happens. If the enamel beads up on the caulking, it cannot be painted. If the paint sticks, you're home free.

A better way is to take off the backsplash, scrape off the yellow caulking from both backsplash and top, and reinstall it with white caulking or grout. A phenolic vinyl caulking is good; Phenoseal and Polyseamseal are two good brands.

Getting the backsplash off is another matter. If it is not glued to the wall, try tapping a wood chisel under the backsplash and prying up. Try softening the caulking with a hair dryer, or by applying alcohol. This might make the work easier. If the backsplash is glued to the wall, more prying may be needed. If the backsplash is screwed from below (under the top), unscrew the screws if they are accessible.

Still another trick: Scrape out some of the yellow caulking (there is not much room between backsplash and top anyway) with a utility knife, then put a bead of white caulking in its place, and smooth that bead out with a wet finger. The caulking will show (it really shouldn't) but it will be neat. And white.

Q. I've been in my 40-year-old house for about two years. I am noticing the baseboard molding pulling away from the wall, leaving a gap, and around the inside window frames. Can I fill them with spackling or wood filler?

JOANNE MONTANA, Canton

A. The gaps appeared because the wood contracted when it lost moisture. It occurs mostly in winter, when the house is dry. The gaps may close a bit in summer, when the wood takes on moisture and expands.

You can fill the gaps, but not with spackling or wood filler, because it hardens up, and when the stuff hardens, and the wood expands and contracts, it will break up that hard filler, making the gap look worse than it does now.

Fill the gaps with a phenolic vinyl caulking compound (Pheno-Seal and Poly-Seamseal, widely sold in stores). Place a bead in the gap and press it in with your fingers. Scrape off excess with a putty knife and clean off residue with a wet sponge before the caulking sets. The caulking will expand and contract with the wood and will keep the gap filled.

Q. In the five-year-old house I just bought, there is a gap between the ceiling and wall in some of the rooms. How can I fill them? There are also gaps between the baseboard and the wall, as if the wall is sort of undulating, and the straight baseboard cannot fit snugly against it. How can I fill those gaps as well?

J.S., Newton

A. Caulking compound will come to your rescue, although the gaps between baseboard and wall usually occur in old houses, not brand-new (a five-year-old house is virtually brand new) houses. Buy phenolic-vinyl caulking (Pheno-Seal and Polyseamseal are two widely available examples), and fill the gaps both at the ceiling and the baseboard. The caulking comes in a cartridge, so it is easy to extrude a small bead from a caulking gun. Then smooth out the bead with your fingers, and clean off residue with a wet sponge. This caulking can be painted, but not stained. And, it will expand and contract with the movement of the house, so it should stay in the gaps without breaking up, as a hardening wood filler will do.

Q. Can I use caulking between ceramic tiles instead of grout? 6. How can I hang things on a ceramic tile wall?

BEN SIMON, Somerville

A. Do not use caulking in the joints of ceramic tile. It won't work well, stays soft, and is virtually impossible to clean, and is simply not designed to go between tiles. Use grout instead; grout is a cementitious material (like concrete or mortar), and goes into tile joints very well. Most grout for wall tiles is sandless, making it easier to install. Sanded grout is usually used on ceramic tile floors. If you do intall new grout, the joint must be cleaned of all old grout, and the new installed very, very compactly; otherwise, it will fail.

Your question probably arose from the popular use of caulking (instead of grout) in the joint between tiles and tub. I feel that grout in this joint is better than caulking, even in these relatively large joints.

Q. I have never had any luck with caulking between the tub and tile. And in my present house, between the fiberglass tub surround and cast-iron tub. The caulking is quite dry now. I bought some silicone caulking. Will that improve things? I have also heard that filling the tub with water will depress it a little, allowing more caulking to go into the joint. Does that really help? Also, can I caulk the edges of a slider on the tub to stop a leak?

STEVE FUSI, Bedford

A. Most caulking jobs like yours fail because there is very little space for the caulking to go into. Caulking should go into a groove or a slot or trench, if you will; the same goes for putting mortar into a brick joint. Just slopping it on a plain corner is not going to work.

So, gouge out or remove the old caulking. And, filling the tub with water will indeed help depress the tub so there will be a good space for the caulking to go into. Fill the tub as high as it will go, take off shoes and socks, and get in the tub to depress it even further. When you get out and drain the tub, it will rise and tend to squeeze the caulking into a watertight joint. No kidding.

No, you cannot caulk against the slider; well, you can, but it won't do any good. You have to get the caulk into something. So, remove the frame, scrape off old caulk, and put a big bead of new caulk along the tub edge, then put the frame back, pressing against and squeezing the caulk. After the caulk sets, cut off any excess that is squeezed out with a utility knife.

Q. The silicone caulk on my tub, where the tub meets the tub surround, has turned black, and nothing seems to clean it up. Bleach does nothing. How can I clean it up and keep it clean?

SHIRLEY MOFFAT, Everett

A. Caulking is a modern way of filling such joints; someone got the brilliant idea of using caulking instead of grout, which is the ``old-fashioned'' way used years ago, and, frankly, grout is stil the better way to go. That black may be mildew, but it is in the caulking, not on top of it, so bleach does not lighten it. If the silicone is paintable, paint it with an oil-based, indoor-outdoor enamel.

If the joint is between tub and tile, you are better off taking that caulking out completely and inserting grout, which is like mortar, and the stuff that is between the tiles. It will fill the space neatly and if it gets dirty or mildewy, you can clean it with bleach. If the joint is between tub and a fiberglass or other non-tile surround, you have to stick with caulking.

Q. I took off my tub-shower slider, and the frame as well, leaving a lot of caulking on the edge of the tub and the face of the tiles. How can I remove it?

S.W., Wayland

A. If the tub is cast-iron, you can scrape off the caulking, carefully, with a putty knife or chisel; it also can be scraped off the tile. Just be careful that you don't scratch the tub or tile. To remove residue, apply acetone and wipe off with a coarse cloth.