Do It Yourself: Best to start with clean joint when recaulking

Q. There are a couple of bathtubs in my house with old, dirty, cracked caulk around the joints. I want to replace the caulk, but the old stuff is so hard I haven’t been able to get it out. Can I put new caulk on top of the old? Also, what is the easiest way to caulk a tub? I’m a beginner.

A. You should not put new caulk over old. The old caulk should be removed and the joint cleaned in order to get a good seal for the new. There are a couple of ways to soften old, hard caulk so it can be scraped out. If you have porcelain tubs with ceramic tiles on the walls around them, you can use a heat gun to soften the caulk. Once softened, the caulk is fairly easy to dig out with a sharp tool.

I use a five-in-one tool, which has a sharp, wide blade with a hooked corner that can get into crevices. A screwdriver, wood chisel, putty knife and similar tools also work. You can buy a heat gun for about $25 on the Internet or at some home centers and hardware stores. I wouldn’t use heat if you have fiberglass tubs or wall surrounds, or if there are painted surfaces around the tubs (the heat needed to soften caulk might damage some materials and will cause paint to bubble and loosen).

Old caulk can also be softened with special solvents such as 3M Caulk Remover, which is supposed to soften any type of old caulk; it costs about $7 for a 10-ounce squeeze bottle. Some solvents will soften only latex caulk, others are for silicone caulk, so be sure and read the directions before buying.

The best tip I can offer occasional do-it-yourselfers when caulking a bathtub or sink is not to use a caulking gun equipped with a large cartridge of caulk. Instead, buy the caulk in toothpaste-type tubes. A typical tube costs about $4. It is much easier to get a smooth, even bead of caulk in the cramped space of many tubs by squeezing a small tube instead of trying to manipulate a heavy, long caulking gun. Both silicone and latex caulks are available in squeeze tubes.

For caulking a tub or sink, look for tub-and-tile caulk or kitchen-bath-plumbing caulk. Also make sure the caulk is mildew resistant. Silicone caulks are fully waterproof and some are ready for use faster than latex, but many do-it-yourselfers find them difficult to smooth. With latex, a wet fingertip will smooth the bead; silicone needs mineral spirits (paint thinner).

Another good tip is to fill the tub with water before caulking; this will approximate the weight of someone taking a bath and cause the tub to settle slightly. Without the weight, a filled tub might cause the caulk to pull away slightly when used. When caulking a tub-wall joint, it is also a good idea to caulk the joint of the tub with the floor, if the tub is the common walled type, the sink-wall joint, and the joint of the toilet and floor.

Q. I have several forsythia hedges that I trim twice a year. I have been using a gasoline-powered hedge trimmer, and it is a pain – heavy, hard to start and, I think, dangerous. I hate making the gas-oil mixture. I tried a corded electric trimmer but the cord keeps getting in the way. Are battery-powered hedge trimmers any good?

A. I’ve been using a battery-powered hedge trimmer for several years, trimming a variety of hedges and shrubs including big yews, and I like it for a number of reasons.

I have a Ryobi trimmer; one of the many One-Plus tools Ryobi has developed for use with 18-volt batteries. I use lithium batteries, but I previously used nickel-cadmium batteries with good results.

I have several batteries so I can always keep one well charged to take over if the one I’m using runs out of power. The Ryobi trimmer has an 18-inch blade, which will trim most hedges.

I have used both corded electric and gasoline trimmers in the past, and think the battery trimmer is safer than either and easier to handle.

I have found that other battery-powered lawn tools are also good performers, and use a battery string trimmer and blower. Both of these, plus several other tools, are Ryobi One-Plus and use the same batteries I use in the hedge trimmer.

The hedge trimmer costs about $100 with one lithium battery and a charger, or about $60 without batteries.