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Handyman Q&A

Various Sandpaper Grades Meant for Different Tasks


Question: What do "grade of abrasive paper" and "raising the grain" mean?

Answer: The "grade" (or grit) of abrasive paper (sandpaper) refers to the size of the abrasive particles in the sandpaper. Given the same number of passes and the same amount of pressure, paper with larger particles sands deeper (and rougher) than paper with smaller ones.

A lower number indicates that the grade of the paper is used for rough sanding; a high number indicates the sandpaper is meant for finish sanding.

Generally speaking, 30-grit and 60-grit papers are used for rough sanding, 100-grit to 150-grit sandpaper is for medium sanding, and 220-grit sandpaper is used for finish sanding.

Of course, this changes with the type of wood and whether the sanding is done by hand or with a machine. Sanding a soft wood with rough sandpaper could possibly tear the wood fibers (the grain). Sanding perpendicular to the wood fibers also could easily tear them. When the fibers tear, they raise from the surface. Another way of causing the grain to raise is to over-wet wood.

The best way to determine what grit to use is to test-sand. Keep in mind that rough grits of sandpaper leave deep scratches, so start with the finer grits (150 to 220) and slowly work up to the rougher grades.

Raising the grain is what painters must contend with after the first coat of paint is applied. At this point, and once the paint or varnish has dried, the first coat and the raised surface must be smoothed. The second coat of finish usually will not raise the grain. This is because the wood is protected from absorbing moisture by the previous coat.

Remove Peeling Paint With a Pressure Washer

Q: The paint on the outside of my house is peeling. What is the best way to remove it before I put on a new coat of paint?

A: Paint removal by a do-it-yourselfer is most easily accomplished with a pressure washer.

Although pressure washers are available for rent, if you are a homeowner we suggest you seriously consider buying one. The uses around the house are endless. But you need to be careful. If you aren't, you could damage the siding below. Pressure-washing takes patience, attention to the matter at hand and a careful touch.

Once you have finished pressure-washing, you might want to touch things up with a paint scraper. Also, sand areas where the pressure washer lifted the wood grain.

Next, use sandpaper to feather in all the edges between the remaining paint and any bare wood.

Finally, apply a coat of high-quality oil-based primer and then your finish coat. We suggest high-quality acrylic latex.

Have a Professional Test for Radon Gas

Q: I have cracks in my concrete basement floor from which I believe radon gas is creeping in. What is the best way to seal those cracks?

A: Before you do anything about that cracked floor, test for radon. Better yet, have a professional make the test for you. Another reason for contacting a professional: You might need to install a system to exhaust the vapors if radon is present in a dangerous concentration. The concentration of radon should be checked both before and after the concrete is sealed.

Sealing the cracks in the floor of your basement might be all that you need to do. Then again, perhaps more work will be needed. We hope you will not have to install the exhaust system we mentioned.

In any event, use a polyurethane concrete caulk. You are dealing with simple, old-fashioned gas vapors. There doesn't seem to be much pressure associated with radon vapors, so most concrete caulks will do. We have recommended the type that bonds the best and that holds up the longest.

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