Our car has dripped grease or oil onto the garage floor. How do you clean it? -- M.D.M.
For grease and oil stains on concrete, we recommend that you first scrub the stains with paint thinner or grease solvent.
Then mix one part sodium citrate to six parts of water and six parts of commercial glycerin. Add sufficient whiting powder to form a thick paste. Keep a coat of this paste on the stain for one week and add a new paste when the first one dries out.
Then flush the dried-out second layer away and the stain should be gone.
For rust stains on concrete, use the same mixture, but if the stain remains, make another paste of one part sodium citrate crystals to six parts of water and add sufficient powdered whiting.
Heavy layers of this spread dried on the rust stain will usually remove it. After cleaning, the treated area may look lighter than the surrounding concrete. This solution has a tendency to bleach the concrete.
It is a good idea to seal the concrete once it has been cleaned and is free of stains. Use a good masonry sealer, which is available from masonry supply stores, or use Thompson's Water Seal.
Another method of cleaning concrete supplied by a reader uses trisodium phosphate (an excellent cleaning agent).
First pour boiling water over the area to be treated. Leave just enough moisture on the surface to absorb the trisodium phosphate when sprinkled generously on the surface.
Use a stiff-bristled broom to scrub the mixture vigorously. Let this dry on the surface. Then hose down the area treated, again leaving just enough moisture to absorb dry portland cement when sprinkled over the dampened area.
Use a push broom to again scrub the area with this mixture, then allow to stand two to three hours. In this formula, the trisodium phosphate helps to remove the oil and grease stains, and the portland cement penetrates the pores in the concrete, leaving the appearance of a freshly laid driveway. When I moved into my 65-year-old house, I had the carpet removed and the oak floors refinished with a polyurethane finish coat. Now, 15 years later, there is wear in a few of the heaviest traffic areas. The flooring contractors tell me I cannot spot refinish the wear areas, but must move my furniture out and sand and refinish the whole floor. Is there an alternative? -- E.G. I agree with the contractors. To obtain a uniform, lasting finish the entire floor should be redone.
The existing polyurethane finish should be stripped, and the floors sanded prior to the application of a new finish.
If you opt to repeat the polyurethane finish, have several coats applied for lasting protection.
In the future, have a new polyurethane coat added over existing coats when the floor begins to dull, but before actual finish is worn through. This will give you added years of wear without an entire refinishing. We have a problem with bees forming a hive between the shingles and the wall on the side of the house. What can we do? -- E.M. Leave this problem to professional bee keepers or pest exterminators. It takes an expert to effectively remove a hive and prevent the return of another swarm. Send inquiries to Here's How, Copley News Service, P.O. Box 190, San Diego, Calif. 92112-0190. Only questions of general interest can be answered in the column.