Best Way to Clean Oil and Grease Off Concrete


QUESTION: What’s the best way to clean oil and grease from a concrete floor?

ANSWER: If oil has been freshly spilled onto a concrete surface, blot up as much as you can, then cover the spot with one of the following: powdered calcium carbonate, hydrated lime, talc or fuller’s earth. Portland cement can also be used. Let powder stand for 24 hours and then scrape it off.

If oil has penetrated into the concrete, scrape off whatever remains on the surface with a putty knife and then cover the stain with a stiff poultice made from one of the powdered substances above combined with a solution of 1 part trisodium phosphate and 6 parts water. Let the poultice stand 24 hours, then scrape it off. Scrub the surface with clean water.

Grease is easier to remove than oil. If scraping and scrubbing don’t work, use a poultice made from benzene, naphtha or trichloroethane and an inert powder. Allow it to stand 24 hours, then scrape the surface clean.

Covering Oil-Base Paint With Latex

Q: Please advise what to do with a building that has two coats of oil-base paint and needs painting. I would like to cover with a water-base paint. Is this possible? I intend to perform the work myself.


A: According to the technical department at Benjamin Moore Paint, there is nothing to prevent you from spreading latex over an oil-base paint. In fact, you can go back and forth between latex and oil.

However, the wall surfaces must be properly prepared. They must be clean, free of dirt and grease spots, and should not be excessively chalked. A good way to ensure proper surface preparation is to have the walls power washed. The wash water usually contains additives that will kill mildew. Priming the surface is not necessary if it is in good condition, with no peeling sections or blisters. If there are, those sections should be scraped and spot primed. You can then apply one coat of a good quality house paint, although two coats would be better. A good quality paint, applied correctly, should last six to seven years.

What Extinguisher Is Suitable for Home Use?

Q: I want to buy a fire extinguisher for my home, but I don’t know which type to get. What do you recommend?

A: The wrong type of fire extinguisher could do more harm than good. It must suit the type of fire that’s burning.

There are three types of fires. Class A fires are those that involve ordinary combustibles like wood, paper, cloth, rubber, etc. Home fires of this type often start in the living room or bedrooms. Class B fires involve cooking oils, grease, gasoline, paint thinners and other flammable liquids. These fires generally break out in kitchens and garages. Class C fires are electrical fires and are usually the result of faulty wiring, overloaded circuits or faulty electrical appliances.

On fire extinguishers, these categories are designated by the letters A, B and C within a triangle, square and circle, respectively. Class B- or BC-rated extinguishers are not effective on Class A fires. Also, water, which is effective in putting out a Class A fire, will cause a Class B fire to spread and can cause a severe shock in a Class C fire. Once a fire in the home spreads, it can quickly include all three categories. Therefore, your best choice is a fire extinguisher rated for all three classes of fire.

Fire extinguishers are available at hardware stores and home centers. When you buy one, check to see that it’s listed by Underwriters Laboratories Inc., and displays the A, B and C designations. Also, note the numbers in front of the A and B designations. These refer to the size of fire that the extinguisher can generally handle. The numbers are not absolute figures; they are relative terms for comparing different units. An extinguisher with a rating of 2A:40B:C will handle a Class A fire twice as large, and a Class B fire four times as large, as a unit rated 1A:10B:C.

Note that there are no size ratings for Class C fires. The C designation means only that the chemical inside will not conduct electricity.

Re-Tensioning Windows Is Open and Shut Case

Q: Our windows are fitted with spiral balances that seem to have lost some of their tension. Also, the windows do not operate as smoothly as they once did. What can I do to remedy these problems?

A: In time, the springs of spiral balances may weaken. Re-tension them by unhooking the spiral rods from the mounting plates, then turning the rods counterclockwise once or twice. The mechanism can be serviced by releasing the tension and unwinding the rods from the tubes. Wipe them clean and apply a little thin oil, then rewind the rods back into the tubes and tension them as described above.

Ways to Reduce Sound in Room Additions

Q: We are adding a new wing to our home, and the walls will be constructed with gypsum wallboard. What can we do to reduce sound transmission between rooms?

A: The conventional system of framing and finishing affords relatively low resistance to sound transmission. The typical wall, framed with 2-by-4s and finished with one-half-inch wallboard, has a sound transmission rating (STC) of only 30 to 34. Filling stud cavities with batt insulation and using thicker wallboard, even doubling the layers of wallboard, will improve the situation.

One of the most effective approaches to the problem, however, is to modify the wall framing method by using lumber for the top and toe plates that is wider than that used for the studs. Studs are then fastened in place on eight-inch centers, with edges alternately aligned with opposite edges of the plates. This reduces the amount of sound-induced vibration that is transmitted from one side of the wall to the other. The STC rating of a wall made of 2-by-4 studs set on 2-by-6 plates finished with double layers of five-eights-inch wallboard, is about 50 to 54--nearly equal to that of a seven-inch-thick brick cavity wall.