If you are one of the many men who have had disappointing results in painting cement floors in a basement workshop, recreation room, sun porch or elsewhere, you may be skeptical about the durability of floor, porch and deck enamel on concrete surfaces. Actually, any first-class enamel
made for this purpose will give satisfactory results if correctly used and, still more important, if the cement is properly prepared for painting.
Dampness is always the enemy of paint. When a cement floor shows evidences of dampness during certain periods of the
year, you can save yourself a lot of trouble by giving up the idea of painting it with floor enamel. Even some floors that appear reasonably dry are unfit to paint. Here is a simple test: Find a scrap piece of linoleum and lay it down in some out-of-the-way corner of the floor. After a few days, lift it up and see if the floor beneath shows any signs of dampness. If not, painting can probably be undertaken with reasonable assurance of success.
If the floor had been previously painted, you will next have to decide whether or not to remove the old floor paint. If it is in bad condition, it is best to remove it. This may be done inexpensively by using a strong alkali solution. One pound of lye dissolved in five pints of water will make such a solution, but it should be used with caution. Wear old clothes or overalls, protect your hands with rubber gloves and your shoes with old rubbers, and be careful about splashing the alkali around. If
any gets on your skin, wash it off immediately with cold water.
Use a stiff fiber brush to apply the solution and when the paint has been removed, wash the surface with clean water. It is important to flush away every trace of the alkali. The floor must then, of course, be allowed to dry thoroughly. The next question—and this applies to a floor treated as has just been described as well as a cement floor which has never been painted—is whether or not to etch
the surface with acid. Paint experts recommend the etching of all cement floors prior to finishing, although satisfactory results are frequently obtained without going to this trouble. The advantage of etching is that the enamel will adhere much better; besides, the acid neutralizes all traces of alkali, which react on paint.
Etching is usually done with a ten per cent solution of muriatic acid. This is prepared by diluting one part of commercial muriatic acid with three parts of water in a wooden bucket or enameled pail. Add
the acid to the water. Never pour water into acid. The acid will attack a galvanized-iron or other metal pail. About one gallon of this solution is sufficient to etch 100 square feet of floor area. The
same precautions must be observed as those mentioned in connection with handling the strong lye solution. These are very important because the acid can be dangerous if carelessly used. Adequate ventilation also should be maintained.
Apply the acid solution with a stiff fiber brush. Wait until the acid stops bubbling on the floor and rinse it off completely with clean water. Note how quickly the surface dries. If it is still damp three or four hours later, wash it again with water and let it dry thoroughly.
The floor enamel, which should be of a type recommended for cement floors by the manufacturer, should be applied according to the directions on the can. These may vary slightly according to
the product, but as a rule the first coat is thinned with a little turpentine—not more than one pint to a
gallon of enamel. The second and third coats are not thinned.
When repainting old work, it is best to touch up any bare or worn spots with slightly thinned enamel and let them dry, after which one or two coats of the full-bodied enamel may be applied.