WALL SIZING FOR KALSOMINING.
There are many things about wall sizing, which depend largely upon good judgment for success, because the treatment must be varied according to the condition of the wall or ceiling. A good size is made of good white glue, ½ pound; alum, 1 pound.
Dissolve the glue in the usual way; that is, soak it in cold water until soft, then pour off the cold water and pour on the hot water; and stir until the glue is dissolved.
Dissolve the alum in hot water.
Then stir the glue, and put in the alum water. Thin the mixture with water to the right consistency to work well.
If one coat is not sufficient, give it two; or if there are porous places in the wall, touch them up.
In many cases a simple glue size is sufficient, but if you use the glue and alum size as above directed, you will be pretty sure of a good foundation for kalsomine.
One of the most difficult things to overcome in preparing ceilings for kalsomine is the water stain, which is liable to be invisible until developed by a coat of kalsomine. If you find water stains on a ceiling and suspect that there may be others which do not show, go over the ceiling with a thin wash of whiting mixed in clear water, which when dry will develop all hidden stains. To kill a bad stain, first put on a coat of oil, japan and turps, equal parts; second, put on a coat of good heavy shellac; third, give the spots a coat of flat lead. This treatment is for dark stains; for light stains a coat or two of shellac will stop the stain. It is best to put a coat of keg lead thinned with turps over the shellac, because kalsomine is liable to scale off from shellac.
On cheap work, if the stain is not too dark, it may be kept back by pasting a piece of paper over it. If the wall has been kalsomined it is always in order to wash off the old kalsomine. If the work has been whitewashed, either take it off or first give it a wash of strong vinegar, then a glue size, which, if put on thin and plentifully while warm in a warm room, is about the best size I know of for whitewash. I have often used it successfully when it was not practicable on account of the weakness of the ceiling or other cause to take off the old whitewash. Two thin coats of good glue size on firm whitewash makes as fair a foundation for kalsomine as can be made on old whitewash.
When it will not pay you to wash off the old kalsomine, a coat or two of the wall sizing described above will make a good foundation.