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How To Repair Plaster Article
17. How to Repair Plaster
from:Plaster is a centuries old product, mostly a mixture of fine limestone, or gypsum particles, and water. There are surviving examples found in ancient Egyptian ruins. It's funny, because it also was used in ancient buildings in the western hemisphere. Repairing really ancient plaster is not an easy DIY project. Specific mixes are required. So, some plaster jobs are best left to the pros. However, anything done in the past 200 years or so can be attempted as a DIY project. Why? Because plaster mixes have become a mass produced product.
In older homes, plaster was applied to a wooden lattice attached to wall studs, and ceiling joists. In newer applications, a type of chicken wire mesh is used. in either case it is important not to disturb this "base". If you find rotten lattice when you open up the plaster, you've got a big problem. The lattice may not hold your repair. You may be looking at replacing the entire wall. That's another topic entirely.
Ok, you've got a crack in your plaster. You will need the following tools, and products. A hammer, and good sharp chisel. The wider the chisel head, the better. A bucket of as hot water, as hot as your hands can stand. Do use plastic gloves, NOT latex, as latex absorbs heat. You also need a good pencil. Lastly a good sized sponge. Do put down some plastic sheeting to protect the floor.
Draw a line on each side of your crack, one inch away on each side. Dip the sponge in the hot water, and begin to apply it to the area. Do this one small area at a time, because a big area will dry before you are ready to open it. When the plaster begins to feel "wet" to your touch, and I mean plaster residue transfer to your fingers like flour does, you are ready to open up the area.
Place your chisel on the line you drew. Do this at a beveling angle. Forty-five degrees is good.
Tap the chisel with the hammer. You will learn very quickly how hard to tap. Do this one each side of the crack working your way down. You may need to tap the bottom of the wetted area as well. Be gentle, so you do not cut into the lattice. Repeat this process of wetting, then cutting, until you have the entire crack opened up.
Now you are ready to fill. You will need a trowel made for plaster, although a spackling knife can be used. Make sure it is a bit wider than your opening. You can buy "premixed" plaster products at any good store like Home Depot. It may cost a bit more than "U-mix," but I recommend the pre-mix because the consistency of the mix is better. Just be sure you tell your salesperson you are doing plaster, not drywall.
Dip your trowel, or knife into the mix. Get enough on there to cover the width of the blade. Cover the blade with mix, perhaps 2 inches up the blade.
Using steady firm strokes, begin to put it into your opened area. Work your way down the opened area.
When it begins to harden a bit, use a very light touch, and blend your mix to the old wall area. I call it "feathering."
Now keep the room nice and warm, and let your patch dry thoroughly before you apply paint. Some will say 14 hours, but I prefer 48.
Good luck on your plaster repair project