What kind of plaster repair materials should I use?

Lesson 3

Now we will discuss the right kind of plaster repair materials to use.

A plasterer will use plaster compounds to repair plaster.  That's okay for the professional who understands plaster and knows the right way to use it.

But for our purposes, using drywall finishing materials  is much easier.  They are readily available and "mistakes" can be fairly easily corrected.  Dried drywall compound can be wetted and scraped off and the area redone if necessary.  So drywall joint muds are more forgiving for the novice plaster repair person.

Drywall muds come in many flavors.  What I recommend is the all-purpose (also known as multi-purpose) joint compounds.  All-purpose means it can be used to stick down the tape, overcoat the tape and with thinning can even be used to apply texture with.  So it is versatile.

Avoid "topping" compounds.  You don't really need them, and they are only good for topping applications, not taping.

All purpose muds come in full strength and in lightweight versions.  You can use either one, although I like the full strength varieties more, since they are tougher.  Just a little harder to sand when dry.

There is also "hot mud," special quick-setting joint compounds.  These have special advantages, but also some limitations.  I'll talk about those in another lesson.

One last note.  Plaster of paris (sometimes called patching plaster) can be used to fill deep divots in plaster.  It also works when small holes up to two or three inches wide appear in old plaster where the wood lath is exposed.  If you choose to use it for these situations, just be sure to dampen the wood lath first. And when the patching plaster is hard, wipe off the excess right away  that may have spilled over onto the painted area surrounding the patch.

Plaster of paris sets up FAST, so mix small amounts and use it immediately.

If you can a hairline crack around the perimeter of the patch after the plaster of paris sets up,
just fill that afterwords with your finger tip.  Wipe clean and smooth.
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Next time, we will explore the right way to fill in large holes in old plaster where the wood lath is showing behind, avoiding common mistakes often made in this kind of plaster patching problem.