Today we spent the afternoon playing in mud, resurfacing the walls of our future bedroom with all-purpose drywall joint compound—aka sheetrock mud—to prepare them for a smooth topcoat of fresh gypsum plaster.
We love old imperfect plaster walls, but most of ours were cracking, the paint was severely alligatoring, and very little of the original veneer plaster remained if ever there was any. (On this alligatoring paint sits one of the many ladybugs infesting this room. They’ll have to move on by the time we move in, but for now we love their company. I’ll write more on this subject once it’s time to shoo them away—reportedly no easy task.)
I've recently learned that until the 1930s, most walls in this country were built up from two or three layers of plaster, made from lime rather than gypsum, which supplanted lime in the early 20th century because it cured almost instantly and dried in two to three weeks—compared to the 12 months it took for lime plaster to dry fully. The first two coats of lime plaster were coarsely textured, to build volume and strength. The base layer, or “scratch coat,” contained animal hair.
The plasterer usually applied it to lath—a sort of wood trellis through which the plaster extruded and created “keys” to lock itself into place behind the support. The plasterer roughed up, or “scratched” this first layer, to enable the next layer to lock itself in place as well. That second layer, called the brown coat, contained coarse sand. Finer plastering jobs included a third, thin lime topcoat without any coarse stuff, making for a smooth finish. But Kevin, who has always seemed to know about these things, hasn’t come across this third layer on our walls, meaning the plasterer stopped at the second layer of browncoat and sanded it.
A two-layer plaster job would not have been unusual for an old farmhouse, which probably had papered walls according to Historic New England. (Alas, we found no evidence of the original paper—just a few layers of paint and some paper from the 1950s in the parlor.) I can’t imagine living with all that pattern, so while we may paper the hallway, as a passageway where we’ll never sit staring at the walls, we’ll paint the other rooms.
Kevin drew this diagram in the mud to illustrate our mission today, which is a modern twist on the old techniques: that undulating bottom layer is our original wall (or what was left of it).
The next stratum is the new mud, striated with this serrated trowel in the most uneven areas, to create the lowest but grippiest possible base for the topcoat of plaster, sort of like the scratch coat in historic plastering jobs. Before we paint, Kevin will artfully apply a smooth mix of mud and gypsum plaster as a topcoat.
I’ve watched Kevin mud and replaster walls over the years, and he makes it look simple—and as fun as painting. Today was my first time out, and I did find it fun to scoop out the mud, sling it on the wall, and smear it around. But it was utterly frustrating to smooth it out and finish it—primarily because it will never be perfectly even. That’s what sheetrock is for, and we don’t like that glass-perfect surface on interior walls, let alone historic ones; we want old-fashioned evidence of the human touch.
Kevin says for this base layer it’s a matter of learning what’s smooth enough—reminding me of my mother’s line about making her beautifully flaky and delicate pie crusts. Whenever I ask her how she knows when to stop cutting the dough, she says, “You just have to do it enough times to get the feel of it. Then you know.” Consequently, I don't do crusts.
Kevin is more like my mother than I am in his mastery of domestic arts. He has certainly mastered the art of mudding and plastering; I’ve watched his process and seen the finished product enough times to trust his judgment. He says I’m doing fine. I’ll believe him and muddle along to lend him a hand until I know—knowing he’s just a few paces behind me with his trowel.