Clay v. Lime
|Wheat paste applied to walls|
A fibre needs to be used in the plaster which you must test before using. Alex used cattails found by the side of the road.
In hindsight, I would have used lime plaster throughout the living space and kitchen so that I could have done tadelakt in the kitchen (more on tadelakt below), while keeping the colour consistent throughout. Lime is naturally very mold-resistant though still requires a textured substrate (wheat paste or mesh?) (Lime plaster would have also been a lot whiter.)
Problems with Plaster over MgO Board
|Crack above stove where we re-taped and re-Murcoed|
Clay Paint over MgO Board
Clay paint does not adhere to MgO board at all! We tried various times with various primers and in different thicknesses and it cracked and flaked off each time.
Lime paint/lime wash also does not adhere to MgO board. It has flaked off in every consistency. Whether there is a trick to getting clay paint or lime paint to adhere to the wall I don't know what it is.
Problems with Wood Next to Plaster
Another challenge was that the hemp oil on the wood window/door frames seeped into the plaster slightly even though the wood had been oiled months before, was oiled before it was nailed to the wall, and seemed totally dry at the time we plastered. It is not a huge deal but I imagine if we had not waited so long for the oil to dry it would have been a much bigger problem.
Burnishing and Tadelakt Finishes
|my finished kitchen|
I wanted to tadelakt the backsplash of my kitchen, but since we used clay in the living space and could not match the lime plaster to the clay plaster colour, I ended up using clay plaster in the kitchen.
Alex plastered my kitchen (pictured on left) and burnished the plaster, which smoothed it a little, but did not make a huge difference.
Sealing Clay Plaster: My Results from Testing VOC-Free Sealers
I tested three different sealers for the clay plaster in my kitchen, which needed to hold up as a backsplash around the stove and sink. From left to right I tested: beeswax, AFM Safecoat WaterShield (2g VOC/Litre) and AFM Safecoat Penetrating Water Stop (zero-VOC) (one and two coats), on burnished clay plaster. I splashed Worcestershire sauce on the samples, waited a few seconds and then wiped it off with a sponge. The Penetrating Waterstop was the only one that fully protected the plaster from the sauce. Two coats, however, turned white and blotchy. Note, the beeswax also changed the colour of the plaster a little yellow but it's not possible to see that in the picture. So, it was an easy decision since the AFM Penetrating Waterstop had no discernable chemical smell to me at all.
This has been holding up fairly well over the last couple years but when oil splashes onto it aroun the stove it does not wipe off easily. It is not the ideal backspash.