Liquid soap in the plastering/painting process

MzMolly65 said:

Tadelakt.

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I did not want to hijack MzMolly65's thread so I opened this one.

This is not a soap making post as much as it is a what you can do with your soap post. This is going to run a little long, but please bear with me.

We built an Earth-bag dome in the Philippines. It is coated with a basic lime plaster, (just slaked lime putty and sand). That plaster is lime washed.

This works extremely well as an interior/exterior coating. Brilliant white to reflect heat. It is vapor permissive, (it breathes), and semi absorptive while being water proof because of the walls overall thickness. For a few days after a rain the entire surface of the dome acts as an swamp cooler as the moisture evaporates out. We have measured up to a 20 degree difference between indoors and out because of this effect. We live in the tropics down on the equator and do not need air-conditioning.

This coating is very cheap, about 10 dollars will make enough white wash to coat the interior and exterior of a sizeable house. Very eco-friendly. The lime that flakes off we gather and spread on our garden and crop lands. Very easy to use. Clean up is a breeze. Just let it dry and wipe or sweep it up. No more drop cloths or paint thinner.

Problem is that lime is not very flexible. So after it sets it cracks easily. Then flakes off. A complete coating lasts about a year or so under our environmental conditions.

I read several recipes from England, Wales, and New England where people were slaking their lime with tallow or lard. Lime is a lower order alkaline than NaOH or KOH, but I suspect that there is a little saponification taking place in those old time light house whitewash recipes.

[ame]https://www.youtube.com/watch?v=_vl7hdqEeFs[/ame]

As an experiment I made up a batch of 100% Coconut oil soap. 0 % super fat. I then mixed the liquid soap into our whitewash. I was hoping that the soap would make a more pliable lime wash.

We applied the resulting mix to the interior of one of our bedrooms, and a small section of the exterior. It spread really well, filled all of the old cracks nicely, and dried evenly.

Problem is that when we tried to apply a second coat we could not. It was like the wall was electro-statically charged! Any liquid we applied JUMPED off of the coating and ran down the wall. We could not get anything to adhere to the treated area.

I tried to scrape it off and could not. I tried sanding it off. Apparently the Coconut whitewash penetrated the lower substrates as well.

I finally made up a very weak mix of Hydrochloric acid in water and applied that to the bedroom walls. That appeared to break down whatever chemical effect was happening.

I left the exterior test plot alone to measure the lifespan. It has been 6 months now and is still going strong. We spray it with a hose every day or so just to watch the water dance.

The Coconut whitewash section has cracked in a few places, so it is not as flexible as I hoped it would be. But it sure is hydrophobic.

How interesting! Thanks for describing your experiences.

It reminds me of lime-ash (like they used in England for walls and flooring from the late Middle Ages [see Little Moreton Hall]).

I like the waterproofing properties - I'm adding your experiment to my list of things to try (I've used beeswax for cloth waterproofing, but there'll be applications for a stiff waterproofing - thanks!).