Over the years, a number of individuals who've read my books on natural building (The Natural House) and natural plasters (The Natural Plaster Book) have contacted me for advice on their projects. A few have grumbled about the the arduous task of making flour paste to add to their earthen plasters. Flour paste makes an excellent binding agent and is one of several additives my co-author Cedar Guelberth and I recommend be added to earthen plasters to produce a superior wall finish. Flour paste helps plaster adhere to earthen and straw bale walls and creates an amazingly hard plaster.
That said, I agree with those who find the process of making flour paste to be arduous and time consuming. It is a real pain in the neck. In fact, I stopped using it several years ago because it takes so much time and energy.
I achieve the same results now by adding low-fat powdered milk to my earthen plasters — both base coats and finish plasters. It's much faster and requires a lot less effort.
Here's what I do: First, for large projects, I buy large boxes of powdered milk. I mix it at half the recommended concentration for drinking. I use this dilute milk for all the water I need to make a plaster.
I have found that this works marvelously. Just don't let the plaster sit around wet for more than a day or two, as the milk will spoil and start to smell. Mix what you need and apply the plaster within a day or two of mixing. This will save you a lot of time and frustration. If you want to learn more about plastering, come join us at The Evergreen Institute in Missouri (www.evergreeninstitute.org). We're offering a course on natural plasters this summer (http://www.evergreeninstitute.org/intronaturalplaster.html).