[Cob] Re: powdery walls, was Sorry Jon...

[Patrick Newberry]

<snip>
When hydrated lime is added to water and applied to a surface as a 
limewash, the resultant finish gradually recombines with free carbon 
dioxide (CaO2) in the atmosphere and becomes calcium carbonate once 
more.  At this point your lime plaster has returned to its original 
state, limestone!
</snip>


Ok here is my question. I use hydrated lime form my feed store. I make a
white wash (basically) and paint on three or so layers. This first layer
mixes with the cob and with my georgia red clay makes a quite nice
looking color. After it drys, I put on a layer or two more and by then
the wall is quite white. 

This occurred in the last couple of months. At this point if I run my
finger over the wall you will see a bit, not a lot, of white powder on
one's finger. Over time due to the actions mentioned above will this
stop? It sounds like the fresher the lime, the less likey it would be to
stay powdery after being applied.

I've experimented with adding a bit of plaster of paris with the lime
thinking it might make it less powdery. Of that I am not sure, but I am
sure it makes the setting time much faster!

Other additives for strength, etc ?


Pat Newberry
www.gypsfarm.com