[Cob] Limewash/Whitewash and other permeable paint options

[Henry Raduazo]

Simon:
1. regarding using lime and sand, I only followed the recipe from a  
plaster book, I needed to fill in a little from the manure/clay and I  
too wanted to cover the very dark base coat.
2. Lime should not rub off on your hand after it has hardened. Mine  
does not rub off on a wet sponge.
3. I am a little concerned about lime from a hardware store. As I  
said, I bought my lime from a place that sells nothing but bricks,  
sand, mortar and other masonry supplies. I even used the lime putty  
to lay the stone for my knee wall. It hardens like cement and you  
would not expect cement to rub off on your hands. After you apply the  
lime it absorbs CO2 from the air and becomes limestone. Limestone  
does not rub off on your hand. I would say something is not right  
with your lime.
	Were the bags of lime sitting next to the cement and bricks in the  
hardware store or did you find it in the garden department? I don't  
trust the people in hardware stores to know anything about anything.
Ed
	
On Mar 7, 2009, at 8:14 AM, Simon Matthews wrote:

> Thanks for your reply
>
> On Fri, 2009-03-06 at 20:25 -0500, Henry Raduazo wrote:
>> Simon: I did two layers of horse manure and clay on my wall, then a
>> thin layer of lime putty (2 parts sand one part lime) then two coats
>> of lime wash. I sprayed water on the lime layers three times a day
>> with a 2 gallon insecticide sprayer.
>
> I am interested to know why you made the last plaster coat with  
> lime and
> sand. Was it to provide a good base for the whitewash?
>
> We are lucky in that one part clay/subsoil from our property with two
> parts river sand produces a render that doesn't crack and feels very
> solid, rather like a cement render. The one problem with it is that it
> is dark chocolate brown which i would think will take many coats of
> whitewash to cover. I was thinking of doing a plaster coat purely to
> make a light base to put the whitewash on.
>
>>  You can't rub my lime off. I
>> don't even think you can sand it off, and I have not redone my wall
>> for ten years. It is an interior wall with out much rubbing, but that
>> would not matter.
>
> To date I have done a small test of three coats of whitewash  
> applied one
> day apart directly to the mud render making sure to keep the surface
> damp. Wiping a finger across this test sample will leave a thin  
> smear of
> lime on my finger but the coating remains intact. Is this normal?
>
>>  It has lots of impurities in it so it is not edible grade
>> but it is cheap. Just add water and use, or store in a sealed drywall
>> bucket covered with a layer of water. You should be able to make a
>> bench and sit on the bench with out getting powder on your clothing.
>> If your lime does not harden like, this it is no good.
>
> I noticed that the hardware store had two brands of hydrated lime for
> sale. I might try the other brand. I assume that if some of the  
> hydrated
> lime is calcium carbonate and not calcium hydroxide as it should be  
> that
> the calcium carbonate might not become part of the crystal  
> structure of
> the cured whitewash and this might be what is coming off on my finger.
>
> Simon
>
>