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Re: GSBN:Re: Half lime, half cement plaster mix

We have used integral pigment with both pure lime and lime/cement.  The
main thing to look out for is adding too much pigment.  If you are
trying to get a dark, rich color, adding lots of pigment will interfere
with the chemical reaction of the lime and/or cement and weaken it.  If
we are going for a dark color, we apply the pigment by sponge after we
apply the final coat, while it is still wet, and then also paint the
pigment on the next day.  It is a two step process.

If you are concerned about adding too much pigment, you can talk to the
pigment supplier, or even a concrete batch plant operator.  They are
aware of these issues.  They sell pigments and there are specific
maximum ratios of each due to their densities and contents.

Jeff Ruppert, P.E.

Odisea LLC
Ecological Building, Engineering and Consulting

Front Range Office 		West Slope Office
5444 Marshall Road		1022 Main St.
Boulder, CO  80305		Carbondale, CO 81623
303.443.4335			970.948.5744
303.443.4355 f			1.866.795.6699 f

Dear GSBN-ers,

Some friends of mine are considering using the above ratio of lime and cement
in their plaster.  They recently asked if I knew of any good reason why they
couldn't successfully use standard, commercial plaster pigments to get a color
like mud plaster in the final layer (aka, color coat).  I told them I had
never used pigments in such a mix, but if the pigments consist of various oxides
of iron, I didn't think that the higher-than-usual amount of lime in the mix
would cause any problems.  If any of you have reason to think that this was not
a good answer, I'd sure appreciate hearing from you.

Also, they asked the same question about adding chopped straw to their mix,
in order to get a rustic texture.  I told them that I had only used chopped
straw in mud plasters and in mud/lime plasters, but that I thought that it would
also work fine in the  half lime/half cement mix, assuming that they didn't
add so much that it significantly weakened the plaster .  Again, if you think my
answer needs adjustment, please share your thoughts.

All best wishes to you all from Judy and myself.

Matts Myhrman / Judy Knox                        mattsmyhrman@...
Out On  Bale, (un) Ltd.
1037 E. Linden                                           judyknox42@...
Tucson, AZ  85719
Office message phone  (520) 622-6896

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