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



Hello List!

Thought I'd toss in the 2 cents of a reformed, long-time user of 50/50
portland lime plasters...

The mix works well in that ratio, and like Tim I'd recommend hemp fibre or
ground hemp as the binder rather than straw. Works better and lasts
longer. The straw won't be a pretty colour, though.

Regular cement pigments work well in that mix too, although the lime will
tend to bleach them out and make them quite light. Darker tones benefit
from a painting or sponging of a wash of the same mix while the plaster is
still a bit damp.

Chris

> Hi All,
>
> Great comments.
>
> In lime/cement (which we are only using when we have extreme structural
> requirements due to unconventional design) we have avoided using soil as a
> pigment especially if the desired color is on the darker side of the
> moon...
> The lime is just too strong in whiting/bleaching and gets structurally
> compromised by the volume of soil or pigment added.
>
> Our most successful versions of what I assume you are going for are either
> structurally tested (in our shop first then at a lab we're seeing 800-2000
> psi) cement stabilized earth, called PISE' by some ... and also by fresco
> applied modeled pigment.
>
> We also prefer to use hemp fibre in our limes. You need less of it to
> minimize cracking and we only have 8 years experience with rice fiber
> degrading/graying minimally which is still too short to say its going to
> stay that way long term.
>
> Also John is right in pointing out that even a perfect color match in lime
> cement doesn't pass for an earth plaster.
>
> Best of luck,
>
> Tim
>
>
> Tim Owen-Kennedy
> Vital Systems Natural Building & Design, Inc.
> PO Box 751,  Ukiah, CA  95482
> 707.468.7488  707.462.3765
> www.vitalsystems.net
> 888.859.6336
>
>
> -----Original Message-----
> From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of Jeff Ruppert
> Sent: Wednesday, June 29, 2005 7:05 AM
> To: GSBN
> Subject: 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.
> Principal
>
> 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
> jeff@...
> www.odiseanet.com
>
>
> MattsMyhrman@...:
>> 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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