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Re: GSBN:Re: Lime plaster problems

Hello Bill,

I am very interested by mr Francis paper. If you mind forwarding it to me, I
would appreciate.

Best regards to you and Athena,

Michel Bergeron
6282, de Saint-Vallier
Montr?al. Qu?.
H2S 2P5
(514) 271-8684

Le 07/10/07 12:00, ÇÊAthena & Bill SteenÊÈ absteen@... a ?critÊ:

> I'll plead busy as well and before I made any comments I wanted to
> make sure they would be somewhat thorough.  There are a few things
> that have become evident to me over the years when it comes to lime
> over clay plaster.  In mho I would have to say that results are
> unpredictable and undependable.  I'm not saying it can't or doesn't
> work, but rather that outcomes vary widely. David Bainbridge
> mentioned in his earlier post the Getty people in Los Angeles as a
> resource.  I've made it a point to talk with them every few years
> about lime plaster and in particular their work with prickly pear
> cactus gel.  Anyhow in one of the last conversations we had they told
> me that there was a growing sentiment amidst the conservation
> community that the use of lime plaster over earth surfaces was not
> such a good idea.  They mentioned that although lime had better
> permeability than cement and allowed the earth to dry better when
> wet, it was still too different from an earthen substrate for it to
> work dependably.
> My experience basically says the same thing.  For me the whole issue
> comes down to what type of earth plaster is underneath.  Apparently
> some are much better than others and just what all the variables are
> I can't say.  I think it will take some time to get a better grasp on
> it.  Clearly I would suggest that if the substrate has a lot of clay
> there is a likely possibility that if water is absorbed through the
> lime plaster and passed on to the earth substrate then obviously the
> clay will expand and have a tendency to push the lime plaster away
> therefore causing the two to separate.  If the earth plaster is weak
> then the connection will break down over time.  So in short I guess
> what I'm saying is that the earth plaster has to be of a really good
> quality for any chance of success.  It needs to be strong and not
> have an overly high content of expansive clay.  Another very
> important piece is that the earthen plaster substrate must be
> thoroughly dry as earth plasters shrink when drying. If that process
> is not complete the earth will pull away from the lime plaster and
> leave it hanging in the air. And as others have pointed out the
> surface needs to be extremely well keyed for the lime to adhere.  I
> don't think you can under-do that aspect.  Additional measures like
> that of placing sharp jagged stones in the plaster would also help
> such as the practice of "rahuela" used in Mexico where stones are
> placed in the mortar joint between adobes.
> I think it was David that also mentioned the Japanesete We have
> worked closely with a pair of Japanese plasterers over recent years
> and it is important to note that the Japanese approach relies heavily
> on use of a glue when mixing what they call "Shikkui." Traditionally
> rice flour was used but was replaced with seaweed gel during a time
> of food shortages.  In general I would say that their plastering
> practices are far more meticulous than anything I've seen in this
> part of the world and in the words of the best plasterer from there
> that I can think of, "there is great difficulty in the connection
> between the two coats and at best it does not last for a very long
> time."
> Having said all this I will say that my comments apply primarily to
> exterior finishes and I've not yet experienced any problems with
> interior or protected locations.  But I should add that we also
> typically include a percentage of some glue material in the lime
> plaster.
> John Glassford suggested the use of lime/clay as an alternative and I
> think that it can be a very good one.  Much here depends upon the
> reaction between the clay soil and the lime. Over the years I've
> watched varying reactions, some soils produce exceptional results,
> others marginal.  I recently cornered Harry Francis who once worked
> for the American Lime Association while we happened to be together
> recently in Washington DC.  I told him that the using pH as an
> indicator of the right type of mix was not proving true all of the
> time.  Like he always does Harry went home and searched his extensive
> resources and just emailed me a paper that addresses some of those
> variables particularly soils with high levels of potassium and sodium
> carbonates.  I haven't had time to really absorb the content, but if
> any of you want a copy I would be happy to forward it.
> I've already said more than I had intended, but to sum it up I would
> not suggest that we recommend the use of lime plaster over earthen
> substrates as a general practice.  I would suggest that it be adopted
> only after some testing and experimentation has been done and with a
> warning that the results are always guaranteed.
> Bill
> On Oct 7, 2007, at 7:10 AM, Rikki Nitzkin wrote:
>> Sorry to chime in so late...been busy. Its just that I haven't seen
>> anywhere
>> that in the responses to remind Andy that it is very important to
>> wet down
>> as well as scratch the base layer of plaster before applying a new
>> coat, and
>> if the material is different (lime on clay in this case) really rub
>> the
>> first bit in so it binds well.
>> Hope your problem has been solved.
>> Rikki Nitzkin
>> Aul?s, Lleida, Espa?a
>> rikkinitzkin@...
>> (0034)657 33 51 62
>> www.casasdepaja.com (Red de Construcci?n con Balas de Paja)
>>> -----Mensaje original-----
>>> De: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] En nombre de Brian
>>> Hodge -
>>> Anvill
>>> Enviado el: jueves, 27 de septiembre de 2007 22:20
>>> Para: 'GSBN'
>>> Asunto: RE: GSBN:Re: Lime plaster problems
>>> Hi Andy,
>>> I agree with John. We have been doing a very similar thing for
>>> about 5
>>> years and have not found it necessary to add the lime putty top
>>> coat. We
>>> have even done it without chaff with a great deal of success.
>>> Regards
>>> Brian
>>> Anvil Straw
>>> -----Original Message-----
>>> From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of John
>>> Glassford
>>> Sent: Thursday, 27 September 2007 7:53 AM
>>> To: GSBN
>>> Cc: Andy Horn
>>> Subject: Re: GSBN:Re: Lime plaster problems
>>> G ' day Andy
>>> My two rands worth mate.
>>> You will need to remove the lime coat and scratch up the earth as
>>> others
>>> have said.
>>> I would then apply a mix of earth/lime/sand and chaff or chopped
>>> straw.
>>> All depends on the clay content of your earth but I would look at
>>> something like this 3 parts soil 2 parts lime 3 parts sand 1 part
>>> chaff.
>>> I use buckets for this mix.  It works well and binds well with the
>>> earthen render.  Then if you want you can apply a finish coat of lime
>>> render however I have not found that necessary in most cases
>>> except for
>>> look.
>>> You can see a house we renedered with earth, then earth/lime/sand/
>>> chaff,
>>> then lime/sand, here:
>>> <a  target="_blank" href="http://glassford.com.au/Jumbo.htm";>http://glassford.com.au/Jumbo.htm</a>
>>> No delamination no cracks and it is nearly 6 years since we finished
>>> there.
>>> Was in Cape Town a few weeks ago but did not have time to see much it
>>> was a Rotary trip with Hout Bay.  We will be back next year for an
>>> extended visit, see you then.
>>> Kind regards
>>> The Straw Wolf
>>> Huff 'n' Puff Constructions
>>> <a  target="_blank" href="http://www.glassford.com.au/";>http://www.glassford.com.au/</a>
>>> 61 2 6927 6027
>>> Mount Kilimanjaro Climb 28/8/07 <a  target="_blank" href="http://www.coolamonrotary.com/kili/";>http://www.coolamonrotary.com/kili/</a>
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> Athena &amp; Bill Steen
> The Canelo Project
> HC1 Box 324
> Canelo/Elgin, AZ 85611
> absteen@...
> www.caneloproject.com
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