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Re: GSBN: Lime plaster problems



Hello, it has been very interesting catching up on the lime plaster on earth thread. Thanks everyone.

A French practice to increase adhesion of lime plaster on earthen plaster is to apply wet the earth plaster/wall with what we call 'strong water'. This is the water that floats above the quicklime (or a mix of 20 water for 1 lime).

By the way, all wattle and daub multi story houses I see in France have been lime plastered quite some time ago, probably by masons who knew their lime and their soil (all three local!). Though I hear what Bill's Japanese plaster master says about lime on earth. It does seem to stick for quite a while when done correctly.

I recently saw a lime wash over earth (not very common in France as far as I can tell) and was impressed how it greatly increased the strength of the plaster when I scratched it with a nail of my thumb . The same plaster without lime wash was easily destroyed with the same amount of pressure. This lead me to believe the mason who told me that the lime goes in quite deeply into the earth and is not only a coat on the surface. I quite liked the reply of that same mason when asked: "How long before a lime wash needs to be redone" His reply (with a slight grin) "that depends on the amount of weathering you can accept".

ah yes, on to Roman cement...   this is going to get good... come on you experts.
Limes vary in clay content (here she is again ;-). The more clay, the more hydraulic the lime is (meaning that the reaction is fast and set off by the water and less by the air). The old masons (and the young ones too) would add different types of additives. Not to get a better lime, but to adjust their (local) lime to the the way and place (plaster/foundation etc.) it was used. Hence, when it seems that some type of soils work better with lime than others, the same might be said for different type of limes. It is only since quite recently that we 'import' lime from other regions. Maybe local limes work (often) with local soil? (this is just an idea!)

The French book I'm reading at the moment goes on to say that only washed sand should be used because clay particles can be a disaster. But the oldies also mixed their lime with soil to obtain plaster. One sample of lime and soil I tested worked just fine with 1 lime for 3 (clay rich) soil but the same soil with only 10% lime turns to dust when one touches it. I now show this sample during workshops to make the participants realize that all this mixing of ingredients really is alchemy for beginners as I have no clue as to what type of clay(s?) are in my soil and only have a vague notion of how hydraulic a bag of lime is supposed to be. It' is more or less like, huh,... what would happen if I push this red button here... There's only one way to find out unless someone has done it before you have (and is still there to tell you).

I used to find all this lime in/on earth way to complicated for me and steered away from it. But the before mentioned mason showed me some very nice samples that have roused my interest. It must be a bit like women : I have no idea how they work, but that don't mean they don't.

André Test Test Test de Bouter












-----Original Message-----

From: Andy Horn To: 'GSBN'
Sent: Wed, Oct 10 4:40 PM

Subject: GSBN: Lime plaster problems





Interestingly the locals in Kokstad who build with adobe ...but don't add sand to help with cracking will search to find a much rarer creamy coloured clay that can be found in the area to do their plaster coat with....and will then typically apply a lime wash to finish with. However they have not learnt to add sand so the walls are usually quite crazed with cracks.....Sometimes they also add cow dung which helps somewhat with the cracking. Not sure if we can get any marble dust in that area,,,,but as I understand it you would want that in the earth plaster to get the bond to the lime coat...... Interestingly I hear from an archaeologist/conservator friend of mine that the Romans often used to add marble dust to their lime plaster. The other thing the Romans did was add fine fired brick or tile dust/powder to their mixes.....not sure what that was for or if it was simply instead of or when they ran short of sand??? Andy Horn -----Original Message----- From: GSBN [<a target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of Athena &amp; Bill Steen Sent: 08 October 2007 02:02 PM To: GSBN Subject: Re: GSBN:Re: Lime plaster problems Franko, I think a major plus in your area is the calcium component in the caliche soils. So therefore we have a chemical connection going on beside the mechanical. And that is what is basically lacking with most soils. One way to increase the possibility of a better chemical bond is to use marble aggregate instead of quartz sand. B... On Oct 7, 2007, at 2:50 PM, thangmaker@...: > Thank you, Bill. I have had good results and no problems to date > putting lime over earthen plaster made with our native caliche > clay. We have done what Bill > > > suggests: scratching the surface well and letting the earthen > plaster dry completely. For those unfamiliar with caliche it > occurs in the same soil as limestone. > > > It is the same basic material as lime (calcium carbonate) but less > dense and not well bonded to itself...flakey if you will. > Occasionally clay is found with this > > > material and is the best clay I have seen in terms of PI index (low > expansion and contraction). This is the clay I wanted to use for > the fire test last year in San Antonio but as Matts pointed out it > would not perform well in a hot fire. I am guessing the material > is similar enough to lime plaster that it both bonds well to it and > their rate of movment and reaction to moisture is similar. > > > > > > Cheers > > > Frank Meyer > > > PS we are hosting a Natural Building Colloquim later this month > www.naturalbuildingtexas.org and have a great caliche clay pit on > site. > > > -----Original Message----- > > From: Athena &amp; Bill Steen > > To: GSBN > > Sent: Sun, Oct 7 12:11 PM > > Subject: Re: GSBN:Re: Lime plaster problems > > > > > > 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&#xC3;&#xA1;s, Lleida, Espa&#xC3;&#xB1;a > >> rikkinitzkin@...> >> (0034)657 33 51 62 > >> www.casasdepaja.com (Red de Construcci&#xC3;&#xB3;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> > >>> ---- > >>> For instructions on joining, leaving, or otherwise using the GSBN >>> >> list, > >>> send email to GSBN@...HELP in the >>> SUBJECT >> line. > >>> > >>> ---- > >>> > >>> > >>> > >>> > >>> ---- > >>> For instructions on joining, leaving, or otherwise using the GSBN >>> >> list, > >>> send email to GSBN@...HELP in the >>> SUBJECT >> line. > >>> ---- > >> > >> ---- > >> For instructions on joining, leaving, or otherwise using the GSBN >> > list, send email to GSBN@...HELP in the >> > SUBJECT line. > >> ---- > >> > > > > Athena &amp; Bill Steen > > The Canelo Project > > HC1 Box 324 > > Canelo/Elgin, AZ 85611 > > absteen@...> > www.caneloproject.com > > > > ---- > > For instructions on joining, leaving, or otherwise using the GSBN > list, send email to GSBN@...HELP in the > SUBJECT line. ---- > > > ______________________________________________________________________ > __ > Email and AIM finally together. 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