[Cob] more on plasters & cob time

[GlobalCirclenet]

Thank  you for some hard, useful information, difficult to come by on this
subject sometimes.

paul at largocreekfarms.com
http://medicinehill.net
*********** REPLY SEPARATOR  ***********

On 8/1/2004 at 11:47 PM Buckaroo Bonzai wrote:

>Darel wrote:
>
>Yes, I know about the Japanese master mason, going to
>the U.S. for the session.
>
>> We just returned from a workshop at the Steens'
>> Canelo Project in AZ.  The 
>> Japanese master plasterer used 90% straw in some of
>> his finish plasters, and
>> as little as 10% (by volume) in others, depending on
>> the surface he wanted
>> to create.  Additionally, in Japan it's typical to
>> let the clay and straw  sit together for a year so
>the elements can "marry."
>
>This point is misleading however, unfortunetly.  
>Ideally, this would be the case and in the case of
>important buildings such as temples, shrines and rich
>peoples homes this is done for even two years.  For
>more common folk, in days of old, the mix would be
>prepared in the autumn and aged though to the next
>spring or summer when it would be applied.  It's also
>a little bit more complicated as more new rice straw
>is aged each month or   so and finally a few days
>before application.   Also note that this is mainly
>for the inner wall of a wattle and daub, not for the
>next outer layers.
>
>The current modern architectural standard in Japan
>requires a minimum of immersing the straw into the
>clay mud for two weeks prior to application.  The
>intend was to make using soil a faster process so to
>be a little more competitive.  The old methods
>required two much time  and time is now money so the
>old methods became uneconomical and unable to compete
>with fast cement fixes where no skill is needed.  That
>is why there are few of the master masons remaining
>and their knowledge disappearing.  Though many of us
>are trying to preserve as much of it as possible. 
>Just a historical note for you.
>
>
>This is different from the use of straw in a lime
>plaster.
>
>> The straw breaks down
>> so thoroughly that it almost disappears, but
>> apparently the fiber is still  there strengthening
>the plaster.
>
>More straw is added so you will have very decomposed
>small with then graduated sizes....
>
>> We saw "plaster"  corners that were 3"
>> thick, both on straw bales and on cob bricks. 
>Be sure to distinguish between the layers.  The finish
>layer is the thinnest and normally has a different mix
>or materials.
>
>> Finish plaster was done atop
>> those already thickened edges, sometimes another
>> inch or so thick.
>> 
>> My own experience echoes Shannon's.  The mixes I've
>> used for 1/2" plaster,
>> for 2" plaster, for 2-12" thick cob, and for floors
>> are all very similar.
>> 
>> Cob has always seemed painfully slow to me, but
>> friends here are speeding up
>> the process with tractor and tiller cob and also
>> using form boards so they
>> can do much bigger lifts at a time.  Mechanical
>> mixing means a drier mix,
>> which also can be stacked higher before spluging. 
>> Two people can put up a
>> cob wall of 20' in two days.  It's moving closer to
>> rammed earth but does
>> not contain concrete.
>> 
>> Barbara     
>> 
>
>Thanks for you input Barbara.  It was refreshing.
>
>Sent by Darel to us.
>
>Cheers
>
>
>		
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