[Cob] Re: composition of clay mortar for urbanite

[ocean]

The ratio of clay to sand for the mortar depends entirely on the purity 
of the clay being used.  There are many tests to use when mixing cob, 
especially the "crunchy" ball of cob which indicates that the sand 
particles are coated with clay, yet not too much clay.

Regarding the ground moisture affecting the mortar, my understanding is 
that the mortar doesn't necessarily need to dry or remain completely 
dry.  It is just a layer of compressed material to level the foundation 
stones/urbanite.  Ianto tells a story of medieval lime mortared 
foundations where upon deconstruction, workers found the lime to still 
be in putty form, after hundreds of years!

BTW, all this information is covered in vastly greater detail in The 
Hand Sculpted House, the primer on cob building by Ianto, Michael and 
Linda of the Cob Cottage Company.  I highly recommend getting a copy 
for anyone who wants to build with cob.  (Often the issues and 
questions raised on this list need in depth answers which all can be 
found in the book.)

And Carrie, if you're ever in our neck of the woods, come on by and 
check out what we cook in the oven, as amazing than the beautiful 
sculptural design.

Cob on,
Ocean Liff-Anderson
Proprietors, Intaba's Wood Fired Eatery
http://www.intabas.com

On Sep 2, 2006, at 3:34 AM, hms.mommy at juno.com wrote:

> Can you tell us some more about the composition and use of this clay 
> slip
> and sand?
>
> I don't understand how a clay mortar could work for a foundation;
> wouldn't ground moisture soften it?
>
> BTW Ocean,  I have seen the pictures of your huge oven, and they are
> amazing.
>
> Carrie
>
>
> On Fri, 1 Sep 2006 08:23:00 -0700 ocean <ocean at woodfiredeatery.com>
> writes:
>> Ianto uses clay mortar (very sandy mix of clay slip and sand) for all
>>
>> his foundations, and I don't see why this wouldn't work for an
>> urbanite
>> foundation, to level the "stones" of urbanite.  Traditional mortar
>> would work too, lime putty mixed with sand, but be sure to wear
>> gloves
>> when working with lime.
>>
>> Good luck!
>>