[GSBN] Tall walls and wet clay

[ejgeorge at riseup.net]

Hi Laura,

Here were the responses from our NBNE list - Ben Graham seconds the  
vertical shaft mixer, Dave Lanfear gives several tips and suggestions,  
and Sarah Highland offers the German weathered clay technique.

ej

Ben Graham responded:
ej,
   We mostly use "wet" (non-bagged) clay in Vermont.  Our process is to put
it into 5 gallon buckets or large vats with water right off the bat.  Then
add to vertical shaft pan mixer to make it into clay slip.
   Drying it and pulverizing it also works in a hotter climate.  You end up
with powdered clay which may be easier for some to work with and create
consistent mixes.

Ben
-----------------------------------------------------------------------

Dave Lanfear responded:
ej,

I have experience processing dry lumps of clay from a site and wet  
lumps. processing dry is a miserable job requiring a soil shredder.  
The machine is loud and cumbersome, and its still a lot of work  
feeding it, though it does separate many of the stones. I don't  
recomend this from experience.
There are two processes I use for wet lumps. The first is the old  
fashioned grapemashing method of people using their feet. This isnt  
practical for most jobs, but it yeilds a beautiful thick slip, and the  
bonus of well toned legs.
  The method I have been using is soaking the clay chunks in barrels  
or bins of water and mixing it with a big mixing drill and a paddle.   
I've found this requires 2 or three rounds of soaking, then mixing.  
The result is a nice slip which, after pouring through a screen, can  
be used directly in the mix, obviously replacing some of the water.  
The rock and stones all settle to the bottom. I make  a few hundred  
gallons of this ahead of time for efficiency. A good mixing drill is  
critical. I have a dewalt, but a hole hawg works really well
I understand people using bagged clay for efficiency, but the key to  
that, I believe, is to use clays that you are familiar with and have  
tested, as two different brands of ball clay can have drastically  
different characteristics. I've used ball clays that can be mixed as  
high as 6 to 1 sand to clay, and have to be in order to avoid severe  
cracking.
I hope someone finds this helpful

Dave Lanfear
--------------------------------------------------------------------------------

Sarah Highland responded:
There is another method for processing clay, if one has the right  
set-up.   This
is to use the traditional German weathering approach, which is very easy.
In my case, my clay source is right up the road from my house, and I have an
arrangement with the owner of the pit whereby I send him $20 every time I take
a full pickup load out.  We go over there when it has been dry weather for a
bit and skim off the top inch of dirt over a wide surface area, put it  
in trash
cans, and store them in my barn for jobs.

Last fall two of us collected and stashed six cans in about an hour.    
The resulting
weathered clay mixes up very nicely, acting more like sponges than rocks.
It took maybe ten to fifteen minutes of paddle mixing per half-barrel tub to
make slip, and I think it would have taken much less time had we
soaked them overnight first.  Since then I have hired laborers to harvest the
clay a second time.   The key is to have fairly smooth ground.   The second
harvest was much harder than the first because the pit had been  
roughed up badly
with a backhoe in the meantime.

I have plaster recipes for pudding slip rather than dry clay, and it  
works fine
as I've gotten to know my clay.


The weathering method is the best I've tried, having rejected the  
Pig-pen method
(remember Charlie Brown's friend?) using a chipper, and having found making
slip from fresh-dug clay in a mortar mixer or with a drill to be slow  
and laborious.


Sarah Highland



Quoting cmagwood at kos.net:

> Laura,
>
> Breaking up wet clay is much easier if you have a vertical
> shaft mixer. We've been able to put very wet, sticky pure
> clays into this kind of mixer, add the sand and get a good
> mix. Same process would have killed any horizontal mixer
> I've ever met.
>
> There is a made in America brand called Imer that make
> great electric and gas versions of these mixers.
>
> Chris
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