[GSBN] Tall walls and wet clay

Tue Apr 21 03:19:35 UTC 2009

ej,

This is a great collection of thoughts from good folks. Thanks so much  
for putting it out to the NBNE list.

I tried working with different batches of the clay both wet and dry,  
and found that it dried fairly easily, and was not too difficult to  
break up and sift. However, having now done some research into the  
vertical shaft mixers (thanks Chris), this seems like a very good  
option with the wet clay.

Has anyone experienced working with the vertical shaft mixers with  
clay that has some (not a lot) 2" minus aggregate in it? It seems to  
range from 1/2" to 2" mostly, and am wondering how the vertical shaft  
mixers would handle if you were to start from the wet clay. Would you  
be forced to soak first anyway in that case?

It's for a fairly large project, so there's a lot of motivation to get  
the processing system right :).

Laura

On Apr 20, 2009, at 8:25 AM, ejgeorge at riseup.net wrote:

> 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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>>
>
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