[GSBN] Tall walls and wet clay

[Graeme North]

For making smallish quantities of clay slip I mix up clay in buckets  
using a paint stirrer attachment for an electric drill -
pretty quick and does a good job - I've done cubic meters this way  
now, and only on my second cheap drill

also good for making cellulose fibre out of shredded paper as a  
wonderful additive to clay to bind silts and to increase toughness  
and durbability

cheers

Graeme
Graeme North Architects
49 Matthew Road
RD1
Warkworth
tel/fax +64 (0)9 4259305

graeme at ecodesign.co.nz
www.ecodesign.co.nz


On 21/04/2009, at 2:25 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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