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clay for cob wet? or dry?  RSS feed

 
heidi shackelford
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OK so i found an abundance of clay on sight, it is mixed with some sandy loam and rock. my idea is when it's time to make my cob, can i mix my clay soil with water till it's pourable, then pour through screen to remove rocks and use immediately? or do i really need to go through the whole process of letting the sand settle out, drying, crushing, and add all the water when i mix the cob? if this is possible it will save me tons of time and labor. i have a drill and paddle so mixing it nice and smooth will be easy and help it go through the screen. i have read that letting the cob sit over night makes for a stickier cob and gives it more elasticity just thought if i don't completely dry the clay then it will always have the sticky and elasticity it needs? your thoughts and comments please and thank you.
 
Jay C. White Cloud
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Hello Heidi,

I may not be grasping what you have described as a process (I will defer to the other cobb experts on that) but your described process will probably create much more work. You are going to lose a lot of your clay particulate with the water. This is one of the ways major clay producer clean and filter clay, but they have large pumps, settling ponds/chambers, etc.

In general, Cobb-Bousillage-Adobe architecture is a lot of work, there really isn't a way around that without use of heavy equipment and/or mega manpower. Its really fun, but there is no really way around it, ITS WORK!!!

If you have good clay layers, you should be able to get down to a band of "purer" clay that will need less processing.

Good Luck,
 
allen lumley
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heidi shackleford : Assuming that you have made up a series of sample Cob bricks and have subjected them to drop tests to test for durability, then you have working
Cob/Sand and Cob/Sand/Straw Ratios dancing in your head ! With that as a given, yes I think you can proceed as you have planned ! I have read of renting a concrete
mixer once a week and making up three or four days ahead !

Two thoughts, you will need lots of help, use these forums to announce your location and potential build dates, and dragoon all your friends! You can never have to much
help! And you my find that you have a near neighbor with Cob Experience !

I Can only state that I am in awe of the amount of information in Evans' et al (s) Book The Hand-Sculpted House available from cobcottage.com, through your local
lending library, Amazon or my Favorite used book seller ALIBRIS , Also highly recommended - though I have never seen it is - Mike Smith's The Cobber's Companion
G"luck Big AL - Think like fire, flow like gas !

Late note : What ever Jay C. White Cloud says ! A.L.
 
Jay C. White Cloud
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Late note : Whatever Jay C. White Cloud says ! A.L.


Thanks Allen...that made me laugh too hard...I had to go find a tree!!!

Hi Heidi,

The books that Allen suggested are the go to resource for most of us as well, unless we are getting into some historical restoration and/or esoteric vintage Cobb-Bousillage-Adobe architecture of some kind. I have been trying to put together reading list for folks on Amazon that they can just go and look at for the different skill sets. Once complete I will try to post it here on Permies.

I must admit that 99% of my "mud" work is either small scale educational (mix a batch by hand and build say an oven or a few bricks) or it big and heavy industrial type (paid architecture with heavy equipment, mixers, etc.) The "mud party" stuff is usually going on while I get a timber frame ready, so I would defer to Allen's guidance when every you have a question about "mud" stuff, he has probably done way more than I in regards to contemporary cobb.

I remember you mentioning having a possible lower back challenge, and I know what that is like! This kind of work can really strain that region. I was wondering if you have looked in "clay straw" work? It may very well be applicable for your application. This is a "slip form" process, but should work very well with "clay straw" and your cordwood wall.

As I had said in our first contact, much of my work is in historical context, so that is how I look at many of these modalities, even cordwood-"stackwall". Original "stackwood" nogging, as Roy and I have discussed it, was typically not left exposed, especially on the outside of a structure that would be a house, (barn yes, domestic architecture no.) So for a house, the exterior would get a final parging of cobb, then probably a lime render finish. The interior could be finished off in numerous ways depending to culture of the region. I know that my next "stack would" will most likely be a "slip form" type like you would find in the Middle East or China.

Best of luck to you,
 
heidi shackelford
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thanks guys, and yes i am ordering the books. i just wondered about that this morning so i thought i would ask.

heidi shackleford : Assuming that you have made up a series of sample Cob bricks

no i haven't been able to, as i am still waiting for the clay i have dug up and processed to dry out.

that's what got me thinking.... is that necessary? just seemed to me, i really just need the rocks and roots cleaned out and that was the best way i came up with and least amount of lifting etc., i have lots of 3 gal buckets the i can lift easily as long as they are not full. 4 wheeler and wagon to keep them up higher and move them around. really was looking for the most efficient way to clean the clay for using in cob. all the info i have found is cleaning it for pottery. that's what i have been tinkering with so far.

and thanks Jay for the clay-straw idea i will do more research on that as well.

 
allen lumley
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Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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heidi shackleford : I have no problem with you waiting to get your hands on the two books I mentioned,before you proceed with making Test bricks of Cob
but Yes, every batch of clay is slightly different ! You need to know how much sand ,and / or sand and straw you will need to have a finished product that will
stand 'the test of Time' None of these tests will prevent Slumping or Spluging but will help your structures resist cracking !

Jay C. White Cloud gives me too much credit my total cob experience outside of rocket mass heaters does not add up to one days hard work, If you continue
down your present path, you soon will be the experienced Permies member others will be turning to for knowledge and help ! Good Luck !

For the Future Good of the Crafts ! Be, safe, keep warm ! As always your comments and questions are solicited and are welcome PYRO - LOGICAL Big AL !

s
 
aaron bellomo
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Heidi how much organic matter and rocks of what size are in your soil? It may be fine, you'll just have to wear shoes or use a bobcat to mix.

As for the sticky mix i think the clay soaking into the straw longer is mostly what accounts for that. But the test bricks will tell you the most.
 
heidi shackelford
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Aaron, i have quite a bit of stone from pea size all the way up to 1" to 2". as well as the grass and weeds growing on top. i tried to sift out the stone but the damp clay just clogs the screen. it seems that if i mix it with water till its pourable then it will pour through better and i will have a good mix of clay and some sand. i can always add more water if needed. i have seen it made both with dry clay and wet wondered which was better. I wil know more after i have a chance to do some test blocks next week. thanks for your help.
 
Tys Sniffen
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Location: Northern California
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we did different things to clean our clay. we had dug most of it during the foundation making, so it sat out for a year or two and got a lot of crud falling on it from the trees and such.

at first, we would shovel dry clods onto our tarps and crush it with our feet, then pick out or sift the junk out of that powder. as the summer got drier, that wasn't really possible, so we started filling half a 5 gallon bucket, then adding water to cover and letting it sit overnight, after stirring vigorously after about 1 hour. Then we just used our hands to reach in and pull out leaves, roots, and rock bits.

then we had basically a bucket of 'slick', somewhere between oil-based paint and pancake batter, which we figured out the ratio to add to our sand and poured on each batch.

here's a photo of my wife working on cleaning clay from our blog:
http://journeyinthewoods.blogspot.com/2009/11/work-contiues-on-melissa-works-everyday.html

 
leila hamaya
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both wet and dry.

thats my vote. have huge amounts ready and prepared that are both wet and dry and add them together when you make a batch. having some leftover dry clay is good, you can add it in as you go as needed.

sort of like making bread how you add some flour while you mix it together...you kinda add a bit of powder as you are completing a section, or to adjust it as it seems needed.

i think you can use most of it straight, but settle and seperate some of it. put screen over buckets and add a lot of water, wash it into the buckets through the screens. then pour the water off and then as it dries it settles in layers
 
heidi shackelford
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thanks everyone for the great info. very helpful !!! can't wait to start that part of my build, i hope to get some friends over to play as well.
 
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