[Cob] Easier mixing techniques to keep people loving cob

[Shannon Dealy]

On Wed, 4 Feb 2009, Ray Cirino wrote:

I probably qualify as one of the old timers of modern cob, and since I 
teach cob from time to time I've seen a fair number of people going 
through the initial stages of cobbing and have a mixed response to Ray's 
posting:

[snip]
> The thing that people don't like so much and keeps cob from growing 
> faster is the mixing techniques. When I learned how to do it, I was 
> turned off, because my hands,and feet were bleeding ever time I mixed. 
> It was from the sharp gravel and straw.

This problem will vary considerably depending on the local materials 
available, but surprisingly, my feet are generally softer than those of my 
students (I rarely walk around barefoot except when cobbing).  Over time 
reflexes have developed which keep me from putting my full weight down 
when my foot encounters a sharp object in the mix.  With harsher mixes, my 
hands do sometimes bleed, though I generally make heavier use of the 
cobber's thumb with these mixes, so the problem is often more the drying 
effects of the clay which a daily dose of hand cream deals with.

> My back, neck, arms, and body was hurting.

I had these problems when I started, I don't anymore and from what I have 
seen from students it is usually due to poor lifting technique and/or 
failure to adjust the batch size and size of "cobs" to what your body is 
capable of handling.  These days I am physically capable of handling 
batch sizes three times what I could when I started and I can do them all 
day long.  I got to this point slowly adjusting the size as my muscles 
and technique became better adapted to it.  My biggest problem now is that 
as my weight has dropped, I can no longer get traction on the ground when 
I am flipping a large stiff batch (never thought there would be a down 
side to losing excess body fat :-)

NOTE:  This is not some macho thing, larger batches take less time to mix 
relative to the total amount of cob delivered per day, and I have spent a 
great deal of time working out what the optimum batch size was for my body 
in order to mix and apply the maximum amount of cob in a day.

[snip]
> earth, not to work and be worn out. Here's a sample of how I see we all 
> could take it to the next level.
>
> http://people.tribe.net/raycirino/photos
[snip]

My response to the photos:

  - Free, tough plastic "mixing tarps", great!

  - Handles for easier grip.  Works for me.

  - Mixing by stepping on the outside of the tarp, fine for very wet mixes
    and high agregate mixes, bad for stiff/high straw mixes (I have used
    this approach for years under certain circumstances).  The tarp will
    work to spread your weight over to large an area to allow effective
    mixing of a stiff mix, you need to put the maximum amount of body
    weight in the smallest possible area, so walking on your heels without
    a tarp in the way during the final stages makes an enormous difference.
    Mixing while treading the outside of a tarp is also slower than getting
    your feet in the mix and keeps you from feeling the state of the mix.
    This is a common oversight by many people, having your feet in the mix
    allows you to easily detect problems with areas of the mix as well as
    better areas of the mix so that you focus your time and energy only on
    the parts of the mix that need more work which saves a considerable
    amount of time in creating a good mix.  If you find barefoot mixing
    with your particular soil/straws to be to much, you are better off
    switching to SCUBA diver booties, these will give you better feel and
    have far less impact on your ability to mix stiff batches.

> Comment included with one of Ray's photos:
>  "Without a strong billboard tarp and handles you are getting cut
>  knuckles,

I can't remember the last time I cut my knuckles, but it certainly wasn't 
from the mixing process, application on occasion does it, but the 
billboard tarp and handles won't help with that.

>  a sloppy area filled with clay that slows down production,

If the area gets sloppy, much of this is due to water/wet cob spilling off 
the edge which can be a problem with any approach, though water seepage 
through regular tarps is probably worse and may contribute more to the 
problem.

>  the tarp lasts a few mixes,

I'm not sure where you get your tarps, but half a dozen cheap two 
dollar tarps (on sale) are sufficient for me to do a complete building 
with my local soils/straw, and while coarser sharper soils and straw will 
shorten the life of the tarp considerably I've never seen even a really 
crappy tarp that didn't go at least 15-20 batches with sharp soils.  Not 
having put the billboard tarps to the test on some of the nastier soils I 
have worked with, I don't know how it will hold up, though I suspect it 
will do much better based on my limited experience using one at the 
Natural Building Colloquium last Fall.

>  slower mixing time,

I have to disagree with this one, barefoot mixing on a tarp (billboard 
or otherwise) is faster as noted above.

>  can't pulling cob to building area

Billboard tarp definitely does this better (it's slicker and less prone to 
tearing when sliding).

> or roll it into cart,

I have never had a problem doing this with a regular tarp, not sure why it 
would be an issue.  Except in a large group setting, it is usually best 
practice to mix right next to where the cob will be applied, so working on 
your own projects, neither of the above are issues (since you shouldn't 
need to be moving large amounts of cob around).

> and keep cob from progressing into where it should be.  People don't 
> like mixing and this solves that problem"

This one is a matter of perspective, I like mixing and when I have 
something I need to build, it is my morning "meditation"

As I said, this is something of a mixed response, I definitely agree with 
Ray on some points and disagree on others.

FWIW.

Shannon C. Dealy      |               DeaTech Research Inc.
dealy at deatech.com     |          - Custom Software Development -
Phone: (800) 467-5820 |          - Natural Building Instruction -
    or: (541) 929-4089 |                  www.deatech.com