Cob: Ceramic Cob

[Rosemary Lyndall Wemm]

Cobbers,

I've been reading Kahlili's epic "Ceramic Houses" and have come away with
some ideas others might like to try.

According to Kahlili, "mud-pile" walls [which are similar to Cob without the
straw] and rammed-earth walls can both be fired by the house-kiln method.
The problem is that such walls need to be fired from both sides as there is
no easy way for the fire-heat to filter through the wall in the early
stages.  This problem is over-come in the standard adobe wall construction
by leaving out the vertical mortor between the bricks which provides
vertical chinks for the fire wind to get through.

The straw in cob will eventually burn out leaving a kind of light
honeycombed brick.  This won't help unless the straw goes from inside to the
outside of the brick. Kahlili's suggestion is to poke sticks or small straw
bundles through the wall at numerous points.  This won't help in the early
stages of firing before the house-kiln is hot enough to burn through these
potential vents to the air pockets provided in the temporary mud-coated
straw layer on the outside of the structure.  Here is another solution which
might work, as well as providing artistic beauty.  If anyone tries it please
let me know the results.

1a. Collect some old glass coke bottles, or the like.  Try to collect as
many of the same types and size as you can; it makes things easier and the
result more artistically pleasing.

1b. (i)  EITHER collect some jam jars which are a little larger to use as
"lids"
   (ii) OR cut the tops of the bottles

        * Rest your bottle in a V grove placed hard against a "fence" of
something solid.
        * Use an ordinary hack saw to cut some groves about halfway through
the V at
          the length you want to cut the bottle.
        * Change the hack saw blade to one of the new glass-cutting threads.
        * Put the bottle in the V grove, push it up against the fence and
start sawing.
        * Revolve your bottle to cut the bottom off as well as the top.
          [Otherwise your marker groves would have to go all the way
through, wouldn't they?]

    (iii) Tape the two bottle halves [or the bottle and jar] together.
    (iv)  Paint the outside sides white or wind them with white tape or
cover them with a thin coat of white-wash.
     (v)   Put them aside for later.


2a. Collect 20 slightly larger [in diameter] high-pressure plastic drink
bottles [for fizzy or soda drinks].

2b. Make them into 10 place holders.

       * Cut off the tops of 10 bottles as high as possible
       * Cut off the tops of the remaining 10 bottles much shorter.
       * Almost fill longer bottle with dirt or sand.
       * Make a straw-sized hole in the top of the shorter bottle.
           - Put masking tape over the hole site [to stop the plastic
shattering]
           - Mark with brad awl.
           - Support the bottle piece
               [perhaps by screwing it into a bed of sand,
                but that will blunt the drill bit fast,
                so someone think of another idea, please ;-) ]
           - Drill a small hole, followed by a larger hole, followed by one
the right size.

       * Squash the sides of the shorter bottle and fit it on top like a
lid.
       * Put a straw in the hole in the lid and fill the rest of the double
bottle up with sand or dirt.
       * Tape the two halves together and put some tape over the straw hole.

3.  Design a wall with decorative holes in it at various points.  These will
act as "flues" for the hot air to move through during firing.

4. Use the dirt-filled place-holder bottles to mark the places in the cob.
Poke the "lid" as far of the outside of the wall as you can.

4.  Construct a dome or vault-style roof on top of the cob walls, using
small adobe bricks.

5.  Remove the dirt from the place-holder bottles.  This is easy if you can
take off the "top".  Otherwise you could take the tape off the end hole and
suck out the dirt [Yuck!].  Or cut off the ends and let the sand fall out.
[Other suggestions?]

5.  Cover the whole construction [or the part that is to be fired] with
straw with a mud slip "skin" and allow to dry for      a day or two.

6. Fire the thing and allow to cool. The plastic bottles will melt and give
off poisonous fumes, so don't stand close to the thing while this is
happening, O.K.?

7. When you have completed firing all the rooms, and the structure has
cooled down, fill the holes with mortored-in pipes, conduit and ... the
glass bottle barrels you prepared earlier.

8. Complete the process by painting the internal ends of the bottles with
the clear coloured paint used to make fake stained-glass windows.  Call the
sun out from behind the clouds then sit back and enjoy the effect.

 ==============

So, how's that for an idea?  Do I get any gold stars or elephant stamps?  Or
are there likely to be problems I haven't thought of?

- Rosemary



 ---------------------------------------------------------------------
 Rosemary LYNDALL WEMM,
 B.A.(Hons), M.A.(Neuropsych.), B.Mus.(Inst.), T.S.T.C.,etc.   _--_|\
 Clinical Neuro-psychologist                             Perth/      \
 Perth, Western Australia    lyndall at neurognostics.com.au  -->\_.--._/
 ------------------- http://www.neurognostics.com.au ---------------v-