Civil Engineering Reference
In-Depth Information
From wet clay
From dry clay
First find your source of clay, test it as
described on page 109, and dig it up either
by hand or with a tractor. Dump it on a hard
level surface and start mixing it with water
and straw. The following are some sugges-
tions for how to do this.
You can usually get free milled clay from
a brickworks, if you collect it yourself. This
is dry clay, ground up into small pieces or
sometimes powder, that has been processed
ready to make bricks or clay pipes. Although
it's called clay it often has some sand in it as
well, so will always need testing. In this dry
form it can be mixed with sand and fibre in
a cement mixer, but another way to mix up
your plaster is in a large tub using a hand-
held plaster mixer (both dry and claggy clay
can be done this way). Three-quarters of a
tonne of milled clay will cover about 100m
2
when made into a 30mm (1¼”)-thick plaster
by adding sand and fibre.
•
Make a paddling pool by using a tarpaulin
draped inside a circle of bales. Place your
clay and sand (according to the mix you
already tested) inside this and trample
the whole lot by foot in wellies or bare
feet, adding water and straw as necessary
once the rest has mixed thoroughly. By
grabbing the sides of the tarpaulin you
can turn the mix over. This is a lot of fun
if done in a group, but takes a long time
and can be tiring.
From a manufacturer
•
Use a paddle mill. A local potter may
have one of these you can borrow. It's
a round pan with heavy wheels inside
that turn and squash the clay mix; as the
pan is turning the clay is scraped off the
bottom and sides and dumped back into
the mix to be squashed again.
Womersleys Ltd in Heckmondwike, West
Yorkshire (www.womersleys.co.uk) is at
the time of writing the only company in the
UK making clay plasters commercially. You
can buy ready-mixed base coat and finish
coat in tubs, and pure clay in lumps to mix
yourself for the first (key) coat. The base
and finish coats will probably need to be
tipped out into a bigger tub and mixed with
a hand-held mixer before you use it, as the
water in them tends to settle out.
•
Use a tractor to drive continuously
over the mix, scooping up the stuff and
turning it from time to time.
•
Use a clay-plaster-making machine. They
have really brilliant ones in Germany
and other European countries, and we've
found a great home-made one in the UK.
There are also clay plasters available
imported from Germany and Italy. They
come in dry form in sacks, and you just have
to add water. Different grades are available
for the base coat and finish coats.
•
Make your clay thoroughly wet first, like
a slurry, then you can mix it with sand
and fibre in a big tub using a hand-held
plaster mixer.
