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low fire info - clay

updated thu 16 apr 98


Hermsen on wed 15 apr 98

It seems that there is an ever increasing interest in low fire work and
therefore it is not unreasonable to expect an increase in technical =
questions as
well. A number of these keep cropping up on Clayart. I have been working =
fire for some time and by way of maybe addressing some of these questions, =
like to share what I have found to work.
I have arranged the topic into obvious catagories, Clay, Glazes, Decoration =
Firing. Since this makes for a rather lenghty posting, I will post it in
installments over the next few days - time permiting.


Redart Clay Body cone 04

Redart clay 65 pounds
Fireclay 20
OM4 ball clay 10

Water 26
Barium carbonate 2 teaspoons
Bentonite 4 teaspoons


Wear appropriate dust mask. All of the ingredients have their own bucket =
with a
line marked on the bucket indicating the amount to use for a single batch. =
the required amount of water in the mixer - add the barium carbonate and
bentonite. Start the mixer. Add the ball clay and then the redart clay. Add =
fireclay. If the clay mix in the mixer seems too soft then add one scoop at =
time of a previously made =22dry mix=22 to stiffen the batch to the right
consistency. The =22dry mix=22 is the above formula without the water of =
course. Mix
for 20 - 30 minutes then run the batch through the pugmill. It is a good =
idea to
let this clay age for a few weeks before one begins to work with it. All
earthenware clays improve remarkably in working characteristics when allowed=
age a bit.


To recycle scrap clay, do the following:

In a large container, make up a =22dry mix=22 of the regular Redart Clay =
Body. Make
sure it is very well mixed. Fill scrap buckets about 1/3 with water. Shovel =
dry broken up scrap clay until clay sits above water. As the clay slakes =
into the water, add more scrap clay. Leave to soak over night. Dump a bucket=
scrap into the mixer and start mixer. Add dry mix by the scoop untill clay =
the mixer is of the proper consistency. Mix for 30 minutes then run the =
through the pugmill.


When joining coils or slab building, it is necessary to use =22potter's =
glue=22 to
insure that the clay joint is strong. Joining slip can be made from the =
throwing slurry provided the slurry is not too lumpy and has been allowed to
settle so that the excess water can be decanted. The slip should be of a =
creamy consistency and should be brushed on sparingly when making a joint.
Joining slip can also be made from the following recipe:

Redart clay 570 grams
fireclay 180
OM4 ball clay 90

add water to make a thick cream.

O.K. so now you have a clay body aging, you know how to recycle your scrap =
and you have slip to stick things together with. Go make some pots and in =
next post I will run through the glaze formulas, etc.

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