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silica in wadding & wash

updated tue 15 feb 05


Sam Hoffman on sun 13 feb 05

My favorite wadding recipe is equal parts by volume coarse fireclay,
sand, silica, and sawdust. Just add a couple of scoops of each into a
5 gal bucket that is 1/4 full of warm water. The sawdust and sand keep
the wadding open, the fireclay makes it workable, and the silica keeps
it refractory. Open wadding mixtures are preferable to dense ones
because the atmosphere can penetrate the wads, leaving nice color on
the pots. Alumina sticks and also leaves nasty white marks that
contrast with the rich colors of wood firing.
I agree with Tony about Kyanite; it does wonders in sculpture bodies.
I really like the idea of using it dry on the top of kiln posts. Never
thought about using it in a wash, though. In the gas kiln, I use equal
parts EPK and Silica. Apply it thick and it just flakes right off
after firing. Not a good solution for vapor or wood kilns, though.

Just my 2 cents,


S.L. Hoffman Pottery
Corvallis, Oregon

On Feb 13, 2005, at 4:42 PM, clennell wrote:

> Sour Cherry Pottery
>> Hi Ivor, Tony, Lester,
>> I said I thought I might be missing something and was at least
>> correct on
>> that score!
>> `Making Marks` is a book at the top of my list. Had read my old
>> Nelson`s
>> `Ceramics, a Potter`s Handbook` ages ago. It`s plain as day there,
>> but I
>> must have just plain forgotten.
>> Thanks to you guys that `phobia` is gone, leaving only writing
>> glareing
>> mistakes to the list and precarious heights in the wind.
>> I will never forget the melting temp of silica again. :>)
>> Best wishes from least not scared of spiders or snakes
> Lela: Even if your memory was 100% something would come along and
> bite you.
> Mud pie, mud in your eye, mud on a snake bite don't you die- Guy clark
> I thought that alumina hydrate was the magic in a kiln wash. Took me
> five
> years to figure out it was the very thing that was causing me grief in
> my
> wadding material for the wood kiln. the wads would fuse to the pot. i
> thought it was ash build up but it was the damn Alumina hyddrate
> fluxing to
> the pot from the alkaline vapours caused by my wood kiln. i now use
> plain
> old cheap fireclay with sawdust in it for wadding. Pops off like magic.
> fireclay being a high alumina clay.
> I use another cheapie for the floor of the woodkiln and for placing
> large
> pots on in my gas kiln- kyanite. i also have a dish of water with a
> sponge
> in it and a plate of 30mesh kyanite.. I take the end of my kiln posts
> squish
> on the wet sponge and then place in the dish of kyanite. the posts
> don't
> stick to the shelf- a problem I was having because of the amount of
> vapour
> in the kiln.
> I just might try 50 kyanite, 25 silica and 25 kaolin for a wash in the
> gas
> kiln.
> Kyanite is an under rated material. i use it in my clay body instead of
> grog. It's cheap too!
> Cheers,
> Tony
> No snakes and spiders in Niagara in Feb- thank god!
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