Processing my dug clay

Initial processing of my dug clay from Fforest Fawr near Tongwynlais, and shaping it for experiments and analysis.


After drying up my clay at home and braking it into smaller pieces, I brought the dried clay to the studio where I covered it with water to soak and brake the dried pieces up again.

Leaving it for a few days to sit and braking it up a bit more with hands I noticed how my substance is more like a sandy mud, than a clay.
I decided to screen it first through 30 mesh sieve to remove any larger sand, rocks and organic debris more easily, and then again through finer 40 mesh sieve.

20151030_141257
My very short clay, most likely very high in organic compounds.

The process was very strenuous and incredibly smelly, the clay substance releasing powerful sewage odours, giving me more proof that what I have is a highly organic and sulphury substance with little clay in it.

When I removed all larger sand and organic debris with the sieves, I poured the wet mud onto a plaster bat to soak up excess water, and tried to wedge it into a one ball.
The substance felt rather sandy and as sand is a non-plastic part of a clay, I knew that my clay would be very short and lack plasticity.
This would make it difficult to shape my clay into tiles for further testing, therefore I decided to integrate some clay available in university to make it more plastic and malleable and see how the two clays would react.

There could be another option on how to separate and retreat the clay from my dug substance, using levigation. However, that was the more time consuming process and I already felt slightly behind with the task.

I decided to introduce the same amount of porcelain as my dug clay; choosing porcelain for it’s plasticity and whiteness; so that any colouring from my raw clay would be more noticeable.
Wedging the two clays together, the mixture was still too short for my likings, so I added a bit more porcelain.


Totally my clay mixture consists of 1296 grams of my raw dug clay and the same amount 1296 grams of porcelain with extra 300 grams, as the mixture was still too short. That is 44.81% of clay sourced in Fforest Fawr and 55.19% university’s porcelain.

Raw clay test tiles
The test tiles and 100 grams balls.

 

I ended up with a more plastic and malleable clay, but also more porcelain than my dug clay.

I managed to shape the original raw clay at least into a ball of 100 grams, to test the water content in the dug substance.
The clay mixture was also shaped into a 100grams ball to see the weight difference compared to the pure raw clay, bone dry and then bisque fired; suggesting the amount of water as well as chemically bonded water in the clays.

The test tiles from my porcelain and raw clay mix will be fired to different temperatures raging from just bone dry, biscuit fired to 1280°C reduction.
This will demonstrate changes across the different temperatures as well as the shrinkage rate, when measuring the 10cm long line marked on the tiles.

After drying for few weeks and then weighting the 100 grams balls again, the difference in water content was 33.3 grams for raw clay and 26.1 grams for clay mixture with porcelain.

 

 

 

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Published by

Marek Liska

https://ceramicliska.wordpress.com/

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