Terra Sigillata

Long story short, I needed a small amount of Terra Sigillata by way of alternative chemicals. Well after literally hours of research and no answers from any of the clay forums I created my own recipe for Terra Sigillata. I needed an alternative to sodium silicate as none is on hand and I’m impatient so I’d rather play kitchen chemist and see what I could come up with. It’s not rocket science. So I thought I’d share and save some folks from having to go out and find sodium silicate.

1 Parts Clay – I used a manganese wet clay (everything else calls for dry ball clay and I was not sure about using wet clay but it worked out fine)

3 Part Water

2 Teaspoons Jet Dry (for deflocculant)

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Jet-Dry and some old black clay with manganese as colorant
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Shake it up and you can see the separation clearly after an overnight sitting. The entire top was filled and I only got a picture after I had drained most of it. There was no layer of clear water on top. Entirely Terra Sigillata.
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Poke a hole in that mug! Just above the heavier solids.
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Drain into some kind of container
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I’m impatient so I boiled off the excess liquid by about 1/2
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1/2 cup morning piss (aka terra sigillata!)
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You can see a bone dry burnished piece with a few coats

Chemicals contained in Jet-Dry

Tetrasodium EDTA
Citric acid
Methylisothiazolinone    
FD&C Blue #1    
Water
Sodium Polyacrylate    
Methylchloroisothiazolinone    
Sodium cumenesulphonate

I think the Tetrasodium EDTA is the main source of deflocculant as it is used for a chelating agent and sequester and decrease the reactivity of metal ions that may be present in a product. DigitalFire lists Tetrasodium Pyrophosphate in their database of deflocculants, which is not the same as Tetrasodium EDTA but it seems to do the same thing.

The knife is a Kiridashi made from a recycled tool file by Jared Kramer Studios. The handiest knife I’ve ever known.

Understanding Core Materials

Years and years ago I got up the courage to develop my own black and white film after reading an article that gave me the very basics in a way that I could understand. That understanding only took place after researching over the period of many months.

I’m experiencing the same thing with glazing. After seeing the results of cone 10 glazing and seeing the depth that it creates I’m ready to take it on.

Cone 6 in oxidation just pales in comparison. It looks as if there is a film of glass on top of some clay. Sure some of it looks good but cone 10 just has something that makes it sing. It’s as if the glaze is a part of the clay itself.

This article from Ceramic Arts Daily, along with John Britt’s excellent books on mid range and high fire glazes just pushed the right buttons for me and I’m ready to go.

rawmat_main_500

I had previously bought chemicals for some cone 6 testing so I have a lot of 2 gallon buckets with a lot of the chemicals I need but cone 10 calls for some specifics. So I’m off to my supplier in a few days to pick up the rest of what I need.

I’ve made up some small pinch pots to test without fear of melting stuff to the kiln shelf. These will also be to test the creation of a black englobe to go along with the buff white clay body I’m using. I want to get 2 complimentary glazes, and with the color of the at body and a black englobe I will have a decent start for decorating and making functional wares with my OWN glazes.

I’m very excited to get some good reliable glazes:

  • Temmoku
  • Celedon
  • Oribe
  • Cream White
  • Nuka

🔥🔥 I’m fired up! 🔥🔥

Future Experiments

I found my first cone 6 recipe that I want to try – Falls Creek Shino!

ranlett2

My supplier Stone Mountain Clay sells dry chemicals I recently found out so I’m ready to go!

http://ceramicartsdaily.org/ceramic-glaze-recipes/mid-range-glaze-recipes/recoloring-a-classic-trying-new-colorants-in-a-classic-pottery-glaze-recipe-can-lead-to-some-great-results/

http://plainsmanclays.com/albertaslip/index.php

http://www.redhillpottery.com/cone6tests.html