Fail Number 2

Fail number 2, time to build different vessel with new clay. My kiln at cone 5 fires to cone 4 temp so logic says cone 6 should fire to cone 5 temp eh? Nope six on the dot. No worries though. I’ll make something even better ūüôā

This clay, which I believe contains manganese, needs to not be over fired and needs a loooong bisque to burn off any gasses and other things that can cause bloating. Which I did. A 13 hour slow bisque to cone 05. But in the end it blistered anyways because of over firing.


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)

Jet-Dry and some old black clay with manganese as colorant
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.
Poke a hole in that mug! Just above the heavier solids.
Drain into some kind of container
I’m impatient so I boiled off the excess liquid by about 1/2
1/2 cup morning piss (aka terra sigillata!)
You can see a bone dry burnished piece with a few coats

Chemicals contained in Jet-Dry

Tetrasodium EDTA
Citric acid
FD&C Blue #1    
Sodium Polyacrylate    
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.