Egyptian Paste, Wood Ash and Skipping a Zero

Well, I'd been planning to do a firing to test some things out again since April, but it's taken until this weekend to be able to do it. And it was a great firing, with just enough going almost right as well as totally wrong...

I fired up a bunch of pieces, including another try at Terra Sigillata, and new experiments with Egyptian paste (using the homemade copper carbonate), and Wood Ash glaze.

I sifted the wood ashes through a simple kitchen splatter screen (not sure what mesh it is, although the chunky bits sure got left behind), and didn't bother washing them as some suggest. I then mixed up three different batches...

Recipe 1
Wood Ash       38
Feldspar          36
Clay               18
Silica               8

Recipe 2
Wood Ash      50
Feldspar         50

Recipe 3 was Recipe 1 with 2.5% of copper carbonate added, just to see what would happen.

...and applied them to three little glaze testers, as well as to a bisqued plate (Recipe 1), a pot plate (Recipe 2), and a coil pot (Recipe 3). Yes, I did these glaze tests mainly on ware that hadn't yet been bisqued, which was probably not the best way to go, but there you go.

you can see how thick the glaze went on when applied

The Egyptian Paste was as follows:
feldspar (pumice)  40

silica gel powder    20

clay                      20

baking soda          12

CuCO3                 3

it mixes up very thick

The paste is very difficult to model because it's so granular, so I ended up making a flat little human figure shape which I never took a photo of. It would work well in a mold (next time).

All of this I cooked up in the kiln for about 7.5 hours.

11:30       150° C/hr ramp for 2 hours  (basically I kept this ramp throughout)

1:30         350°

3:30         600°

4:20         800°   

5:10         955° (soaked here, Cone 08, for 1 hour)

6:10         began dropping temp. about 350°/hour

7:00         turned off flame, covered up chimney and let it sit while I went to walk the doggie

And this is what came out:

This time the terra sig worked. The thumbpot with terra sig has a very nice finish on it, perhaps finer than the burnished thumbpot I used for comparison. The wood ash glaze was a total failure, perhaps because I didn't sift it finely enough and laid it on too thick, ending up with a burnt powdery substance all over the pieces. The coil pot had little black specks, which are actually slightly blue, so I figure that's the CuCO3 that was in the glaze.

But the main reason the Ash Glaze didn't work is because I confused Cone 8 with Cone 08! I had a note saying fire the glaze to cone 8-10, and another note saying the paste and terra sig would be good at Cone 06-08, so I figured Cone 08 would be a good average, not remembering that there's a big difference between "08" and "8" - I was off by about 300°!

But now for my favourite, the Egyptian paste man (which I had fired standing up inside the coil pot) ended up folded over onto himself because he couldn't stand the heat... The nice thing is that the blue colour emerged, so the paste (and the homemade CuCO3) works. I was reminded of the Popul Vuh and other creation myths, where the gods at first try to make a little human out of X or Y material, and it doesn't work, and they have to try again until they get it right...