Saggar-fired shinos (continued)
The results of my latest saggar firing were very interesting! I fired two saggars in the same electric kiln, both of which contained combustibles in the form of a few small pieces of charcoal and a small piece of hard wood. One was sealed throughout the firing whilst the other was only sealed until top temperature had been reached (circa 1260 degrees c), after which oxygen was allowed to enter the saggar during the cooldown phase.
The results from the re-oxidised saggar were disappointing, with no evidence of reduction in the glazes whatsoever. I am wondering if the saggar was properly sealed and maybe oxygen was able to enter early in the firing.
The results from the sealed saggar were much more exciting as I achieved some dramatic iron reds and oranges with the different shinos tested. The three test pieces below have a shino glaze over a “rustic” stoneware body with yellow iron oxide brushed on. The one on the left has the iron oxide applied on top of the glaze, the other two beneath the glaze. 
The recipe for this glaze is:
Potash feldspar 55
Soda feldspar 25
AT ball clay 20
I was really pleased with the carbon trap shino below which was again applied to a “rustic” stoneware body. You can see the difference that the glaze application has made to the colour..the piece on the left was dipped for eight seconds, the one on the right for only three. 
The recipe for this glaze was adapted from one found on Ben Brierley’s website (http://www.ben-brierley-woodfired-ceramics.co.uk/):
Nepheline Syenite 52
AT ball clay 14
China clay 11
Soda ash 13
Red iron oxide 0.5
This last test piece was the “rustic” stoneware, glazed with a simple shino consisting of 85% nephelyne syenite and 15% AT ball clay. Before the glaze was applied, red iron oxide had been brushed on and then wiped off, to leave heavier deposits in the cracks and crevices. The glaze was applied milk thin and is therefore only white in a few areas where it’s pooled. Everywhere else it’s formed matt and satin rust-reds.
Several factors may have contributed towards the improved glaze colours in this firing. The smaller amount of charcoal used may have resulted in a lighter reduction. Also, the inside of the saggar was coated with a wash of red iron oxide. The cooling phase too was much slower, which may have allowed for better colour development.
