Interactions between Two Glazes
cone 10 oxidation
Firing profile
Up Fire profile
150 deg F an hour to 250 deg F
400 deg F an hour to 2050 deg F
120 deg F an hour to 2310 deg F with a hold of 20 minutes at 2310 deg F
Down Fire Profile
A half hour hold at 1750 deg F
A three hour hold at 1700 deg F
slow downfire at 25 deg F an hour in the interval 1700 deg F to 1650 deg F
A one hour hold at 1650 deg F
The cones show this as a cone 10 firing.
This glaze is in the family of silvery oil spot glazes, yet has no oil
spots. The upwelling channels which produce
the oil spots in other of the
glazes in this family have diffused at the surface to leave behind
indistinct
disks of a distinct texture from the background.
On entering the kiln, the contrast inlay glaze abuted the background
glaze. There was no overlap or gaps between the two.
Nevertheless In the
closeups, one sees disks of the contrast glaze as islands within the ground
glaze,
separated and cast free of the remainder of the inlay by the force
of the upwelling glaze material within the spouts.
Those isolated bits of
the inlay glaze show the turbulance within the glaze. Under different
circumstances
those spouts might have produced oil spots.
Other glazes in this family
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
I show details of the interaction at the interface between the glaze inlay and the background glaze on a bowl ~6 inches in diameter.
I also show a picture of the bowl.
glaze composition of the two glazes
Emperical Formula mashiko_Z13_1 - background glaze:
K2O 0.15
Na2O 0.13
Li2O 0.12
CaO 0.30
MgO 0.30
Al2O3 .81
Fe2O3 .28
SiO2 5.61
molecular percent Silica 73 %
Emperical Formula candaceBlackB - inlay glaze:
K2O 0.32
Na2O 0.15
Li2O 0.00
CaO 0.39
MgO 0.14
Al2O3 .62
Fe2O3 .24
SiO2 5.36
molecular percent Silica 74 %
The markings on the outside of the deep bowl are a second glaze inlay. The
glaze is filled in to an area that had been masked prior to
the pouring
of first layer of glaze. It was then waxed with an emulsion wax prior to
stripping the mask.
This is the method whereby the raw background glaze and raw inlay glaze abut with no overlap.
Close up Images of various of the markings
Image of the whole piece
inside of bowl with glaze mashiko_Z13_1
outside of bowl with glaze mashiko_Z13_1 and inlay CandaceBlackB
The spots in this glaze, the relics left at the surface by the upspouts in the
glaze have their own texture, distinct from those
of the other glazes in this
family. The effect of the formation of those spots is seen in their interaction
with the inlay glaze.
The closeup images were edited to give greater contrast, which distorted the colors.