Monday, 26 December 2011

Firing parameters and clay Cone 6-7 tests Electric kiln

Happy New year all,
Have spent the last couple of months preparing and formulating Cone six glazes using materials available in New Zealand. I am very interested to discover some clear glossy food safe, base glazes to experiment with hopefully they will also give me some base lines to develop my own unique glazes which I will post on here,most of the glazes were from Hesselberth and Roy,Mastering Cone Six Glazes and also from Micheal Bailey’s,Cone Six glazes.One was from Janet De Boos and one I developed from scratch after analyzing the alumina and silica levels.
I was using Lawrence Ewings computer glaze program called Matrix to reformulate and replace materials,which I am comfortable with.I find it an easy program to use.
Clay bodies used:
MFW(midfire white,smooth white firing throwing clay for Domestic ware,200 mesh Fires C 2-6,shrinkage about 15%
LF18.course off white body good for throwing and hand building,,50 mesh, shrinkage about 17% Fires C7-8
N21, iron rich stoneware, 50 mesh, shrinkage 16% Fires C7-8

My Firing schedule to 1201 *C Cone 6,was also slow cooled at a ramp of 80 oC to 800oC..I do believe it is important to slow cool and have seen a huge improvement from doing so.
Bisque was to cone 08 (955),Soak one hour.I may increase the bisque to 1000 to reduce further any problems.
NB. R=Ramp per hour T= Temp in Centigrade, H=Hold in minutes
R1 60
T1 100
R2 100
T2 600
R3 150
T3 1150
R4 80
H 20 mins
R5 80
T 800
OFF natural cool.
Actual temperature was Cone 7 tipped

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