The Kiln has been Loaded!

 

The kiln has been loaded with glaze tests that I hope to fire tomorrow. This 3.5 cubic foot kiln is an entirely manually controlled one, so I don't have a list of ramps, times and temperatures to share with you ahead of time, but I will simply switch it on early tomorrow morning and control things by adjusting the two knobs that control the upper and lower banks of elements as needed. I realise that I am rather out of step with the way things are done now, but nearly all of my crystalline glaze firings in the past have been done manually, and it is not that much of a chore!

In the "good old days" I would have fired the thing right through the night, but I really do need what little sleep I can get now, so I will be a bit easier on myself!

The results of many of the tests will be as much a surprise to me as they will to you, as most of the glazes are ones I have not tried before. Several of the glazes use silica, feldspar and at least one other flux to form the glass, but others are based on a high sodium frit. All the glazes have approximately 25 percent zinc oxide in them. The crystals that form should be zinc silicate ones, little glassy rods that tend to cluster and fan out in a circle around things that irritate them in the glaze. All going well, in some of the feldspar based glazes, we might also find a few tiny crystals of another type around some of the zinc silicate ones.... we will have to see!

If I can, I want to fire to just a shade above cone 8.5 to where cone nine is half over.  Armed with welding goggles, I will be judging that by peering at cones through a small spy hole, and I hope that I will be able to see them well enough when the time comes!

 Once the peak temperature has been achieved, then the kiln will be switched off and allowed to cool to about 1100 Celsius, then switched on again and I will hold that temperature for about 2 hours then switch off again and allow the kiln to cool right down. The two hour hold at 1100 C should allow any crystals that have succeeded in forming to grow to at least 10mm in size, which will be enough to show me which glazes are working, and which glazes are going to be difficult! When it come to firing actual crystalline vases rather than small test pieces, the time spent growing the crystals will be much longer, usually at least 4.5 hours.

I'm off to bed now.... See you in the morning!