Lawrence Carter on sun 15 nov 98
Hello Craig Martell,
Thank you for your interest in my questions and your reply.
The idea of using 'draw trails' is promising. Perhaps a little
dangerous to use a steel rod to probe into an electrically fired kiln.
The actual spy holes in my kiln are about 35mm in diameter which renders
access difficult yet I still find the idea has merit . Forming a large
spy hole in my electric kiln ,the outside being lined with thin
stainless steel jacket is a little daunting .
I was wondering if it was possible to predict the melt point to within
+- 20 degs C by a calculation method, if so how ?
In message <001f01be0f92$e26eb2e0$1a896ac6@pavilion>, Craig Martell
>I remember one of your initial questions about finding the fusion temp of
>your crystalline glaze. One way to approach this is to use draw trials.
>Make some coils and form them into small circles that will sit upright and
>place them in the kiln near a spy so that you can pull them out at different
>temperatures. Just glaze the upper part of the coil because of the runny
>glaze factor. Watch the pyrometer and pull trials at temps where the glaze
>is likely to start fusing. I use draw trials in the salt kiln, and pull
>them out with a thin steel rod. Wear gloves!
>As for the slip-engobe thing, am I correct that you are placing a slip over
>a glaze? If so, the curling that you are getting is normal. Slips will
>almost always have a higher clay content than a glaze and will shrink more.
>This will cause the curling and crawling. You will need to calcine some or
>most of the clay in the slip to get this to work. Multiple application
>methods are tricky and crawling and shelling is a common problem. Try to
>apply one material over another as soon as the initially applied glaze or
>slip loses its sheen but hasn't dried and done all it's shrinking. Timing
>can be a critical factor. Applying raw slip to bisque ware is not usually
>successful unless you've calcined some of the clay in the slip or reduced
>the raw clays considerably. This is a tough one to answer well and I hope
>I've helped a bit.
>regards, Craig Martell in Oregon