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With the confidence given by one year experience in casting, that is 4 successful pieces, I suggest: Cast the mold in a saggar if possible. That is make a box of clay and fire it. Then cast the mold into the box. The ceramic outer surface can take the tensile stress caused by 8 ponds of glass. If th...

Thanks for all the tips, I'll try plaster-silica as soon as I can get silica sand. For the innermost layer I use one part plaster, 2 parts Aluminnium oxide. That gives a satine surface to the glass. If possible to reach, I gently rub the surface with a soft cloth and the vacuum the dust off. The coa...

Frit casting open face reliefs, I use ceramic molds with kiln wash. That works OK. When casting deeper, solid objects I have used a mold mix of plaster, kaolin, grogg or luto. The wall thickness is about 1 ½". Cracking is a problem. The molds seem to survive the ramp up. Somewhere above 700 C ...

Sorry to see how the table came out.
The columns are
Temperature in Centigrades From, To,Description, Temps in F From, to.

Hope this helps reading.
-lauri

The first anniversary of my kiln is approaching. Looking back, I tried to summarize what I have learned. Below is a table collected from the board. Is there anything important missing? Is there anything you disagree with? Critical points Critical points C Event F from to from to 40 240 Plaster calci...

Just learned it by the hard way! The area does count ! ! Take a one inch button and a ten inch plate. What ever is the residue of stress after annealing, in the 10" plate it has a tenfold moment to break the glass. So you must be more careful in annealing. This applies to the warm up stage, too...

> ON THIS SITUATION OF CALCINATED, NO >LONGER RELEASING CHEMICALLY BONDED WATER,,,, > is the release of this water, what makes the >mold stick to the glass I do not think so. My suspect is the ceramic compounds in the mold mixture. They start to sinter or fuse at the higher temperatures. Was it Hugo...

As I understand, the *area* is relevant only to a side element kiln. The heath escapes the shortest way. A flat sheet loses heat over the top surface, and maybe thru the shelf. I do believe that even the shelf is cooled mainly thry the glass. *Under* a large sheet near the bottom of the kiln, there ...

Thanks again for encouragibg ideas. There are some practical limits, like money and space. My studio has no room for a car kiln. My studio is at a rented space, where I am limited to a total of 12 kW of power. The ring kiln construction has a point. If it is a fiber kiln, then lifting the rings with...

Yes I know, that I'll need two conttrollers for the dual chamber kiln. What I have in mind is That the upper chamber serves as a small testing kiln, too. And I can first rig it on top of my current kiln. In stead of down payment, I buy it stepwise. My final goal is to be able to cast 2-3 feet tall s...

The manufacturer is

Varnia Oy
Kisko
FINLAND

if it helps you Rosanna
may be a little far away.

-lauri

hanks, Bert, Fortunately I do not have to build my next kiln. A local manufacturer makes custom design kilns at a reasonable price. The chemically bonded water (released around 700 C =1300F, is that right?) was the reason I wanted to heat up the mold before melting the glass. My slumping kiln has a ...

When I begun with glass, I expected to do mainly slumping. Therefore I wanted a fairly large bell kiln: 50x70 cm with 40 cm height. That is enough for many castings, but with flowerpot method the height is restrictive. I'm deaming of a two chamber kiln. A side door kiln, with more height than width....

When making molds for pot casting (880 C) I make the innermost spalsh layer of plaster and aluminium oxide in 1:2 ratio. It leaves a smooth surface - like sandblasted . Caolin tends to sintrate in higher temps making porcellain that sticks. Plaster calcinates at 740 C and loses the strenth. It is ea...

In my bell kiln I have two circuits behind one controller. The side and top elements have separate relays. If one fails ON, then the controller will shut the other when the temp rises. Either element can reach no more than 700 C alone. I would like to add a gold wire fuse, too. At the moment I can't...

When making ceramic molds, remember to work carefully with the clay, so that no air pocket are left. Raku clay is good, it is made to tolerate rapid temperature shifts. Other good materials are clay with chamotte (=grogg). that improves resistance to thermal shock. Paperclay (clay with cellulose fib...

Jerry, as you have realized, you can use a nonsolid plug only if the glass is kept in place otherwise, that is pate de verre. Then two questions are left: Does the glue have enough time and room to vaporise away? When the glass is fused, it is packed more closely. Is there a risk of plaster particle...

Thanks to everyone.
I'll wash the glass more carefully, melt the flat pieces
to a higher temp and load the relief molds unevenly, so that
the glass moves more while melting.
I'll experiment with flux, too.

In Lundstrom book there was tests how much better
a mixed size frit packs. The frit size has to do with
the opaqueness of the glass, too.

The larger frit, the more transparent is the result.

-lauri

I have used reject "pilt" glass fron a local glass factory. It is broken pieces of clear glass vases, about 1 cm thick. When I fill a flat open face relief mold with a layer of this frit, the fired piece has thin opal lines thru as if there were spider webb in the glass. When casting in a ...