Art Help Please?

Question

I have a few questions on pottery...

Kilns are often heated through “peep”holes. True or False

I think that's true...

How much can a pot shrink by the time it is “Leather Hard”?

At what “degrees F” temperature does a small 05 cone bend at ?

Answer 1

Peep hole are just looking through many people set there pyrometric cones so they can see them through the peep hole and gage the digital read out and the cones as a back up. Shrinkage depends upon the clay used it can be as much as 10%. The smaller the particles, like porcelain, the more shrinkage. Most of this shrinkage happens during drying, as the water evaporates, but there is still some shrinkage during firing. Cone 05 is around 1910 at final temp.

Answer 2

Electric kilns are heated by several elements located around the interior of the kiln. Gas kilns are heated by a controlled flame that is fed into the kiln from an outside gas line.

Leather-hard clay still contains a good amount of water so the shrinkage would not be very much but would depend on the kind of clay that you were using. In order to control the shrinkage, let the clay dry very slowly. Keep it loosely covered with plastic throughout the drying process.

Cone 05 is a low-fire temp and would bend roughly between 1850-1900 degrees F depending on ramp rate (rate at which you heat the kiln).

Answer 3

Kilns are heated by coils, which are nestled into the kiln walls. The peepholes (or "peeps"), are there for checking pyrometric cones during a manual firing. If you're doing a manual firing, and using cones, you'll want to be sure to place them on a shelf at the peep hole level. If you have a vent attached to your kiln, be sure to keep the peeps closed up during the firing process, and only remove one to check the cone(s). If you don't have an attached vent, you'll want to keep the top peephole open, to aid in venting.

If you're using an automatic kiln, you won't need cones--just set it an forget it :)

If you're heating to cone 05 (considered to be a low fire), the 05 pyrometric cone should mature at around 1888*F.

The amount of shrinkage in your clay is really variable. Every clay manufacturer has information about shrinkage rates, and that information is readily available from your clay dealer. Of course, that generally applies to the amount of shrinkage during firing . . .

A good way to find out how much your clay will shrink from it's wet stage to leather hard is to make some test tiles. Roll out a slab, and then cut several tiles at the same sizes. Then, check back on your tiles at regular intervals: wet (of course, this will be your original size), leather hard, dry, and bone dry. Then measure them again after your bisque firing. Track the measurements. You'll only have to do this once. After a while, you'll have a feel for how much each type of clay shrinks.

One more thing: Run a nail-sized hole through one end of each test tile. Once you get past the "shrinkage" question, use these to test various glazes, and then hang the tiles (with the help of that hole!) on your studio wall. You'll have an instant visual reference for the qualities and colors of the glazes you're using.

Good luck to you! Happy potting!!!

Answer 4

Kilns are NOT "heated" through peep holes. The holes might more be considered PEEK holes, so one can check the work, and the CONES during a firing.

My kiln is/was as large as a 55 gallon drum and fired as high as I could crank it up.

Shrinking and LEATHER hard? Hmm. If the piece is allowed adequate drying time before firing the shrinkage will occur then, and I'm confused about your word Leather. If a POT is crafted properly it likely should feel more like satin when dry, to rub a hand over.

NUMBER: 010 TO 3 - Made as a regular series (red, iron-containing cones) and as an Iron Free series for use in reducing atmospheres. These cones are used in the firing of craft and art bodies, for wall tile, glazes and some structural clay products. The temperature equivalent range is approximately 1600-2150F (890 to 1170C).

Steven Wolf