Frequently Asked Questions

Kiln choice:

What voltage do I choose, 208 volts or 240 volts

Most residential sites are supplied with 240 volt electric service. Many older buildings and industrial sites are supplied with 208 voltage. 208 or 240 volt power is not your choice. Rather , you are obliged to discover which is present where you choose to set up your kiln. You may look at the label on other appliances with larger motors to discover the voltage source. With an inexpensive meter, a user can measure the voltage where another appliance is plugged in. If an electrician has worked at your site, he can inform you.

Which phase: Single or Three Phase

Industrial sites often present an option to chose 3 phase power. There is an economy in 3 phase power, however, it increases initial cost by approximately 200 dollars. On a 240 volt kiln that draws 50 amps, ie: Skutt 1027, a ten hour firing costs about 25 dollars. If there is a ten percent savings using three phase power, roughly 80 firings would be required to reacha breakeven point.

Which brick size:

Standard size bricks are 2.5 inches. And heavier bricks are 3 inches thick. The latter are more insulating which means lower firing costs, and slower cooling. The choice of the thicker brick also means that the firlng Chamber diameter will be reduced by 1 full inch.


Fumes from kilns are undesirable. Vents are available costing approximately 350 dollars and are easily installed. Earlier vents featured the fan motor under the kiln. Newer ones are mounted on the wall with only the vent tubing connected to the kiln.  This design removes the vibration of the motor from effecting y our firing.  Kiln vents assist in creating an even firing and exhaust fumes.  Click here for more information


If your kiln will be delivered from a distant supplier via a common carrier, than you must consider how to get it off the truck and to its final location. Skutt kilns and other sectional ones can be quickly and easily disassembled even on the truck at the time of delivery. Sections have handles and simple latches. If your kiln comes with a digital controller, you may need a screw driver to remove 4 screws fromf a hinged box on the side of the kiln. The box can then be removed from the kiln. The wires within are numbered and easily separated via spade connections. If you purchase a kiln that is not sectional, lift gate delivery is an option for approximately 50 dollars, but you will still have the problem of maneuvering the kiln to its final location!

Firing Range

Three firing ranges are common among potters: Low Fire, Mid Range and High Fire corresponding roughly to pyrometric equivalent cone 06 through cone 04, cone 6 through cone 8 and cone 9 through cone 11. These designations in degrees are roughly 1830 to 1920 degrees Fahrenheit, 2150 to 2250, and 2280 to 2330 respectively.

The Low firing range is characterized by bright colors. Glazes prepared for this interval include rich reds, oranges and yellows. There is an economy in firing at a lower range, as less power is required to reach maturity.

The Mid-range allows production of more durable ware, and affords the opportunity to choose glazes with a mottled or textured image. Porcelain clays are also available in this range. This interval is well within the range of electric kilns.

The high fire range is associated with reduction firing in gas fueled kilns. By controlling the oxygen flow into these kilns, magical earthy glaze effects are possible. Colors tend to be muted. High firing is also possible in electric kilns, but glaze possibilities are not significantly different then those in the Mid Range. Furthermore, the cost of firing is greater, and kiln element life is reduced.


Moist Clays

All of our clays pass through a mixer and a de-airing pugmill, which renders the clay ready to use without wedging. Clay is packaged in 25-pound plastic bags, two such bags per 50-pound carton.
In addition to our house formulae, APS can mix clay to your formulation. Minimum quantities vary from 500 pound to 1000 pounds depending on the ingredients in your blend.
Samples are available at the cost of UPS shipping. Charges on a 25-pound sample amount to approximately eight dollars.

Shipping Clay

For orders of 300 pounds or less, UPS offers an economical choice called "100 weight plan". At the 500 pound level, commercial trucking is often a good choice. Within a 250-mile radius, such orders take only one day. The driver is responsible only to bring cargo to the rear of the truck. He may assist after that point but is not obliged to do so.
If next day arrival is not required, our own truck is a good option. Our driver will assist with unloading, and we have a tailgate to facilitate the process. Generally, a one-week lead-time allows an adequate interval to fill orders.

Clay Range

Three standard firing ranges are low fire, mid range and high fire with recommended firing intervals of cone 06 - 1, cone 5 - 8 and cone 8-11 respectively. The low fire range is characterized by richer red clay bodies and affords choice of glazes, which are brighter in color, particularly reds, oranges and pinks. Mid range clays are harder but not compatible with these bright colors. On the other hand, the mid range does allow a mottled or textured glaze finish. In the high fire range, hardness is an incentive. In addition, for those with access to a gas kiln, reduction firing is possible which allows for a magical earthy range of glaze results. The high fire range is not common for electric kiln firing.

Clay Types

Sculptural clays are better suited for hand building and tile tasks. They have an abundance of larger particle size clays and/or grog or sand to facilitate drying without cracking the ware.

Low Firing clays are prepared with and without sand or grog. Clays used for hand building are typically subject to more stress and benefit from the presence of grog. Sand is often used with white clays since it is lighter. Sand and grog help clay bodies to resist cracking while drying by providing a less dense clay blend through which air can more easily escape from the ware..

Mid range clays are harder than low fire clays fires. This range does not support the bright colors of the low fire range, but it does allow glazes with a mottled or textured appearance.

High Fire stoneware's contain ten percent of a fine grog excepting White Stoneware which is prepared alternately with sand. Mid range White Stoneware's share this option.

Self-Hardening clay dries to a light beige color and hardens in one to two days producing a durable surface. Pieces produced this way may be decorated with acrylic paints.


The hazard of clay derives from the dust of clay. Free silica, present in clays and glazes in dust form exists in a very small particle size which upon prolonged exposure, can build up in the lungs. It is important to reduce the presence of dust in the work area and to consider a proper dust mask rated for clay dust when a dusty environment can not be avoided.

Metals, such as selenium, cadmium, cobalt, copper which are common in glazes to produce color, are harmful if inhaled or ingested. Some glaze materials are soluble or subject to leaching out in certain environments. A pitcher of juice standing a long time where the glaze contains soluble ingredients can pose a safety issue.  More information is available through material safety data sheets, accessible through your supplier.

Call us at Amherst Potters Supply with further questions: 413 586 4507.

Amherst Potters Supply, Inc.
47 East Street
Hadley, MA 01035

Phone 413.586.4507
Fax 413.584.5535

All contents ©Copyright 1996-2011 Amherst Potters Supply. All Rights Reserved. Last Updaated January 16, 2011