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For hot glass artists, the decision to purchase a
kiln is a major commitment to the art form.
It is very important the artist chooses the correct kiln for their
needs. However, this purchase
is normally met with trepidation because many artists are not familiar
with electric kilns. They have
natural fears of things hotter than the kitchen oven.
The purpose of this is to familiarize warm glass artists with the
types of kilns and their features as well as relieve some of the
trepidation.
Safety is of course a top concern for the user as
well as the manufacturer. Most
of the manufacturers of kilns have been building electric kilns for over
twenty years with some for as many as 50 years.
Most of the kilns manufactured are certified to Underwriter's
Laboratories (UL) specifications or equivalent testing agency.
UL is the organization that tests household electrical appliances
for safety including toasters, hairdryers, lamps, etc.
If the artist follows the instructions of the manufacturer, there
is almost no chance of a hazard. Use
common sense. The kiln is hot
so do not leave flammable materials close, do not permit children to play
unsupervised nearby, etc.
The next section will discuss selecting the right
kiln for the artist. This is
very important as the kiln needs to serve your current needs as well as
the needs of the near future. They
are a serious investment and time spent during selection will prevent
headaches later.
- KILN
SELECTION: The
primary criteria for choosing a glass kiln are type of controller,
size and quantity of the pieces fired, and types of techniques
used.
- Types
of controllers. There
are three types of controllers used in glass kilns: infinite
switches, simple digital controllers and professional digital
controllers. The smaller
simple kilns designed to plug into normal household outlets tend to
have infinite switches and simple digital controllers while larger
and sophisticated kilns tend to have the more sophisticated
controllers. Therefore
the type of controller that is standard on a kiln is what is
appropriate for the kiln design.
i.
Infinite Switches:
There are controllers with knobs similar to electric ranges or
stoves with low, medium, high or numbered 1-5 etc.
These are very basic and inexpensive.
They do not control the temperature of the kiln, they only control
the amount of time the elements are actually on.
They should be used in conjunction with a pyrometer, which is a
stand alone device that accurately measures the temperature inside the
kiln. Infinite switches are
not good at controlling the temperature of a kiln during a hold cycle.
Very good for small quick projects.
ii.
Simple Digital controllers:
These are designed for beginner to intermediate experience
glass artists. The controllers
can be programmed to heat up, hold, and control the cool down rate for
annealing then turn off automatically.
They make firing glass projects very easy.
These digital controllers tend to have few diagnostic tools,
ability to store only one program, and few advanced options for more
advanced techniques. They are
relatively inexpensive and easy to use for the novice to intermediate
glass artist.
iii.
Professional Digital Controllers:
These are designed for the intermediate to professional level
user. They are more complex to
program, offer a wide array of diagnostic tools and advanced options for
perfecting the firing, and generally a connection for use with a computer
interface. These generally
have up to 20 segments, ability to control for thermocouple drift, storage
of multiple programs in memory, and extensive diagnostic messages.
- Size
of the Kiln. The
size of the kiln should be based upon the size and quantity of
pieces fired, the types of techniques used, and the power available
to the user.
i.
Size and quantity of pieces.
Analyze the type of glass art you want to make.
Is it 10 inch plates, tiles, vases, jewelry, made with molds, etc.
Check the sizes of the pieces and their layout in the kiln.
They should not be loaded closer than one inch from the side
elements. How many pieces do
you want to fire at one time. Look
at the usable space of the kilns. Round
kilns give the best space for the money.
If only firing small pieces or you want a to test colors and compatibility, look at small fast test kilns so you do not need to fire a
large kiln just to test glass.
ii.
Power Requirements.
The larger the kiln the greater amount of power is required to
operate the kiln. Before
purchasing a kiln make sure you understand the power requirements, volts
and amperage that is available in the location for the kiln.
Small kilns can operate on 120 volts whereas most 8 sided and
larger square kilns operate on 240 volts and may require up to 50 amp
service. These kilns usually
require the services of a licensed electrician for installation of special
receptacles and special wiring. This
will obviously add to the cost of purchasing a kiln.
Consult an electrician and the manufacturer for the exact
electrical specifications for the model you want to purchase.
Wrong voltage is the number one mistake made by customers when
ordering a kiln. Make sure the
service is 208 or 240 volts, the wiring looks exactly alike.
- Top
and/or side elements.
i.
Top elements.
This design has been in existence for many years. The
benefits of this are it evenly heats flat glass.
Glass does not like to have temperature differentials across it or
it will break. If you heat
from the sides only, the outside edge of the glass will heat faster than
the middle. This is fine for
very small pieces and jewelry work, but not for large, thick pieces.
ii.
Side elements.
Side elements are needed to improve the uniformity of the heat
distribution in the kiln for certain techniques such as firing tall molds.
Some small kilns will have only side elements.
This is fine for small pieces and jewelry.
iii.
Side and top elements.
Many designs come with both top and side elements so they can be
used in a variety of techniques. Again
these kilns tend to be more expensive and larger.
- Front
load or top load. Kilns
come in two basic designs either a polygon that opens in the top
like a washing machine or a square design that opens in the front
like a microwave.
i.
Polygon top load kilns are very
economical for their size. They
are a proven design over many years. They
will fire most types of glass projects very efficiently.
Main drawback is they are not conducive to techniques that require
the artist to manipulate the glass when it is hot as when the user opens
the lid all the heat is released at the user.
This is much hotter than removing cookies from the oven and is a
safety hazard. Many of these
are made as either top only or top and side element versions.
ii.
Front loading square kilns.
These kilns are designed for more professional or advanced users,
especially for the user to manipulate the glass while hot.
When the door is opened, the heat escapes up and the user can
manipulate the glass easier with less direct heat in this kiln design.
These are designed with door safety switches that turn off the
elements when the door is opened. These
also are designed to permit the user to adjust the amount of heat from the
top elements and from the side elements using the infinite switches
depending upon the technique.
I hope this introduction to kiln selection assists
you in taking the warm glass art to another level.
As always, if you have any questions please contact us as we will
be more than happy to assist in selecting the right kiln for your
application.
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here to go to Paragon's web site.
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the page on Basic Fusing and Slumping.
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