USE, CARE AND FIRING OF KILNS
By Bonnie Crandall
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| SELECTION OF KILN |
Whether you buy a used or a new kiln is your choice.
I have had both and see no difference in the use of them.
The only possible difference might be the newer computer
controlled kilns, which I understand are really the way
to go, now-a-days. Since I don't have one of that type
of kiln, this will refer to the kiln with or without a
kiln sitter.
The difference in price of a used kiln vs a new one can
be the determining factor in kiln selection. If you find
a used kiln, no matter what brand, that is in general
good repair and not abused that is under $350.00 to
$400.00, you are getting a bargain. Some small chips
out of the firebrick are repairable with kiln cement.
A cracked or broken bottom can be made useable with a
kiln shelf placed over the bottom. Sagging coils can be
replaced with a little effort or even controls that are
burned out can be replaced as well as broken coils etc.
These, however, should be taken into consideration as
being a cost that will have to be born before the kiln is
entirely useable. Some people have purchased kilns and
are using them with the coils sagging badly and seem to
be satified with the end effort, but I wouldn't want to
use a kiln in such a state due to the possiblity of
fire. Plan to have a kiln repaired where it is necessary
or do it yourself if you have that ability.
A new kiln does not have that problem but it has to be
fired first which I will approach later.
You should have the following included with the kiln you
purchase, if at all possible. The kiln itself, peep hole
plugs, shelf or shelves if it has the capability of space
enough for this item. If it has a sitter, it should also
have the gauge for it (a little round piece of metal that
has funny looking cut outs and a hole in the middle.)
Cones if possible.
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| GETTING THE KILN HOME |
Most of us face the problem of transporting the kiln
after it is purchased. When it is a used kiln, bear in
mind that the brick will be very soft and it will need
to be handled very carefully to avoid damage to the brick.
If it is set up in sections (called collars) you can
move these very successfully. If it is a one piece kiln
and fairly large, it will be heavy and you will need a
strong back or several strong backs if it is very large.
Be careful also to protect the kiln sitter and the
control knobs to avoid having to replace them due to
breakage. Perhaps most important, if it has a sitter
put the gauge in place across the two bars and be sure
the rod is through the hole in the center of the gauge.
This will prevent the rod from getting bent and also keep
the setting intact. Use a rubber band or string to hold
the gauge in place, put the rubber band across the two
bars and that will hold the gauge in place.
Set your kiln up in an area that is well ventilated or at
least has possibilities that can provide ventilation with
little expense, perhaps a garage would be suitable where
it has ventilation, and is not next to flamable products.
This is also good policy for the new kiln. Do be sure
that if it has no stand to set it up off the floor.
This is a safety measure to prevent floors from
overheating, also lots easier on the back.
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| CHECK ALL SWITCHES |
After you have the kiln set up, check again, all switches
and coils to assure that they are all in working order.
(It is to be assumed that you have done that before you
purchased the used kiln.) If all are in working order,
the next step is to thoroughly vaccuum the kiln. Let your
vacuum suction do the work, don't scrub at the fire
brick you will damage it if you do. Remember, it is
very soft and damages easily. Be sure that the peep
holes are easy to both see in
and use. If you have no sitter, you will certainly
want to be able to see the cones as you fire.
If you have a sitter, timer, you want to check to see that
it is set correctly. Again put the gauge into place and
check to see that the rod is centered correctly. If
not,there are a couple little screws on the outside of
the kiln that permit you to adjust it. Also check the
rod to see that it isn't bent. If the rod is bent, you
need to replace that, if the ceramic tube the rod sets
in is broken, that needs to be replaced. It is to be
hoped you received the instruction book that came with
the kiln, not to worry if you didn't, you will soon
learn how to operate the kiln without it.
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| TEST FIRE YOUR KILN |
Place a cone in place, either in the sitter or in a cone
holder and turn the kiln on its lowest setting. Let the
first set of elements come on and heat up. Kilns have
several sets of elements, unless they are the little
jewelry kilns, These come on in rotation depending upon
which switches are used. I would say leave the lowest
setting on at least 1/2 hour, then go to medium, if the
kiln has that setting for the same time and then to high.
You should be able to see the cones bend or hear the
sitter turn off at the end of about 1 1/2 to 2 hours
maximum. A lot depends upon the size of the kiln.
Check during these firing times to be sure you don't
have spaces between collars that you can see the heat
and color as it rises. This doesn't usually mean that
the kiln won't get hot enough to perform the firing,
just that it will take a lot longer. Every collared
kiln has a set in the fire brick and you should check to
see that you have the collars set as nearly as they were
as possible. Also the kiln should be level, collars fit
better and the possiblility of something tipping over is
eliminated.
You should do several firings. One at the most used
china painting
cone, ie: 018 or 017. The next at 015 or014 and the
final at the highest temperature the kiln is rated for. This will set the
elements into their grooves properly. Also this will
burn off any oils collected on the elements. This
highest firing should be done periodically to prevent
the elements from sagging. The oils used by our china
painting do collect on the elements and cause eventual
sagging of the elements.
If you have sagging elements, turn that element on and
let it get red, then carefully using a pair of long nosed
pliers in each hand, scrunch the element together a bit
so it fits back in the groove. DO NOT USE PINS TO PUT
THE ELEMENT BACK IN PLACE. This shortens the life of
the element by about 1/2.
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| READY FOR USE |
When you have ascertained that all is well with the way
you have set up the kiln and everything is working
properly, you are ready to use it to produce that
masterpiece.
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| THE NEW KILN |
Having made that decision to purchase a new kiln, the
next problem is which kind!! I have owned both three
new kilns and a used one. The used one was in sad shape
having been used in a city recreation situation. By
doing extensive rewiring and replacement of switches
by my talented husband we were in business. We also had
to put a shelf in the bottom to replace the broken
bottom of the kiln. When I purchased the first new kiln
a decision was made to make it a Paragon. The next two
were and are Paragons. I like the ease of firing a
Paragon, but I have also had good luck with a Cress and
a Knight, so whatever you decide as to brand it is all
up to you. There is practically no difference in
operation and satisfaction in kilns.
At any rate, your new kiln will be shipped to you in a
wet state. That is the brick will be damp to prevent
damage in shipping. You need to set your kiln up
wherever you are going to use it and prop the lid wide
open to dry it out for a couple of days before you fire
for the first time. Again, check the sitter (if you
have one) to be sure the rod is centered correctly.
Also be aware the two bars of each side of the rod
are removable. One postion gives you a lighter firing
and the other a harder (higher temp.) firing.
If you think your kiln is not firing hot enough, simply
remove those little bars and turn them over. If however
it is too hot, perform the reverse procedure. Do be
sure to coat the rod and the two bars with kiln wash to
prevent sticking of the rod to the cones.
Do this periodically also.
Place a cone maybe an 020 or even an 018 across the bars
making sure the rod comes down in the middle of the cone.
This loads the cone on the sitter. The latch, similar
to a gate latch is on the outside of the sitter and that
should hook to hold the cone in place. If it doesn't
hook, your sitter is not properly loaded. The latch
mechanism will also lift the rod so you can place the
cone under it. It is fairly simple to operate. If you
have a book that came with the kiln, it shows in
illustrated samples just how to do it.
Having loaded the cone in the sitter you are ready to
fire. Turn the knob or button on to low and prop the
lid open about 1 to 2 inches and let it heat for about
1/2 to 1 hour, then go to medium for the same length of
time and then to high. Depending on how long you stay
at each setting you should be able to fire the kiln in
about 1 1/2 to 2 or 2 1/2 hours, maximum. This will
also depend on how hot you fire your kiln. If you are
able to fire to a porcelain setting, it will take longer
of course. I fire porcelain bisque on 2 hours on low,
2 hours on medium and about 2 hours on high. The sitter
usually kicks off at about 6 hours. When doing a first
fire, you don't need to temper anything as more than
likely, the kiln won't have anything in it. You are
only firing to set the elements and dry out the brick
this first time.
The cones should be bent in approximately the center and
should not have breaks in the cone on the bottom if
your kiln is firing properly. Too hard a firing will
result in a torn looking cone and this means it is
overfiring. Under firing is a cone that is not bent at
all. Sometimes this happens if you set a limit timer
and for some reason forget to advance to the next
setting of your elements.
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| FIRING WITHOUT THE AID OF A SITTER |
If you opted to purchase a kiln without a sitter, you
will need to do the same process, but you do need to use
a holder that will hold three cones. At least at first
you need to be sure that the kiln is firing properly.
You will need not only a cone that is rated to the
temperature you really want, but also a cone that is
one setting lower and one that is one higher. The first
witness cone should be completely bent over the main
cone should be bent at what I call the waist, halfway,
and the third one barely bent, like it is tipping its
hat. Practice is what this process takes, you will soon
be able to tell what the cones should look like. After
much practice, you will probably be able to dispense
with the witness cones, but those are always a good
safety feature and sometimes prevent overfiring.
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| USING YOUR KILN |
I am assuming that you have coated the kiln bottom and
shelves with kiln wash. Vacuum at least every other
time you use the kiln. Don't let it set open, it
collects dust just like furniture does and you don't
need extra dust on the painted ware. Keep an eye open
for any oddities that happen during firings, if
something happens more than once check to be sure
everything is still okay before using again. You will
have variences in times for firing. Sometimes a damp
day can make the time a little longer or perhaps it has
been a drizzily week and the brick has absorbed a little
moisture etc. Lots of variables. Also watch for sagging
elements. Correct these when they first start and it
won't be such a job. No matter what anyone says, these
are not really safe and besides they take up precious
space in your kiln.
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| JEWELRY AND FAST FIRE KILNS |
These I don't know too much about, having never had one.
I have been present at seminars where the teacher used
these and have often thought I would like one, but
haven't been able to spring the bucks to purchase one.
Since I don't regularly do small items, I don't really
feel the need to own one. I do know that the teachers
seem to be able to really pack them for seminars. Many
come with sitters on them and I think I saw an ad for
one with a limit timer as well. Pretty handy. some
even have more than one setting on the switches so that
again is at the discretion of the purchaser. Be advised
that they won't permit large items due to the interior
limits on space. The brick, for the most part, are
almost as thick as the larger kilns and the interior
of these are in miniature proportions.
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| NOVA KILN |
I don't know if this one is still around, but I had the
opportunity to see this kiln in action. It was one of
the fastest kilns I ever saw. It fired to an 015 in
just 1/2 hour. It operated on 110V but I think I heard
it soon burnt out and just didn't stand up. It might
have been the precurser to some of the fast fire kilns
we have today.
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