Due to gas flow,
the tank may have a tendency to freeze solid. If ice is observed forming
on the outside of the tank, water can be run over it to help keep it
melted. The tank can also be lowered into a large bucket of warm water.
A larger burner
orifice in necessary when used on household gas pressure of six (6) to
eight (8) inches of water column. If your kiln was ordered for use on
household natural gas, it is equipped this way.
ventilation is required when firing your gas kiln. Vents for Olympic
Torchbearer kilns, if fired inside, may be purchased from Clay-King.com at www.clay-king.com/ventpage.htm.
Olympic Raku kilns are usually fired in a garage or outside due to the
raku process and therefore do not require a vent.
DownDraft kilns, you may create your own vent by purchasing sheet metal
from a local heating and cooling manufacturer. Shape the sheet metal into
a cone shape 36" wide in diameter. The vent should be placed 18"
above the kiln top – center on the stack (damper opening) with an
exhaust pipe 10" in diameter that is determined by ceiling
construction, double walled if combustible
ASSEMBLY OF RINGS
FOR TORCHBEARER KILNS:
your new kiln rings, always be sure to grasp the rings by the outer
surface only. Do not grasp the bricks as they are made of a porous
material and may chip in your hand.
certain the stand is level, adjust the burner manifold so the pipe section
on top of each air mixer is approximately ½ inch below the bottom of the
kiln. The kiln bottom must be positioned on the stand so each burner is
directly beneath one of the holes. It is recommended that the burners be
positioned with the gas valve on the right side when you are facing the
kiln, however, if it is more convenient to place the manifold in another
position be sure to align the burners with a hole in the kiln bottom.
The kiln rings
may now be stacked with the hose clamps in back and the observation holes
aligned in front. If the kiln has the optional automatic shut-off system
the ring with this device should be placed in the middle of the kiln to
insure accurate results. Once the kiln is assembled, be sure the inside is
clean and free of dust. It may be necessary to vacuum the inside of the
kiln at regular intervals.
Once the kiln is
hooked to a gas source, each burner may be ignited and the primary air
adjusted for each of the air mixers or burners. Loosen the locking screw
before attempting to adjust the burners. The locking screw needs not be
retighten unless the kiln is being moved.
Air adjustment is
very important and should be accomplished with care. The air adjusting
plate is locked between the burner orifice and the burner. The burner must
be loosened slightly from the brass orifice, which threads into the center
of the burner, to move the air adjusting plate. After loosening the
locking screw and the burner from the orifice, rotate each plate to insure
it will move freely. Next position each air adjusting plate so the air
inlets are 50% open. The kiln may now be ignited and the fine air
adjustments can be made.
adjusted kiln will have all flames uniform in appearance with the
transition from candle flame to intense flame occurring at the same time
for each burner as the gas valve is opened. The kiln operates most
efficiently when the intense flame has a maximum of blue color. If the
flame tends to blow out when the gas valve is opened the air inlet should
be closed slightly.
adjustment of the burners need not be changed once the optimum settings
are obtained; however, reduction firing in the kiln may be accomplished by
closing the air inlets. The easiest and most reproducible reduction is
done by dampering the vent hole in the lid and will be explain more
thoroughly within this document.
& THERMOCOUPLE SAFETY SHUT-OFF:
The ignition ring
is used to:
multiple burner system from one point
flame on each burner
burner that may extinguish
safety shut-off is used to:
To operate the
ignition ring, depress the red button on the top of the magnetic valve and
light the ignition ring. The small gas valve on the ring should be
adjusted to allow sufficient gas flow to propagate a flame entirely around
the ring when it is ignited at any point. Once the ring ignited the
thermocouple on the ignition ring is hot and the valve will stay open by
itself (approximately 60 seconds is required).
The burners may
be lighted by turning the hand valve on the burner manifold.
LOADING THE KILN:
Olympic gas kilns
are noted for their multiple burners, which are spaced around the
perimeter of the kiln. All shelves and ware should be loaded inside the
burners and spread one (1) inch apart to insure even heating. A shelf
should be placed three (3) inches above the kiln bottom. Each additional
shelf should be supported by posts that are placed directly over the ones
below. All shelves should be turned over every other firing to prevent
excessive sag and the larger shelves should have a support in the middle.
This is especially helpful for the bottom shelf.
firing schedules are recommendations and should be considered a starting
point for the method eventually adopted by the user of the kiln. Each kiln
has its own individual characteristics that may be influenced by location,
gas pressure, gas flow, weather, and the potter’s own individuality. The
user of a gas kiln needs to be willing to experiment with different firing
techniques in an effort to express his/her own theories and develop
methods which prove most satisfactory for the user’s own unique
schedules need to be adjusted to conform to the thickness and mass of the
ware being fired and the load density of the kiln. The more pieces the
kiln contains the slower it should be fired. Finally, the clay body must
be considered, remembering its strength, reaction to thermal shock,
Dry the newly
formed ware at room temperature until it is no longer cold to your sense
of touch. Smaller pieces need seven to ten days drying time and larger
pieces 10 to 15 days. Bisque of pre-firing is necessary to pre-condition
the ware for glaze application and glaze firing. Bisque firing is a slow
firing in which the physical and chemical water is driven off and the body
becomes hard and solid. The ware is most susceptible to cracking during
the early stages of bisque firing and several temperature zones should be
crossed with extreme care.
water leaves the clay at 212° Fahrenheit and the chemical water is driven
off from 350° to 500° F. At 1073°F the quartz
inversion occurs causing a size change in the body of approximately 2%.
burners and adjust the gas valve to allow the flame to burn with a
candle flame for 30 minutes. The pre-heating period should be extended
if thick walled pieces are being fired or the kiln is densely loaded.
Some soot may be observed during the candle flame period; however, it
will burn out when the kiln reaches higher temperatures.
Open the gas
valve enough to increase the length of the candle flame and cover the
top port about 80%. Leave the kiln in this condition approximately one
Turn up the
gas to allow the flame to burn with more force and with little yellow
color. Open the top port about half way. After several hours at this
rate open the gas valve half way. Leave the kiln at this rate for two
hours or until the inside coloration is a dull red.
ware has padded through its critical point, which indicated, by the
dull red coloration, the burners can be turned up all the way and the
top port can be completely opened.
When the cone
has bent and the kiln has shut-off, cover the top port and plug the
The kiln should
be warmed up with a slow flame for about one (1) hour. The flame can then
be gradually increased at will until it is fully on. When kiln is fully
on, the top port should be completely open. After the desired temperature
has been reached, leave the kiln on for at least an hour at that
temperature to properly soak the ware. Shut the kiln off as before, plug
the observation holes and cover the top port. For best results do not
reopen the kiln for 24 hours.
The easiest way
to obtain reduction effects is to wait until the kiln is near cone 9 and
then cover the top port about one (1) inch. Wait for 30 seconds and watch
for a slight flame coming from the top port and observation holes. If no
flame is seen, cover another ½ inch and wait for the flame. Keep doing
this in small increments until a slight flame is seen. Leave the kiln in
this condition for about one hour then take the top port cover off
completely and bring to final temperature. It is important to remember
that over reduction will drop the inside temperature considerably and
waste both gas and time.
When firing with
propane the flame is always evident at the top port. Turn the gas down a
little if less flame is desired.
may be accomplished by heating the kiln to cone 05 with top port open. At
cone 06 cover the top port with the brick provided until the flame is
evident from the top port and observation holes. The reducing atmosphere
should be maintained for 30 minutes then the brick covering the top port
should be pulled back until only an occasional flick of flame is seen from
the observation holes. The kiln can then be heated to cone 9 and an
additional reduction can be done as described above. A slightly reducing
atmosphere from cone 06 to 9 will insure that the effects of the body
reduction are not lost with additional heating.
containers that are the correct size (arrange for easy access and
clear movement around the kiln)
should be at a safe distance form the kiln, yet easy to reach during
post firing process
know their job
sources for cooling and emergency situations
clear avenues for unencumbered movement
Turn on the
and light each burner or if kiln has ignition system push (red) button
while lighting pilot bar (bar that runs underneath the kiln) until the
flame holds. After ignition system is lit, burners will light
gas valve (blue or red valve controls gas to burners). When the gas
valve is perpendicular to the bar, gas is allowed to flow to the
A pyrometer will
greatly enhance your efforts during the raku process. As the kiln reaches
approximately 1800º Fahrenheit begin loading your ware. Slowing lower the
raku drum in 10-15 minute intervals to allow pottery to get use to the
thermal shock until drum is completely closed. Around 1900-1950º F the raku process will begin to take place. You can tell the
ware is ready to remove by its shiny, wet appearance. Raise drum, remove
pieces and place in reduction containers as quickly as possible. Once ware
is inside the container add more reduction material and cover within 15
seconds to ensure efficient smoking. (It is not how much reduction
material you use, but how fast you can get pottery into the container and
covered that provides exceptional raku pieces.) Keep container covered for
15 minutes - 1 hour.
kilns are designed to maintain their temperature (even when drum is
lifted) so that you can continue the raku process without interruption.
Once ware is removed from the kiln to be placed in reduction containers,
new items may be loaded in the kiln. You may also want to place items on
top of the raku drum (on the outside) that you will raku next so
that they are warmed up before placing in the kiln.
pyrometer used with kiln firings is similar to the speedometer in your
car. The pyrometer shows how fast temperature is raising or lowering in
- Kiln will have a hole punched
out of the skin of kiln.
- Drill a 5/16-inch hole through
the kiln wall and insert the thermocouple from the pyrometer into the
- Pyrometer will show how fast
temperature is rising or lowering in the kiln
The automatic shut-off system is
used for accurate and worry free bisque firing and as a safety device when
doing reduction firing. The system consists of a Dawson Automatic Kiln
Sitter and an electric solenoid valve. When the kiln is assembled the
solenoid valve will be on the right side as you face it. The cord from the
solenoid valve on the burner system is plugged into the receptacle on the
electrical box housing the kiln sitter. The electrical box on the kiln
must be plugged into a 120-volt wall outlet. Before using the kiln sitter
read the instruction manual for the kiln sitter that accompanies kilns
purchased with kiln sitters.
To Initiate the Gas Flow:
Place a cone in
the shut-off as outlined in the kiln sitter instructions and depress the
button on the kiln sitter locking the cone in. Press the small black
button below the kiln sitter to activate the relay system and open the
solenoid valve allowing gas to flow to the burners.
If electricity is
lost during the firing the kiln will automatically shut-off. To re-ignite
the kiln when electrical power is resumed, press the black relay button
and light the burners. Anytime the kiln is ignited the gas hand valve
should be opened only enough to light a candle flame. The coil of the
solenoid valve may emit an audible buzz. This is a normal occurrence and
is simply a 60-cycle hum.
To bisque fire
with the automatic shut-off system use the desired cone in the shut-off
device, fire to maturity, and the kiln will shut-off on its own.
The kiln sitter
is a safety device when doing reduction firing. A cone one or two numbers
higher than the cone used for reduction end point should be placed in the
shut-off. If the kiln is not manually turned off at the conclusion of
reduction firing, it will shut-off on its own before damage from
electronic wall unit features programming by cone number or segment method
allowing you to create your own programs. Each program has eight segments
with ramp/hold profiles and controlled cooling rate. The controller also
features a delay start for firing, numerous means for diagnosing problems
and convenient program review before or during a firing. Olympic’s
electronic controller on its gas kilns requires that the operator manually
manipulate the gas valve while the controller runs the kiln. Because the
electronic controller runs on an on/off mode, the gas kiln operator will
need to adjust the gas flow accordingly.
mount control vertically to wall.
valve from the gas kiln ignition system into the wall unit.
unit into power source.
5/16" hole through the kiln wall and insert thermocouple from
wall unit into the kiln.
electronic control instructions thoroughly and following programming
instructions that best suit your firing requirements.
Once you are
ready to fire the kiln follow the instructions for operating the ignition
Turn wall unit on
and hit Start. Slowly begin opening gas valve. As temperature increases
within the kiln, continue to open gas valve as needed.
WHAT TO LOOK FOR
WHEN YOU HAVE PROBLEMS FIRING YOUR KILN:
Bottom is Hotter
Than the Top of Kiln
backpressure. Top port cover is closed too much.
inside the horizontal air mixer tube*.
plate is not opened enough.
Top shelf is
too close to the top port.
Kiln Does Not Get
Hot Fast Enough
plate is not opened enough.
is not adequate which other gas appliances being used at the same time
inside the horizontal air mixer tube*.
– excessive reduction drops temperature considerably.
is too small for the gas pressure being used.
*Note – A good
test to see if the gas is burning in the horizontal air mixer tube is to
insert a broom straw about half way into the tube from the primary air
opening. If the straw comes out burned the gas mixture is burning inside
the air mixer. This condition is not dangerous, but will make it nearly
impossible for the kiln to reach high temperatures. Turn the gas off and
slightly increase the amount of primary air in the opening, then re-ignite
to correct the problem.
PROPANE TO NATURAL GAS:
If a conversion
from propane to natural gas is made, the following table shows orifice
sizes for each Olympic kiln.
The burner system
on a 27-inch deep kiln has sufficient power to allow the addition of extra
rings to the kiln without burner modification. The actual gas connection
may be made with flexible ½ inch gas line used in the installation of gas
dryers or the kiln may be piped directly into the gas line with a ¾ inch
black pipe. If
a conversion from natural gas to propane is desired,
please contact Olympic Kilns at 800-241-4400.