INTRODUCTION
During the
initial firing of the kiln, the refractory insulation will shrink approximately
5%, due to a portion of the silica micro-fibers that comprise the insulation
being fused together by the heat. A break-in procedure will be outlined later
in the instructions during the initial firing of the KK-6.
The
Alumina Silicate Refractory insulation is not degraded by the flame alone.
However; the insulation is susceptible to erosion by spilled borax. Borax is a
common component of most all of the fluxes used in melting and assaying, so
care must be taken not to spill borax flux onto the insulation. Methods for
repairing and stopping any spilled borax from fluxing the insulation will be
outlined in these instructions.
MELTING
INSTRUCTIONS
Note: White flux is best for
melting silver or copper / Black flux is best for melting gold.
1. Place
the Kwik Kiln on a sturdy, level, fireproof surface. The kiln is a modular
design and comprised of three pieces; the base chamber, the upper chamber and
the lid. The upper chamber and lid are removable together or separately and
allow for easy loading and removal of either mini or A0.5 crucible. When
stacking, always align the clamps with the bolts in the same direction, as the
stainless steel jacket is approximately 1/8” shorter than the width of the
insulation. This allows for insulation to insulation contact of the components,
when the kiln is stacked correctly. Remove the lid and body and place the 1”
ceramic pedestal centered in the base portion of the kiln. The pedestal is
where the crucible sits during the firing. The pedestal also helps to deflect
the flame from the burner away from the crucible, thus preventing rapid thermal
expansion from cracking the crucible due to direct contact of the flame.
2. Align
the torches with the side ports and gently insert the torch tips approximately
one fourth inch into the side ports of the Kwik Kiln. Secure the torches with a
suitable device, to prevent the torches from rolling and to ensure that the
valves and tips are parallel with the surface.
3. Remove
one of the torches and light it. Re-insert the torch gently into the side port
of the Kwik Kiln and light the second torch. Once both torches are lit, replace
the body of the kiln and the lid. Allow the Kwik Kiln to warm up to a bright
orange, while preparing your crucible melt. You should have a flame
approximately 2” to 4” tall exiting the top port of the lid when the kiln has
warmed up.
4. Preheat
your crucible by placing it on the lid of the kiln while the kiln is warming up,
to help minimize thermal shock when placing the crucible into the kiln. After
your gold or silver has melted, allow the crucible to remain in the Kwik Kiln
for a few of minutes, so that it is hot enough (yellow heat) to pour into your
mold, without the metal solidifying during your pour.
5. Remove
the crucible and pour carefully but purposely into your mold. After you pour
your melt into the mold, the flux will seal the top of your melt from any
atmospheric oxygen, so that you have a shiny, un-oxidized surface when you
separate the gold or silver from the flux. We recommend always using a graphite
mold, since it readily releases your pour from the mold without additional
release agents or procedures needed.
6. Once
your pour has cooled, remove the pour from the mold and tap the flux with a
suitable tool until it comes free from your gold or silver. Be careful of the
flux spalling during this process as it can fly off the ingot with considerable
force.
Tip: If
you want an un-marked ingot, gently tap the ingot with your tool until the
easily removed flux comes off and then place your gold or silver ingot in a
glass jar of white vinegar. The flux will dissolve overnight and your ingot
will be shiny and un-marked after removing the loosened flux.
KK-6 INITIAL FIRING AND BREAK-IN
PROCEDURE
As
previously mentioned in the introduction, the insulation comprising the lining
of the kiln is composed of a micro-fiber alumina silicate refractory material.
Under a microscope, these fibers resemble quartz crystals and, when heated to
the temperatures the kiln operates at, a portion of these fibers fuse together.
When the fibers fuse together, some of the voids between the fibers are filled
with the newly fused fibers and the insulation shrinks approximately 2% to 5%.
This has no effect on the insulating properties of the insulation, however
small cracks may form in the insulation. The following procedure helps to
stabilize the kiln lining once the initial shrinkage of the insulation is complete.
As
described in Step 3, light the kiln
and let it warm up for 15 to 20 minutes. After approximately 20 minutes have
expired, you will need to tighten the stainless steel jacket, to hold the newly
tempered insulation in place and to minimize any cracking of the insulation.
Starting
at the bottom of the kiln and using a 5/16 nut driver; tighten the bottom clamp
until the clamp is snug. Do not over-tighten the clamp; all it needs to be is
snug. Work your way up the kiln, clamp after clamp, applying the same amount of
torque to all of the clamps, until you reach the top of the kiln. While
tightening the clamps, in order to hold the lid and body in place, put your
gloved hand on the outside edge of the kiln lid and hold enough down pressure
on the kiln to keep the body and lid in place while tensioning the clamps. The
lid will be hot, but if you hold down on the outside edge of the lid and keep
your gloved hand out of the center of the lid, it’s manageable.
This
procedure is simpler than the description of how to perform it and takes less
time to complete than it does to read this portion of the instructions. As you
use your kiln, it is a good idea to check the clamps tension once in a while.
After the
stainless steel jacket has been re-tensioned, turn the torches off and remove
them from the kiln. Leave the lid and body in place and allow the kiln to cool
down to room temperature. Note: Always re-stack your kiln and leave the lid and
body in place when you shut the kiln down after using it. This minimizes rapid
thermal shock from affecting the insulation.
Once your
kiln has cooled to room temperature, remove the lid and body of the kiln and
inspect the condition of the kiln insulation. Small cracks in the insulation
are of no concern and have no effect on the kiln’s performance. However, if
there are any larger cracks that you feel need attention, you can fill them
later with Liner Restore and then apply Armor Coat to the interior of the kiln.
As you use the kiln, the insulation will ‘temper’ from the heat and will
stabilize and no longer shrink, however the lining may become somewhat brittle.
That is just the nature of the beast, so to speak. So, just be aware of this
fact and treat it with care.
CARING FOR THE KILN’S LINER
Three products are supplied with the KK-6 for optimizing and extending
the life of the kiln liner: Liner Restore, Armor Coat and Spill
Stop. All three products must be kept from freezing, or they will
become unstable and unusable.
Liner Restore is an
alumina silicate based viscous material that is designed for filling cracks and
patching any damage to the liner. This material is best applied in layers and
allowed to air dry between applications. Generally the layers should not be any
thicker than approximately 1/8”, when repairing any spilled flux holes or liner
cracks. This material is tough and stable when applied properly to the liner
and helps to strengthen and armor the liner as well.
Armor Coat is a high alumina material
with the consistency of thick paint and is applied over the top of the Liner
Restore, after repairing the liner. The high alumina formulation of Armor Coat
helps resist liner erosion from the heat generated in the kiln and helps to
shield the liner from any borax flux dusting from the crucible and minor flux
spills. This material is painted onto the liner in thin coats and allowed to
air dry between applications.
Spill Stop is a water based colloidal silica solution that must be mixed with
calcium phosphate (bone ash) to the consistency of a thick paste. Spill Stop is
used when there has been spitting of flux from the crucible, or minor spills
onto the liner of the kiln. As previously mentioned, borax flux will attack the
silica that the kiln liner is comprised of. Spill Stop will neutralize it.
RECOMMENDED APPLICATION OF THE
PRODUCTS
After you
have fired your kiln a few times and the liner has stabilized and tempered, it
is recommended that you apply the products in the following manner. Assuming
that there has been no crucible spitting or spilling of the flux onto the
liner, Spill Stop does not need to be applied to the liner and you can proceed
to the Liner Restore Step. If there has been, Spill Stop is first
applied, to absorb the borax flux and stop the flux from attacking the liner
any further, as follows:
Spill Stop: Using a small, clean glass
container, pour approximately ¼ to ½ fluid ounces of Spill Stop liquid into it
(a shot glass works great). Slowly add bone ash to the liquid in the shot
glass, while stirring the contents, until you have a thick paste like mixture.
Using a small, stiff paint brush, coat the area where the borax flux has been
attacking the liner. You don’t need to fill the area completely - just coat it
well, with the Spill Stop paste. When the material dries, in approximately 12
hours, the silica is absorbed by the liner and the bone ash will absorb the
borax flux, which stops any further erosion of the liner during upcoming
firings. When you’re done with the Spill Stop, the shot glass and brush can be
cleaned up with tap water. This method can be used anytime you have any minor
crucible spitting or spills.
Liner Restore Step: Apply
Liner Restore to the interior of the kiln’s liner. Liner Restore is fairly
thick and a paint brush is not suitable for its application. It is recommended
that your wear a thin pair of Nitrile rubber gloves and apply Liner Restore to
the liner with your index finger. Rub the material into the surface of the
liner, so that it penetrates into the alumina silicate insulation and seals it.
When patching cracks and/or holes, use a gentle but firm pressure to force the
material into the crack or hole, until it fills the void.
Remember
that it is best to apply Liner Restore in thin layers, not to exceed
approximately 1/8” at a time. We recommend that you apply a thin sealer coat to
the entire interior of the kiln, using a gentle but firm pressure, then allow
the kiln liner to dry for 12 to 24 hours at room temperature. After the sealer
coat of Liner Restore has dried, apply another layer of Liner Restore to the
interior of the kiln liner, smoothing out any rough spots and completing the
filling of any cracks or holes. If you apply any Liner Restore to the mating
surfaces of the modular pieces, make sure that you only apply a thin coat so
that the mating surfaces remain flat and only fill any cracks to where they are
flush with the top of the mating surface.
Armor Coat Step: Once you
have completed the Liner Restore application, the next step is to apply Armor
Coat. Armor Coat is a high alumina material that helps to prevent erosion of
the liner from minor flux spills and heat. Armor Coat is the consistency of
thick paint and can be applied with a 1” paint brush. Armor Coat will begin to
set up fairly fast when applying it, due to the high alumina content of the
material. So, you want to move deliberately and quickly when applying it. If
the area you are applying Armor Coat becomes tacky, move on to another area to
prevent unnecessary build up. As previously recommended, two thin coats are
better than one thick one. Armor Coat will scale and crack if applied too
thickly. It needs to be absorbed by the Liner Restore, to be effective. Armor
Coat can be applied to the mating surfaces of the modular pieces of the kiln.
Just apply it thinly, so the surfaces remain flat, without any unnecessary
buildup of Armor Coat.
Clean up: All of the Liner Restore
Products are water soluble. So, if you get any of the material on the outside
of the kiln, it can be cleaned up with a damp rag. The materials clean up
easier if uncured, when cleaning them off the stainless steel jacket. When
applying any or all of the products, wear nitrile gloves. Always allow adequate
time for the applied materials to cure, prior to putting the kiln back into
use. 24 hours at room temperature is recommended.
Note: A small amount of distilled
water may be used to dilute both Liner Restore and Armor Coat, if too thick. Do
not dilute Spill Stop.
ADDITIONAL ITEMS NEEDED
Welding
gloves (recommended) or heat proof gloves
Welder’s
leather apron
Heat proof
surface upon which to work
Dust
respirator mask
Clear
safety goggles
Two to
three ceramic tiles to set kiln on to cool and to set mold on during pouring
When you
are ready to use your kiln, here’s a few do’s and don’ts…
Do set up your workspace away from your home, in a well ventilated area.
Do keep your workspace free of flammable materials.
Do keep children and pets away from your work area.
Do always wear protective safety gear.
Do allow your kiln to warm up to a bright orange in the idle mode prior to
raising the temperature to suit your needs.
Do not crank the burner up and blast the kiln while warming the kiln up and do
not exceed 2200° F. When melting non-ferrous metals, you are just torturing the
kiln and vaporizing your metals, if you heat above 2200° F., anyway.
Do use quality crucibles in your kiln and always fill them to the proper
level, so they don’t boil over. Always inspect your crucibles prior to firing
and make sure none of them are cracked or heavily eroded from previous use.
Do not spill any borax flux onto the insulation of the kiln. Borax fluxes
silica. The insulation is 65 to 70% silica fibers. No need to explain what will
happen if you do.
Do always re-stack your kiln and leave the lid and burner in place until it
cools down, after using it and shutting down the burner.
Do not crank the torches up just to see what will happen.. If you want to know,
the insulation melts at approximately 3000° to 3200° F. and yes, I’ve done it.
Do use common sense, make sure you have adequate ventilation, be safe and
enjoy. There’s no room for error here, Guys and Gals.
Your Gold Processing Kilns Team |
