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.
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