GAS PROPANE CUPELLATION FURNACE

BASIC CUPELLING INSTRUCTIONS

1. Place the Kwik Kiln on a level fireproof surface. Align the torches with the side ports and gently insert the torch tips approximately ¼” into the side ports of the Kwik Kiln. Secure the torches with a suitable device so the torches don’t roll and the valves and tips are parallel with the surface.
2. Remove one of the torches and light it. Adjust the valve so that you have a clean blue flame approximately 1½” long. Re-insert the torch gently into the side port of the Kwik Kiln and replace the lid. Allow the Kwik Kiln to warm up for a few minutes, then slowly open the valve on the second torch until it lights. Once both torches are lit, remove the lid and adjust the valves on both torches until you have a clean blue flame protruding into the combustion chamber of the Kwik Kiln approximately ½” to ¾”, then replace the lid.Allow the kiln to warm up to a bright orange color. While the kiln is warming up, place the cupel on the lid so that the flame exiting the lid of the kiln comes into contact with the cupel. The flame exiting the kiln should be approximately 2” to 3” tall. Move the cupel around the lid until all sides of the cupel have been in contact with the flame, thereby preheating the cupel.
3. Remove the cupel from the lid and place the lead prill in the cupel. Remove the lid and place the cupel inside the combustion chamber, centering it inside of the Kwik Kiln. Replace the lid and continue to heat the cupel until the lead melts and the cupel opens. Continue to heat the cupel for a few minutes until the crust has moved off to the sides of the molten pool of lead and the pool of lead has stilled.
4. Remove the lid from the Kwik Kiln after the cupel has opened and has stilled. When the lid is removed, an oxidizing environment is created and the pool of lead begins to oxidize or ‘burn’ and is converted from metallic lead to litharge. During the conversion of metallic lead to litharge, an exothermic reaction takes place, significantly raising the temperature of the lead and cupel. However, when utilizing the Kwik Kiln, most of the heat from the exothermic reaction is released out of the top of the kiln and the contact of atmospheric oxygen also cools the pool of burning lead.Closely observe the burning pool of lead during the first initial stages of the process and, if there are any indications of the cupel beginning to freeze, replace the lid and let the cupel and pool of lead heat up for a minute or two, then, remove the lid and let the burning pool of lead convert to litharge once again.Once the temperature has stabilized and the burning pool of lead is being absorbed by the cupel, adjust the torches if necessary, so that the feathers and rings of litharge forming on the cupel are dark red to almost black. The color of the lead will be much brighter than the litharge being absorbed by the cupel, as the pool of lead is much hotter than the cupel or air surrounding it. The formation of abundant dendritic crystals of litharge (feathers) on the sides of the cupel is indicative of optimal cupelling temperatures of approximately 700 to 850 degrees Celsius.
5. During the end stages of the cupellation, as the alloy becomes richer, the bead becomes more and more rounded in shape and shining drops of litharge appear and move about on the surface of the bead. When the last of the lead goes off, these drops disappear and the fused litharge becomes very thin and gives an effect so that the bead appears to spin rapidly and presents a display of rainbow colors.Once you see this happening, replace the lid on the kiln and leave the lid in place until the bead ‘brightens’. Once the bead has brightened, continue to heat for a couple of minutes, while paying close attention to the feathers of litharge collected on the sides of the cupel. The temperature of the kiln should not be allowed to raise enough to melt the litharge feathers. If you see this occurring, immediately remove the lid and finish without the lid in place.After a couple of minutes, turn both valves on the torches off, leaving the lid in place and allow the cupel to cool slowly while watching for the ‘blick’ from the bead. As the bead cools and solidifies, it will emit a flash of light (blick) from the release of the latent heat of fusion. After the bead blicks or flashes and the cupel has cooled, remove it from the kiln and closely observe the surface of your bead. The color of the bead and the appearance of the bead’s surface may indicate the presence of certain metals contained within the bead.