A word about kilns.
Jul 18, 2015 13:27:33 GMT -6
Post by tileman2 on Jul 18, 2015 13:27:33 GMT -6
From my own personal observations and experiences. Every clay thrower on this forum will have personal likes and dislikes about kilns. Regardless of the brand you choose, there are some basic requirements for kilns used for crystal firings. First, heed Avi's advice given in this thread section: nothing like the voice of experience to keep you from making costly mistakes. So here is a short list I would give consideration for those venturing into the crystal ocean for the first time.
The majority of kilns are built for use by various arts, and some are built for studio potters, and just a handful for us chronically obsessed crystal junkies. Two primary areas that need to be on the top of the list is insulation value: which is a combination of brick type, brick thickness, and additional fiber board. The other is power which is rated in wattage; amperage is shown only as a guide to indicate total electrical load at peak demand. Overlooking these two crucial points will alter the outcome, and cost you money in the long run. Kilns are like people after that; each one has its own personality. By which I mean hot and cold spots, strengths and weaknesses; ability and lack. A top loader will have hot and cold spots, sweet spots, and sour spots in some places: and a front loader in others. There is no such thing as a perfect kiln; there is however the operator who learns how to control the kiln of choice.
K-23 and K-26 are the two most widely used bricks in the vast majority of kilns. K-23 will hold heat in the chamber, however K-26 actually provides insulation value. The common thickness is 2.5 or 3.0 inches: there are however models with custom 4.5" thick IFB (insulated fire brick) brick for production models. Crystals require more than the normal heat, and they are required to hold heat for extended periods during the firing cycle. So consequently it is only logical that the kiln has either thicker, higher value IFB brick like K-26, or a lower value K-23 brick with additional fiber board. A true high fire kiln will have a minimum of 3" brick thickness; and preferably added fiber board. The more heat the kiln can hold, the higher it can fire, and the less it has to work to achieve that goal. A poorly designed kiln, or a kiln not built for high firing schedules will struggle to reach and maintain temperature which equals poor crystal development. Most kiln companies have recognized the growing demand for high fire kilns and have introduced models specifically for that purpose.
Power consumption is as important as chamber design. Most any kiln can fire from room temp up to 2000F with very little problems. In fact, in today's market hitting 2200F is not that big of an issue. From 2200F and up is where the struggle begins; and that is also the most crucial firing range for crystals. Cone 6 crystal firings are popular, some use cone 8 and some fire up to cone 10 and nudge cone 11. Very few kilns are built that can handle these demands day in and day out. L&L kilns has the Quad Pro series for crystals: so I will use their specs as a reference. The 6.7 CF model has 13,400 watts of available power: so the standard is by simple math: 13,400 divided by 6.7CF = 2006 watts per CF of kiln space. Bear in mind that this is a production model designed for the rigors of almost daily use. You have to decide and project current and future use of your kiln. I have a 1.75 CF Paragon that I use primarily for testing. 6400 watts divided by 1.75 CF = 3657 watts per CF. Skutt has a high fire model that is 6.6CF with 11,520 watts = 1745 watts per CF.
So when kiln shopping, look at the chamber design in regards to brick type, brick thickness, and additional fiber board insulating properties. Then do the simple math in terms of available power: personally I would not consider anything below 1700 watts per CF for daily use. In regards to test kilns, as noted above the one I use has almost twice the power of larger production kilns. If you are considering a test kiln; try to select one that duplicates the design of your production kiln so results are somewhat equal in outcome. If you are considering a front loader; elements in the door are a must have. Those who own front loaders are well aware that after only a couple of uses: the door distorts just enough to draw in small amounts of room air. I also own a Super Dragon and a 6.5CF custom built top loader.
Other considerations: Type S thermocouple> must have.
Electronic programmer> must have. Must have the ability to program your own firing schedules.
Stainless Steel Skin: not mandatory, but it is much easier to care for.
Kiln Vent: not mandatory, but are very useful in evening out heat, venting gases.
APM elements: not mandatory but Kathanal A-1 is at a minimum. Would advise APM's however.
Interface programs are useful, but not mandatory.
Buy a kiln that you know an area dealer can service if you do not know how.
Give your local dealer your specifications for a kiln, not vice versa.
The hardest issue to deal with is projecting use. If you are a hobbyist, then the choices are much easier. If you plan on becoming a studio potter making your living: then you have to consider future use and growth. If you have never indulged in crystals before; you might be money ahead buying a good test kiln to get your feet wet before big investments. The end result of all of this advice is simple: whatever kiln you buy, you will learn to compensate and fire for crystals. However, these four areas must be met: chamber design/ insulation value, available power, Type S thermocouple, programmable controller. Skimp on any of these four and all you will grow is impatience.
Tom - Happy Crystals- follow Avi's advice above.
Keeping your results similar between your test kiln and your production kiln: recommended by Koz: tested- it works.
The majority of kilns are built for use by various arts, and some are built for studio potters, and just a handful for us chronically obsessed crystal junkies. Two primary areas that need to be on the top of the list is insulation value: which is a combination of brick type, brick thickness, and additional fiber board. The other is power which is rated in wattage; amperage is shown only as a guide to indicate total electrical load at peak demand. Overlooking these two crucial points will alter the outcome, and cost you money in the long run. Kilns are like people after that; each one has its own personality. By which I mean hot and cold spots, strengths and weaknesses; ability and lack. A top loader will have hot and cold spots, sweet spots, and sour spots in some places: and a front loader in others. There is no such thing as a perfect kiln; there is however the operator who learns how to control the kiln of choice.
K-23 and K-26 are the two most widely used bricks in the vast majority of kilns. K-23 will hold heat in the chamber, however K-26 actually provides insulation value. The common thickness is 2.5 or 3.0 inches: there are however models with custom 4.5" thick IFB (insulated fire brick) brick for production models. Crystals require more than the normal heat, and they are required to hold heat for extended periods during the firing cycle. So consequently it is only logical that the kiln has either thicker, higher value IFB brick like K-26, or a lower value K-23 brick with additional fiber board. A true high fire kiln will have a minimum of 3" brick thickness; and preferably added fiber board. The more heat the kiln can hold, the higher it can fire, and the less it has to work to achieve that goal. A poorly designed kiln, or a kiln not built for high firing schedules will struggle to reach and maintain temperature which equals poor crystal development. Most kiln companies have recognized the growing demand for high fire kilns and have introduced models specifically for that purpose.
Power consumption is as important as chamber design. Most any kiln can fire from room temp up to 2000F with very little problems. In fact, in today's market hitting 2200F is not that big of an issue. From 2200F and up is where the struggle begins; and that is also the most crucial firing range for crystals. Cone 6 crystal firings are popular, some use cone 8 and some fire up to cone 10 and nudge cone 11. Very few kilns are built that can handle these demands day in and day out. L&L kilns has the Quad Pro series for crystals: so I will use their specs as a reference. The 6.7 CF model has 13,400 watts of available power: so the standard is by simple math: 13,400 divided by 6.7CF = 2006 watts per CF of kiln space. Bear in mind that this is a production model designed for the rigors of almost daily use. You have to decide and project current and future use of your kiln. I have a 1.75 CF Paragon that I use primarily for testing. 6400 watts divided by 1.75 CF = 3657 watts per CF. Skutt has a high fire model that is 6.6CF with 11,520 watts = 1745 watts per CF.
So when kiln shopping, look at the chamber design in regards to brick type, brick thickness, and additional fiber board insulating properties. Then do the simple math in terms of available power: personally I would not consider anything below 1700 watts per CF for daily use. In regards to test kilns, as noted above the one I use has almost twice the power of larger production kilns. If you are considering a test kiln; try to select one that duplicates the design of your production kiln so results are somewhat equal in outcome. If you are considering a front loader; elements in the door are a must have. Those who own front loaders are well aware that after only a couple of uses: the door distorts just enough to draw in small amounts of room air. I also own a Super Dragon and a 6.5CF custom built top loader.
Other considerations: Type S thermocouple> must have.
Electronic programmer> must have. Must have the ability to program your own firing schedules.
Stainless Steel Skin: not mandatory, but it is much easier to care for.
Kiln Vent: not mandatory, but are very useful in evening out heat, venting gases.
APM elements: not mandatory but Kathanal A-1 is at a minimum. Would advise APM's however.
Interface programs are useful, but not mandatory.
Buy a kiln that you know an area dealer can service if you do not know how.
Give your local dealer your specifications for a kiln, not vice versa.
The hardest issue to deal with is projecting use. If you are a hobbyist, then the choices are much easier. If you plan on becoming a studio potter making your living: then you have to consider future use and growth. If you have never indulged in crystals before; you might be money ahead buying a good test kiln to get your feet wet before big investments. The end result of all of this advice is simple: whatever kiln you buy, you will learn to compensate and fire for crystals. However, these four areas must be met: chamber design/ insulation value, available power, Type S thermocouple, programmable controller. Skimp on any of these four and all you will grow is impatience.
Tom - Happy Crystals- follow Avi's advice above.
Keeping your results similar between your test kiln and your production kiln: recommended by Koz: tested- it works.
Koz said: If you want more control, just program in a cooling rate from your top temperature.
I fire just into cone 11, then from that top temperature program in a 300 degree per hour cooling rate to my first hold.
I get the same results from my small kiln to my larger kiln that way.
I fire just into cone 11, then from that top temperature program in a 300 degree per hour cooling rate to my first hold.
I get the same results from my small kiln to my larger kiln that way.
