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  1. Pieter, I really think if you go to your welding supplier you will find that the glass inserts used in welding helmets are very inexpensive. Most welding suppliers also have a selection of dark polycarbonate "sun glass" style safety glasses that welders and people that work near them use when not directly performing welding operations. I say this as long time member of ABANA (Artist-Blacksmith's Association of North America) One of the key safety issues for long term Forge/Kiln/Glass workers is the exposure to, not only ultraviolet radiation. but also long wave infrared radiation. The damage that the eyes receive from high temperature exposure is cumulative. I hope you have a lovely holiday and a safe New Year. Lockley
  2. One thing that hasn't really been separated out in this discussion is the difference between pyro cone and temperature. It is comparatively simple to reach a temperature in the yellow white range in a propane furnace. That is mostly a function of BTU in and volume. Cone is a function time at temperature or heat work. I know that most readers of this forum make that assumption know this but for the casual or newer member it would be well to be more explicit. When people say that running cone 6 in a Raku kiln would me unreasonably expensive in terms of fuel I take that as recognizably true. If one assumes a Small Orton cone this gives a temperature of 1255C with a temperature rise rate of 300 C/hr. Cone 04 on the other hand seems more achievable as a small Orton cone is 1098C @ 300 C/hr. Personal experience tells me that the time an effort to go from and orangish yellow to yellow white heat is a lot. All this is in aid off is the point that Raku is more Art and Craft and Experience than many other parts of custom made ceramics. Lockley
  3. The technique of heat recovery from exhaust gases has a long history. In the days of open hearth steel making they created alternating exhaust paths called "Checkers". The checkers were stacks of pyro brick that heated up on the exhaust cycle and preheated the air on the intake cycle. Counter current heat exchange is used and any number of industrial processes to improve heating cycles. It is also used in the feet of migrating water fowl to keep from freezing in ice filled ponds. In my own experience I have used Black Iron pipe ( not galvanized pipe) with propane in a blower system to increase the temperature I achieve. Black iron is relatively inexpensive compared to stainless steel, and because it is thread-able by most suppliers it can be assembled in manifolds without welding. This makes replacement of parts a days work not a weeks. I used straight pipes not coiled, and of a large diameter to slow the flow down with out reducing volume. I didn't worry about the iron pipes because it is kind of like the "Mr. Wizard" trick of boiling water in a paper cup over an open flame. As long as air flowed through the pipe was ok despite the temperature would have melted steel. For a wood fired system I have been toying with designs using two different sizes of fire place flue tiles. One outer and one inner.
  4. Have you considered the option of two supply cylinders with two regulators supplying one line with a control valve leading to your burner? Set the regulators to a slightly higher pressure than needed and use the valve to throttle delivery down to your requirements. Just a thought Lockley
  5. A couple of thoughts on your project. one) Small propane furnaces / kilns are the least efficient way to fire any thing. For the temperature achieved the total BTU expense is inversely proportional to the volume heated per item. As a means of experimenting with the local clay I rather doubt you will find it satisfactory. Since you are a rural area you might find it better to experiment with wood/agricultural waste fired kilns. I would not dismiss the local potters so casually. In my experience with various crafts local knowledge will often trump academic knowledge. Making friends with local potters may teach you things about local conditions and materials that will speed you toward satisfactory results. In addition my experience with small propane fired furnaces/kilns/forges, has shown that control problems increase as size decreases. two) Commercial burners from companies like WARD Burners are by far the most practical way to build a kiln. Failing that there is a resource for building burners that I have not seen listed here before. Gas Burners for Forges, Furnaces & Kilns by Michael Porter copy right 2004 Published by SkipJack Press, Ocean Pines, MD Library of Congress # 2003115257 The contents of this book will short cut a lot of errors and futile effort, I wish it had been available 30 years ago. It is possible to build a Kiln burner with very simple plumbing fixtures but making one with the necessary range of turn down (variation of BTU output ) is difficult and very difficult with out first class gas regulators. You may want to read the extensive discussion of Kiln firing that appeared on this forum last week. Good Luck Lockley
  6. Wow, John Baymore has provided a world of detailed information and analysis of this problem. Wish, I could make it to New Hampshire and sit at his feet. I'd like to and something about regulators. If you have not already, go to your local industrial gas, welding gas suppler, and purchase a high volume propane regulator. They are relatively expensive but provide the capacity and volume needed in this application. Propane fuel is used in an number of industrial application so they are usually available quickly on order. There are, in most manufacturer catalogues, three size of each regulator bodies. You want the largest. I like the suggestion of ganging together several 100# tanks. However, If you decide to do that consult your supplier of welding supplies and purchase the equipment they supply to industry for assembling a Propane Supply manifold. You may not realize it but, even though you may see your self as a craftsman artist, when you shift to firing in an independent kiln your feet are on the first rung of the industrial ladder. Many aspects of Ceramics are best done by creative and envelop stretching artists but running a kiln is a serious business and no place for cheaping out. Lockley
  7. I think your problems with this kiln would indeed be solved with a power burner. Naturally aspirated systems are a little tricky to operate in my experience. In my checkered career I've built a large number of naturally aspirated systems. I've found low pressure systems to be the most difficult to make work. Naturally aspirated burners are incredibly sensitive to down stream and up stream resistance . Too much resistance in front of the burner and it will back burn. To much resistance behind the burner it burn orange and smoky. There is another problem, which is referred to as resistance to mass transfer, meaning that hot gases are harder to move in volume because the individual molecules are moving so fast in a chaotic pattern. The burn problem you show in your video tells me that the total velocity of your air fuel mixture is to slow for the diameter of the burner. How to solve it? Either reduce the resistance in front of it or increase the gas velocity entraining air by increasing pressure. Given your previous discussion I vote for moving your splash bricks toward the center and moving your whole bag wall back an inch or so. Lockley
  8. The usual material for a mortar and pestle is some grade of Porcelain. Coors and Co. comes to mind as the leading maker of commercial wear of that type. Many of the Mexican mortars are made of volcanic rock. I can't make a specific recommendation for clay. I don't know enough.
  9. IFB does benefit from a skim coat of refectory coating. The high carbon monoxide content of fuel gas firing tends to age IFB prematurely. There are a number of coating which will also improve the efficiency of your Kiln. Any area with direct flame contact should be lined with standard fire brick or minimally coated with refectory cement. The suggestion of surrounding the kiln with insulating blanket is excellent. There is a hardener which will firm the outer layer of ISB and make it more stable. In the past I have built shelters around my units from salvaged galvanized duct work and never found the metal dangerously hot when protecting layers of ISB/IFB.
  10. The basic concept created in the article is highly similar to that used in the foundry and steel production industries. Recovering wasted heat from exhaust gas is in fact the only practical way to produce steel. A number of Artisan iron and bronze workers use heat recovery systems for their small furnaces. I have been scheming to create a lower fire system for my own use. The use of and extruder to fabricate refectory tubes is something that had simply never occurred to me. I applaud the creators and developers the recuperative Pottery Kiln for their ingenuity in adapting the concept to the unique demands of Pottery.
  11. For the most helpful information on burner systems for Kiln's You will want to contact: www.wardburner.com They are very helpful and able to supply safe systems for any size kiln with integrated control. Dimmer switches need not apply! Lockley
  12. Just a quick comment about the Brick. A number of years ago I had a long discussion with an engineer for A.P. Green company( a company that has since been rolled into a conglomerate) the manufacturer of Empire Brick. Yes the DP brick is excellent for hot face applications. In the course of analyzing my proposed design it turned out that at typical Kiln temperatures hard brick is essentially transparent to heat imput. (Heat leaves as fast as it arrives) This means your eventual kiln will need insulation to the same extent as an entirely soft brick Kiln. There are a number of coatings for face brick which will slow or reduce the rate of heat transfer. They are made with zirconium compounds if my memory serves. Lockley
  13. I forgot part of my intent in my reply. The online wheels and plans noted above on google are much better than those I bought on ebay a couple of years ago. The tapered wheels bearing will carry both the thrust and side loads required. I plan to avoid the complicated machine style attach ment of the bearings to pipe by simple and careful application of highgrade epoxy to carefully prepared surfaces. You might suppose that this is a questionable use of metal filled epoxy. A number of years ago I had wheel spline strip on a Rambler I was driving, Not being able to find a replacement I cleaned and epoxied the real wheel flange back to the rear axle and drove another 50000 miles on it before disposal of the entire vehicle. Lockley,
  14. I'm a little confused about your problem. The most easily available bearings that will do the job are the trailer wheel bearings available at many places where outdoor equipment or boats are sold. The bearings are relatively inexpensive. The bearings are tapered roller bearings designed to carry weight in what ever direction they are placed. { } rt left for instance. There are many possible designs. For me the bigger problem is getting a balanced mass for the inertia wheel which stores your energy between strokes. A wheel can be relatively portable but the inertia wheel, which is common to both kick and tredle potters wheels, usually is the hardest thing to trans port. I have settled on making a wooden form and then I'm going to pour sector of 8 sectors of about 12.5 lbs each which will give a 100 lb mass. Many of the online plans specify items which are not readily available. The plans I have specify building the frame out of oak. I would love to but the cost of oak today makes the cost of a new kick wheel almost attractive. Good Luck, Lockley
  15. Homemade conversions are subject to all sorts of problems. The folks at ward burners are very helpful if you ask them. One of the possible causes of your problems may be, strangely. too much resistance from your kiln. Back pressure created by the Kiln contents reduces an atmospheric burners ability to induce air flow into the kiln. The exit of a kiln should be capable exausting at least the volume of the gas and air going in. As a kiln heats atmospheric burners often need their mixtures adjusted to maintain the desired chemistry. A hot kiln creates more back pressure than a cold one. Lockley ps. adding oxygen will solve nothing and entail enormous expense. Kiln conversions are created not designed. My experice with the people at Ward's is that they will help you redesign your conversion. they need to know the volume, the inlet sizes, the burners you have , the orifice sizes, and the vent system and its dimensions, as well as the kind of supply system you are using including the specifications of your regulators.
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