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Lockley

Member Since 05 Aug 2011
Offline Last Active Dec 17 2014 02:04 PM
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#67561 Raku Kiln- Highest Cone Temp

Posted by Lockley on 10 October 2014 - 11:54 AM

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




#60122 Noob Seeks Advice Building Kiln On The Cheap

Posted by Lockley on 06 June 2014 - 09:07 AM

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