[Clayart] dampers and flues

Hank Murrow hmurrow at efn.org
Tue Jul 25 09:54:00 EDT 2017


These are very good points from Robert;

When I first developed my Doorless Fiberkiln, I added up the development costs, production costs, and operating costs to arrive at a cost per firing, and published that figure in my advertising. My predictions have been largely been realized over the 32 years since I placed the first of twelve in service. The real performer in that group has been the kiln at the Shadbolt Centre for the Arts, in Burnaby, BC. that kiln is still firing with one repair for 2300 C/10 cycles, and pretty closely met my expectations for cost per firing.

Cheers, Hank in Eugene


> On Jul 24, 2017, at 3:05 PM, Robert Harris <robertgharris at gmail.com> wrote:
> 
> My biggest object to "My kiln fires for the cost of a mug", is that this
> does not adhere to most rules of accounting and economincs.
> 
> When calculating the cost of a kiln you need to include
> depreciation/amortization. In our guild we charge people not just for the
> natural gas, but also for the projected cost of replacing/rebuilding the
> kiln. For example our kiln has been rebuilt once, and needs to be replaced
> within the next five years. The bricks are 30+ years old, and simple can't
> be reused any longer.
> 
> I'd guess that the kiln has been fired 350+ times. But the current cost for
> a replacement is approaching $20,000. This doesn't include the cost of the
> rebuild about 15 years ago, nor periodic maintenance nor new kiln shelves
> or posts (even the most careful person breaks one every so often). Should
> we include cones in the cost, replacing thermocouples etc ... etc ... We
> estimate it costs well over a hundred dollars to fire a kiln (about the
> same size as yours) when you include replacement value. And to not include
> it, (particularly in the context of a guild/co-op setting) is at best
> disingenuous, if not dishonest (if you were a public company you would be
> breaking SEC regulations ;) ).
> 
> Robert
> 
> On Fri, Jul 14, 2017 at 5:39 AM, mel jacobson <melpots2 at visi.com> wrote:
> 
>> in my opinion, when building a kiln you have to be able
>> to change the size of your flue outlet, and try to think
>> of nils and the idea of turbulence at the flue.
>> 
>> even with higher altitude if the flue opening is too big, you just heat
>> the atmosphere. so, saying that...you should be able to take out a partial
>> brick, or add a partial brick until you get it firing just right.  i would
>> stay in the 40 square inch area to begin. just don't get in the 70-80
>> square inch size that so many old books talk about. it is just too big.
>> fuel is expensive...why waste it for nothing.
>> 
>> there is a reason our kilns fire so fast...like 5 hours.
>> the flue and stack are just perfect.
>> you can always fire longer, slow it down...but..when
>> you have to fire a 15 cube kiln for 18-24 hours...there is a problem..big
>> problem.  it is your money going up the stack.
>> learn to down fire..your life gets better.
>> 
>> bill schran, dave lyons and others were firing our small kiln to cone 11
>> in under 5 hours. 6 days in a row.
>> the kiln is in perfect balance. it is a one brick thick kiln. two stacks
>> of shelves. 11x16's. mn flat top.
>> kiln is made mostly of broken and rubble bricks. the needle on the gas
>> gage barely moves.  but, a great many people fight us like made...can't be
>> true...well, it is.
>> 
>> we like to tell people that the kiln is done before the outside of the
>> bricks get really hot.  it is true.
>> 
>> colleen and lynn fox, with john post built that kiln in two days. ben
>> burgert age 16 was the strong kid that did all the lifting. we used sacrete
>> to tie the block to the ground...level. it is rocky and sandy.  no slab
>> needed.
>> the next summer we built a wooden frame with a metal roof over the kiln.
>> nice little shelter.  cost was under a hundred bucks. (you buy that steel
>> roofing that is left over from other jobs...you know, in the corner of the
>> lumber yard...`hey joe, you want to get rid of that steel roofing?
>> 4/3 foot by 8 feet. who cares what color.
>> 
>> we fire about 45 pots or more, in five hours and the cost is
>> about 20 bucks for propane. do the math.
>> my 45 cubic foot natural gas kiln fires for the cost of a mug. true.
>> there is a reason i did not get a bigger meter.
>> that kiln fires in 9 hours, i do not rush it. that is the timing it has
>> always had. big kiln, lots of pots and shelves to heat up.  about 100 pots
>> a firing. (size matters when counting., of course.)
>> 
>> --
>> Mel's Website:  www.melpots.com
>> CLAYART PAGE:
>> 
>> http://www.melpots.com/CLAYART.HTML
>> 
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