Paul Borian on fri 23 jun 06
The other day my kiln was holding at cone 11 (top temp) so long that it
seemed stuck there, i was trying to bring the temp down to the cone 9 range
and then soak. These gravity-fed waste-oil burners have a number of ways to
control them but it is not as simple as adjusting a ball valve like with
gas burners. What i really wanted to do was open the damper fully in hopes
that considerable amounts of heat would be lost up the chimney but i was
reluctant to open it too much because it would draw more heat toward the
bottom, which is the hottest part for me and i am always trying to get as
much heat as possible toward the top by keeping the damper in, and also i
was concerned it would actually cause the temp in the kiln to rise since it
would allow for a more oxidizing atmosphere (it was still in light
reduction). So i didn't mess with the damper too much but was wondering if
this technique could actually work and, if so, anyone uses it?
I have found that holding for a relatively short period of time at top
temp, then dropping the temp slightly and holding for a long time to be a
very good firing schedule for the glazes i use, elminating most surface
defects and evening out temp in the kiln. It is this initial drop of temp
that can be difficult to achieve, at least with this burner system.
thanks,
Paul
Paul Herman on fri 23 jun 06
Hi Paul,
If you open the damper (oxidize), it seems like the temperature would
go UP instead of down, if the fuel setting remains the same.
What is it about the burners? Is there some reason you can't simply
decrease the flow of oil a little bit?
Best,
Paul Herman
Great Basin Pottery
Doyle, California US
http://greatbasinpottery.com
On Jun 22, 2006, at 11:23 PM, Paul Borian wrote:
> The other day my kiln was holding at cone 11 (top temp) so long
> that it
> seemed stuck there, i was trying to bring the temp down to the cone
> 9 range
> and then soak. These gravity-fed waste-oil burners have a number of
> ways to
> control them but it is not as simple as adjusting a ball valve like
> with
> gas burners. What i really wanted to do was open the damper fully
> in hopes
> that considerable amounts of heat would be lost up the chimney but
> i was
> reluctant to open it too much because it would draw more heat
> toward the
> bottom, which is the hottest part for me and i am always trying to
> get as
> much heat as possible toward the top by keeping the damper in, and
> also i
> was concerned it would actually cause the temp in the kiln to rise
> since it
> would allow for a more oxidizing atmosphere (it was still in light
> reduction). So i didn't mess with the damper too much but was
> wondering if
> this technique could actually work and, if so, anyone uses it?
> I have found that holding for a relatively short period of time at top
> temp, then dropping the temp slightly and holding for a long time
> to be a
> very good firing schedule for the glazes i use, elminating most
> surface
> defects and evening out temp in the kiln. It is this initial drop
> of temp
> that can be difficult to achieve, at least with this burner system.
> thanks,
> Paul
>
Ivor and Olive Lewis on sat 24 jun 06
Dear Paul Borian,=20
In your description of your process you do not say if you are =
curtailing or restricting you fuel flow into your kiln.
The second question is, how do you know your kiln was stalling at cone =
11?. Do you have a pyrometer that indicates temperature is declining or =
stationary? Without this you would not know if the interior temperature =
of your kiln had declined. Getting a good balance between declining =
temperature and even heat distribution is going to be a test of =
ingenuity and good record keeping, including local atmospheric =
conditions.
It seems to me that you need to reduce fuel flow and open your damper =
sufficient to get a slightly increase in air velocity. Do not be in =
haste to crash cool. This may freeze the surface of the glaze on the =
sides of your work facing incoming cold air. It may also affect colours =
of your glazes.
Keep on trying, you will get results eventually.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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