I.Lewis on sun 5 dec 99
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The Promise. Firing times
? How many people keep a log of time v temperature when they fire their =
kilns?
A useful exercise is to put in a delay into the programme, be it manual or
electronic control and record temperature increase at fifteen minute =
intervals.
If you use a control system or programme which increases gas flow every =
sixty
mins, change this to ninety minute intervals. Keep a plot of the rate of
temperature increase and the times at which cones slump. At the same time
monitor the burners and note the condition of the flames. Ensure that they =
are
not smoky but burning completely with a minimum amount of draught by =
adjusting
shutter valves and dampers. Comparison of the plots for the faster firing
against the slower firing will enable judgements to be made about =
efficiency.
One thing I have promised myself is to weight the gas bottles before and =
after a
firing but I have never done it. With nearly three hundred and fifty firings=
on
the log of the kiln I am currently using I could just about set a clock on =
the
cones because the time interval from lighting up to setting is so =
consistent.
But I did keep plots over the first few firings and adjusted the rate of =
heat
input to give a uniform slope on the graph.
Current industrial practice is to reduce all manufacturing times to a =
minimum,
getting down towards two hours, bag to pack and despatch. But all raw =
materials
are selected and prepared with this in mind and automated firing programmes
incorporate dwell times to overcome those nasty quartz inversions..
Ivor Lewis.
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