266 
11£B^MIC STUDIO 
FIRING THE KILN 
See that all openings are closed, that the burner is 
clean. Put a small piece of asbestos fibre in burner to 
use as wick. Turn on oil slowly. As soon as the asbestos 
fibre is saturated with oil apply lighted match. It will 
ignite at once. I^et the oil flow drop by drop for about 
ID minutes so as to heat very gradually. Then let the oil 
flow in a very fine stream for twenty minutes more and 
you will soon have a steady flame and a strong roar if 
your chimney is right. This roar is music to the firer's 
ear. After the oil has flowed in a fine stream for 20 minutes 
you can gradually increase the flow until the bottom of 
the burner is nearly but not quite covered. Watch your 
chimney and if it smokes turn off some of the oil as you 
will not increase your heat, or hasten the firing, but clog 
your kiln chimney with soot. About the end of an hour 
a dull red light is visible, keep a steady fire and it gradually 
turns from red to orange. When the kiln is a dull red 
half way up glass would be fired, but it is very difficult to 
tell just the exact moment when glass is properly fired, 
only experience teaches that. If in firing china there is 
much lustre and colors with much oil, leave the httle sHde 
in door open until the first red heat, to allow the gases to 
escape. If a long piece extends from back to front hold 
the heat a little longer. A Revelation Kiln when properly 
fired is a luminous orange, a color comes just like sunshine, 
then a soft haze making the pieces almost lost to the sight. 
Only through knowledge of your kiln can you tell 
just the moment it is fired. A kiln has a- great deal 
of individuality and must be understood to make the most 
of its possibilities. A good deal depends on local conditions, 
drafts, etc. No one can tell you just how long to fire, how 
rapidly to push the heat, you must learn for yourself. By 
following general directions this is easily learned. Fire 
slowly, you can scarcely fire too slowly if the pieces are 
large. In most cases fire hard. Amateurs as a rule under- 
fire more than they overfire. Above all allow the kiln 
to cool slowly. Breakage occurs in cooling, in passing too 
rapidly from red to black. If there is a damper in the 
pipe turn it on after the fire is out to prevent too rapid 
cooling. An ordinary Revelation kiln consumes about 
i^ gallons of oil and takes from i^ to two hours to 
fire, but it depends on conditions, sometimes it takes 
longer, but rarely less than one and one-half hours. Prof. 
Edw. Orton of the University of Ohio, Columbus, makes 
Pyrometrie cones for over glaze firing, these different 
cones melting at a different temperature. Place cones at 
back and front of kiln and experiment until you know 
just how much heat will melt each cone. In house kilns 
the average heat for firing china is 2,000 degrees Fahrenheit, 
sometimes a little more or less, not so high for glass. 
It is well to speak a little on the effect on colors of an 
over or an under fire. 
Pompadour if fired too hard is gray in tone, under- 
fired it rubs off. The only way to get a good glaze is to 
fire hard, if glaze is not good fire harder, but not the car- 
mines or pinks, they should be put on for last and light fire. 
If the ware has a high glaze before painting it does 
not signify that it needs a hard fire, for instance Belleek. 
Raised enamels should be fired only once, else they wiU 
chip off and remove glaze with them. Flat enamels over 
tint take a lighter fire than over white china, over grounded 
color lighter still. Pinks if underfired are yellowish. 
Ruby underfired is brownish, put on too thick will scale, 
Gold underfired will turn dark and rub off. It will fire 
right at a lower temperature than Ruby Purple. Colors 
if underfired lack glaze and look dirty and will collect dirt. 
Colors such as Ruby Purple, Red Brown, laid on heavy 
and underfired will scale. Iron Reds, Carnation, Pompa- 
dour, Blood Red and Deep Red Brown generally fire all 
right in delicate shades, but sometimes fire out completely, 
or rub off. If the latter, go over with a gold color as car- 
mine. 
Aufsetzweis and paste stand many fires but if later 
fires are lighter than the first, are apt to chip. Too many 
fires are not good for any wares especially Belleek. Three 
or four are about all that are safe for French, but the re- 
sult might be good if more are necessary. Large pieces 
can have smaller pieces placed in them to be fired, using 
stilts to separate them, do not try this in Belleek. Never 
crowd the kiln, it is best to have it well filled but not crowded. 
Do not fire large trays flat. Carmines are test colors, if 
underfired, yehowish red, overfired, purphsh. They will chip 
and turn yellow if put on too heavy. 
Grays loose their strength in firing. Yellows fire stronger. 
Black fires with a high glaze, Greens change very 
little in firing, glaze easily, regular heat. 
Color that is to have gold worked over it should have 
a strong fire 
Enamels all fire a stronger color than appear on the 
palette except the Reds. 
