t who is to describe in writing this process in
all its forms? For there is, perhaps, nothing in the art of
stained-glass on which there is greater diversity of opinion and
diversity of practice than this matter of firing. But let us make a
beginning by saying that there are, it may be said, three chief
modifications of the process.

First, the use of the old, closed, coke or turf kiln.

Second, of the closed gas-kiln.

And third, of the open gas-kiln.

The first consists of a chamber of brick or terra-cotta, in which the
glass is placed on a bed of powdered whitening, on iron plates, one
above another like shelves, and the whole enclosed in a chamber where
the heat is raised by a fire of coke or peat.

This, be it understood, is a slow method. The heat increases gradually,
and applies to the glass what the kiln-man calls a "good, soaking heat."
The meaning of this expression, of course, is that the gradual heat
gives time for the glass and the pigment to fuse together in a natural
way, more likely to be good and permanent in its results than a process
which takes a twentieth part of the time and which therefore (it is
assumed) must wrench the materials more harshly from their nature and
state.

There are, it must be admitted, one or two things to be said for this
view which require answering.

First, that this form of kiln has the virtue of being old; for in such a
thing as this, beyond all manner of doubt, was fired all the splendid
stained-glass of the Middle Ages.

Second, that by its use one is entirely preserved from the dangers
attached to the _misuse_ of the gas-kiln.

But the answers to these two things are--

First, that the method employed in the Middle Ages did not invariably
ensure permanence. Any one who has studied stained-glass must be
familiar with cases in which ancient work has faded or perished.

The second claim is answered by the fact, I think beyond dispute, that
all objections to the use of the gas-kiln would be removed if it were
used properly; it is not the use of it as a process which is in itself
dangerous, but merely the misuse of it. People must be content with what
is reasonable in the matter; and, knowing that the gas-kiln is spoken of
as the "quick-firing" kiln, they must not insist on trying to fire _too_
quick.

Now I have the highest authority (that of the makers of both kiln and
pigment) to support my own conviction, founded on my own experience, in
what I am here goi