actical
and experienced friends generally--one will sometimes hear the remark
that "they don't see that delay can do it much harm;" and when one asks,
"Can it do it any good?" the reply will be, "Well, probably it would be
as well to fire it soon;" or in the case of mixing, "To use it fresh."
Now, if it would be "as well"--which really means "on the safe
side"--then that seems a sufficient reason for any reasonable man.

But indeed I have always found it one of the chiefest difficulties with
pupils to get them to take the most reasonable precautions to _make
quite sure_ of _anything_. It is just the same with matters of
measurement, although upon these such vital issues depend. How weary one
gets of the phrase "it's not far out"--the obvious comment of a
reasonable man upon such a remark, of course, being that if it is out
_at all_ it's, at any rate, _too_ far out. A French assistant that I had
once used always to complain of my demanding (as he expressed it) such
"rigorous accuracy." But there are only two ways--to be accurate or
inaccurate; and if the former is possible, there is no excuse for the
latter.

But as to this question of freshness of colour, which is of such
paramount importance, I may quote the same authority I used before--that
of the _maker of the colour_--to back my own experience and previous
conviction on the point, which certainly is that fresh colour, used the
same day it is ground and fired the same day it is used, fires better
and fires away less than any other.

The facts of the case, scientifically, I am assured, are as follows. The
pigment contains a large amount of soft glass in a very fine state of
division, and the carbonic acid, which all air contains (especially that
of workshops), will immediately begin to enter into combination with the
alkalis of the glass, throw out the silica, and thus disintegrate what
was brought together in the first instance when the glass was made. The
result of this is that this intruder (the carbonic acid) has to be
driven out again by the heat of the kiln, and is quite likely to disturb
the pigment in every possible way in the process of its escape. I have
myself sometimes noticed, when some painted work has been laid aside
unusually long before firing, some white efflorescence or
crystallisation taking place and coming out as a white dust on the
painted surface.

Now it is not necessary to know here, in a scientific or chemical sense,
what has actually