And can you not get it?
Well, yes! but you want experience and constant watchfulness—in short, "rule of
thumb." For every different glass differs in hardness, and you never know, except by memory and constant handling of the stuff, exactly what your materials are going to do in the kiln; for as to standardising, so as to get the glass into any known relation with the pigment in the matter of fusing, the thing has never, as far as I know, been attempted. It probably could not be done with regard to all, or even many, glasses—nor need it; though perhaps it might be well if a nearer approach to it could be achieved with regard to the manufacture of the lighter tinted glasses, the "whites" especially, on which the heads and hands are painted, and where consequently it is of such vital importance that the painting should have careful justice done to it, and not lose in the firing through uncertainty with regard to conditions.
Nevertheless, if you observe the rule to fire sufficiently, the worst that can happen is a disappointment to yourself from the painting having to an unnecessary extent "fired away" in the kiln. You must be patient, and give it a second painting; and as to the "rule of thumb," it is surprising how one gets to know, by constant handling the stuff, how the various glasses are going
to behave in the fire. It was the method of the Middle Ages which we are so apt to praise, and there is much to be said for practical, craftsmanly experience, especially in the arts, as against a system of formulas based on scientific knowledge. It would be a pity indeed to get rid of the accidental and all the delight which it brings, and we must take it with its good and bad.
The second rule with regard to the question of firing is to take care that the work is not "stale" when it goes into the kiln. Every one will tell you a different tale about many points connected with glass, just as doctors disagree in every affair of life. In talking over this matter of keeping the colour fresh—even talking it over with one's practical 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