Let no one suppose, however, that the artist is hampered by these limitations on the higher side of his work. On the contrary, they set him free to tell his story his own way. Ruskin—poor Ruskin, out of date, ridiculed, forgotten—pointed out long ago, in writing of Giotto's frescoes, the advantage which the pure colourist has over the chiaroscurist in his power of telling a story. In our times the fact has been rediscovered with a flourish of trumpets by the Post-Impressionists. I have no great enthusiasm, I confess, for the way in which they have carried out their principles, but I do know two perfect tellings of the story of the Creation. One is in mosaic on the ceiling of the narthex of St. Mark's at Venice, and the other is in the upper part of the east window of York Minster; and in each case the language used consists of flat forms and colour only.
II
THE BEGINNINGS OF STAINED GLASS
II
THE BEGINNINGS OF STAINED GLASS
I have said that stained-glass work is the product of the union of two crafts, the glazier's and the enameller's. The glazier's work being the groundwork of a window, I will take it first.
Glass-making.
What, to begin with, is glass? It is sand melted and run together. The best sand for the purpose is that which is most largely composed of the substance called silica, such as sand formed of powdered quartz, or flint. For some reason, the silica when melted does not recrystallize on cooling as might have been expected, but forms an even transparent substance, plastic while still hot. Think of the tremendous effect this one natural fact has had on the architecture, dress, and, probably, the physique of the nations of northern Europe.
Given sufficient heat, glass can be made by this means alone, but the heat required is so great that it has only been done in recent years for special purposes by means of the electric furnace. Failing this, the sand must be induced to melt at a lower temperature by means of a flux, for which either potash or soda may be used, and to which lime or lead must be added, to enable the glass to resist moisture. (Theophilus, describing the process in his Treatise, certainly no later than the thirteenth century, recommends the use of beech twigs calcined in an earthen pot, whence the name "Pot-ash.")
Colouring.
Glass may be coloured or "stained" while in a molten condition by the admixture of various substances, mostly metals, gold, copper, manganese, and so on, the result depending on the temperature to which it is subjected and on the exact composition of the glass as well as on the colouring matter used.