Coloured glass always attracts even the untrained eye: it is easy to understand why its bright colour and transparency should catch the eye of even a child. No other craftsman deals in such a tactile and beautiful art form: even before the brush touches it, it is a regal thing, The modern glass-blower works with an eye upon the product of the Middle Ages, his streaked reamy and seedy sheets that are full of bubbles, thick and sombre, or thin and brilliantly translucent, such as were made in Normandy and Lorraine in Eastern France in the Fifteenth Century.

The smooth thin glass that spoilt their windows around 150 years ago no longer hampers glass-painters. As a means of decoration coloured glass stands alone, in that it transmits light: it does not merely reflects it as a picture must d. Even the most lustrous, radiant gems can only reflect light from one facet through another, but stained glass directly transmits and enriches the sunlight itself. This translucency has the quality of “pulling together” colours, otherwise discordant, into pleasing contrast or unexpected harmonies. It invites daring combinations, or permits domination by one tone of colour that would be fatal in any opaque material.

The lightness of the artist’s hand helps. The essential quality of glass being translucency, the more it is painted the less it fulfils its purpose. He who paints his glass the least is master of glass painting. Compare fifteenth century glass with the best of those heavily shaded windows in vogue 150 years ago, and it is at once clear why pre-Reformation glass glows like fire when placed beside Victorian work.

The early painter laid his shadows lightly where required, stippling them with the point of a brush to mere films of shade-work, the tiny holes made in the pigment by each hair of the stipple brush still further helping the transparent effect. Shadows apart, the glass was clear. But the modern painter lays his shading pigment in one thick level coat over the whole surface of the glass, picking out his highlights with a stiff brush or a wooden pick after the paint is dry.

While making for strong contrasts of light and shade, this tends to darken the window, and by impairing the transparency of the glass also deadens its colour values; but it is a quick and easy way of working, and most of our modern glass painters have been trained in it. Its greatest merit in their eyes is probably that it leaves a zone of shadow around each pane, thus lessening the abruptness of the lead lines. The public, unable to appreciate the technical necessity or aesthetic value of these densely black lines, have tried for 600 years to dissuade the glass painter from their use, and the measure of decadence in stained glass has been exactly the measure of their success.

It is not due to lack of interest in his craft that the glass painter need complain. His troubles are rather due to ignorance of what constitutes good work. People are sufficiently interested in stained glass, but few understand its merits or demerits. The general public still demand, as they probably demanded in the twelfth century, that stained glass windows shall be transparent pictures. When a glass painter obeys that demand and spoils his window, the “cry” is raised that the secrets of old stained glass are all but forgotten. There never were any secrets, and if the medieval glass painters had possessed the technical skill of their modern brethren, it is probable that pictorial decadence would have set in about the year 1200 instead of 300 years later.

But unfortunately their methods and materials were clumsy, and the nearest thing they could do to pictures were those gorgeous screens of jewels, songs in colour, which nowadays we make pilgrimage to Chartres or Canterbury to see.

Glass painted in England today as good as any ever done; we are of course fortunate to have modern studios with modern equipment such as infrared kilns, and digital readout pyrometers. Even so we probably have as many as 40 or so artists in these islands who really understand their craft and are in tune with this unusual medium, and who can and do produce honest work.

And there are perhaps half a dozen or so masters of the craft doing work today on the level with that of Jean Coussin or Engrand le Prince. They are comparatively unknown, of course, for their works are their only advertisement which all can read.