Stained Glass

Who put the stain in stained glass?  This question feels a little like asking who put the ram in the ramalamadingdong?  We don’t actually know who came up with the technique of staining glass.  It is an ancient technique used as far back as the time of the early Egyptian Pharoahs.  Doubtless, the secret was lost and rediscovered several times.  Roman stained glass has been found and, of course, it became popular in the Gothic period for churches in Europe.    

Color versus Stain

Colored glass is not stained glass.  The colored glass used in stained glass windows involves adding different minerals in small amounts to the glass ingredients in a pot and are part of the liquid mixture.  These minerals contain metal ions that give the glass color—a topic for another article.  These pieces of colored glass are colored throughout the piece. Stained glass, however, has color that is incorporated into the surface of the glass.

Silver is the Secret

The “stained” glass came about from a clever process involving silver ions.  Artisans would paint the front of a piece with black enamel to outline a shape.  On the back of the piece the staining mixture would be applied.  These days the staining mix consists of silver nitrate combined with clay and oil or water and can be brushed on to the back of the glass piece.  The ability to apply the stain by brush lets artist use it not just for large areas, but for more subtle looks in hair, crowns, or halos. 

Bring on the Heat

The stained piece is then fired in a kiln.  The heat helps the silver ions move into and become part of the glass.  Once cooled and washed, the glass has a color from pale yellow to deep amber depending on the temperature and firing time.  That is, it has a yellow “stain” that is a permanent part of the glass surface.

Going Green

Silver stain isn't only used to give yellow colors. Green is the color seen when silver stain is applied to back of a piece of blue glass. When the sun shines through, the yellow stain filters out the blue part of the light while the blue color in the glass filters out the red. This leaves a lovely green that is perfect for grass and also for robes or gems in a crown.