It is interesting that flashed glass was first used in stained glass windows long after it had been used in the making of bottles and vases, etc. A beautiful example of early flashed glass is the Portland vase in the British Museum, a fabulous example of Roman cameo glass, probably made in Italy and dating to between 5AD and 25AD.
Portland vase in the British Museum – © Marie-Lan Nguyen / Wikimedia Commons
The Glasgow has several beautiful Chinese cameo glass snuff bottles with two shown below. Tobacco arrived in China in the late 16th century and the taking of powdered tobacco, snuff, was very popular by the late 17th century. Snuff bottles were an excellent way of keeping it fresh and the 18th and 19th centuries saw the production of the finest snuff bottles. They were made of a variety of materials, flashed glass being a very popular type.
The grinding technique described above is seen in many of the heraldic stained glass windows in the Burrell Collection. A superb example, currently on display in a specially designed light-box so you can study the techniques, is the shield of Sir Thomas Harrowdon, Great-uncle of Sir Edmund Knightley, made around 1530. This piece of heraldic stained glass is from a collection of panels from Fawsley Hall depicting the lineage of Sir Edmund Knightley. The red and white chequered background is made from red on clear flash glass which has been carefully abraded to produce the pattern.
Silver stain was often applied to the back of a piece of abraded flashed glass in order to produce a yellow colour. Above is a detail from the lower centre of the shield. The top detail is
lit from behind (transmitted light), the way it would be viewed as a window, and the lower from above (reflected light) which shows the detail of how it was ground out. The flashed glass used for this piece is the same as that used for the chequered squares; layer of red on a layer of clear glass. Silver stain has been applied to the back of the glass where the red layer has been abraded away to turn the clear glass yellow.