|"Flight to Egypt"|
Looking at cross sections of medieval glass produced from the 12th through the 14th century, the striated red layer takes up about half of the body of the glass. Flashed red glass from later periods exhibits the red as only a very thin top layer similar to the flashed red being produced today. Modern flashed red lacks the striations found in the medieval period.
|Fragments of Medieval Red - Glencairn Museum|