Ground blue glass was indeed used as a blue pigment in the days before modern blues were introduced. Smalt is its name.
In a painting with a warm dominance (more yellow, red, orange and brown than anything else), greys made with white and black will read as if they were blue. In many instances, especially in Old Masters, the blues are made in this manner.
Virgil Elliott is the author of Traditional Oil Painting: Advanced Techniques and Concepts from the Renaissance to the Present, published in 2007 by Watson-Guptill Publications. He is one of ARC's <u>Living Masters</u>, and an active member of the ASTM Subcommittee on Artists' Paints and Materials. Images of some of his artworks can be seen in ARC's Gallery of Living Masters and on his own web site, www.virgilelliott.com.
