The Dichroic Process

used with permission from Kroma

Dichroic coatings are produced on a variety of glass materials. Originally developed as interference filters in scientific measuring and correction applications, they are a product of the technology called "thin film physics".

The coatings are quite thin, about 700 angstroms thick, and are generally constructed of silicon and titanium oxides evenly shuffled into multiple layers. These layers are applied by vacuum deposition and cause the glass to become a partial mirror by allowing only a select narrow band of light to transmit; other rays are rejected through reflection and absorption.

As the light rays transmit through the glass at a right angle they are less effected by refraction than when passing at an extreme off axis angle where they have to travel a greater distance through the coated material. This greater distance causes a shift of color and when dichroic glass is viewed at even slightly different angles, you will see differing colors.

Dichroic Glass	Transmits	Reflects
Additive Colors	Red	Aqua
	Green	Pink
	Blue	Gold
Subtractive Colors	Magenta	Green
	Yellow	Blue
	Cyan	Red