Black composite plate of the di-bond type is an excellent substitute for black glass used in making ambrotypes as it provides a deep black surface similar to the japanned iron used in ferrotypes. The plate itself is composed of two layers of blackened alluminium with a layer of plexi-grass between them.
Composite plates are much easier to use than glass. Owing to the protective plastic film they don't require the laborious cleaning and degreasing or any other preparatory steps. They also minimase the danger of the collodion layer becoming separated in processing while at the same time offering very deep black substrate
The plates are 18x24cm, 2mm thickness