Here is some info I have in my notes on Rotol props.
The Rotol colour code for the disc changed at some point post-war (1946?), but I am not sure exactly when.
The original Rotol disc colour code:
Wood
White____Rotol manufactured Jablo blades with Rotoloid covering
Pink_____F. Hills & Son manufactured Jablo blades with one of three coverings - either Jablo (covering), Venus, or Cristofin
Green___ Hordern-Richmond manufactured Hydulignum blades with one of two coverings - either Rotoloid or Cristofin
Yellow___Weybridge/Airscrew Company Ltd. manufactured Spruce blades with one of three coverings - either Rayoid, Schwarz, or Acetate
Metal
White____Rotol manufactured Aluminum blades
Lt. Blue__Curtiss manufactured Aluminum or Steel blades
The revised Rotol disc colour code:
Pink for Jablo blades with one of three coverings, either Rotoloid, Jablo (covering), or Cristofin
Green for Hydulignum blades with one of two coverings, either Rotoloid or Cristofin
Yellow for Spruce blades with one of three coverings, either Rotoloid, Schwarz, or Cristofin
Coverings
Rayoid is a cellulose nitrate thermoplastic. It was used in sheet form, heated and pressed onto the surface of the wood blade, with the Rayoid bonding to the surface of the wood.
Acetate (covering) is a cellulose acetate thermoplastic, cheaper to produce than the Rayoid cellulose nitrate thermoplastic, and more easily applied to wood. It can be applied either in sheet form by heating and pressing, or as a liquid paint when suitable solvents are used.
Cristofin (Crystaline finish) was a variant of Formvar™ (polyvinyl formal varnish), a synthetic resin made into a varnish. It was painted in multiple layers onto the wood surface of the blade and bonded to the wood surface. It dried hard and very clear.
Rotoloid was a combination of materials - a fine phosphor-bronze 'gauze' was wrapped around the wood blade, then Rayoid sheet was heated and pressed onto the surface under high pressure, the Rayoid flowing penetrating/permeating/encasing the phosphor-bronze 'gauze' and bonding to the wood surface. (Note: The info I have seems to indicate that sometime post-war, the meaning of Rotoloid covering became synonymous with simple Rayoid covering. The term Jablo covering, and the materials/process it describes below, then became the standard when including phosphor-bronze 'gauze'.)
Jablo (covering) was a combination of materials similar in structure to Rotoloid - a fine phosphor-bronze 'gauze' was wrapped around the wood blade, but then the blade was painted with a varnish similar to Cristofin (maybe actually Cristofin) which penetrated/permeated/encased the 'gauze' and bonded to the wood surface of the blade. Multiple layers of the varnish were applied to build up a smooth contour.
Schwarz covering was a layer of linen cloth wrapped around the blade with a cellulose acetate thermoplastic heated and pressed onto the surface of the cloth, with the plastic penetrating/permeating/encasing the cloth and bonding to the wood surface of the blade.
I do not have any information on the Venus covering other than it was a synthetic resin varnish that was brushed on in multiple layers to build up a smooth contour.
