[RadioSvit]

Hello everybody . Colleagues, please share information if someone owns it - what types of varnishes were used by American manufacturers of radio cabinets in the 1930s? Shallac varnishes, alkyd, polyester, polyurethane or nitro varnishes? I will be grateful for any information.

[morzh]

Certainly NOT polyurethane.
I also doubt it was polyester as it is a pretty novel material and was not available until end of 20s-30s as it was still being worked on.
Nitro lacquers were available and saw their use booming displacing older types in 1920s.

[RadioSvit]

I think so too, Michael, but to my surprise I found that the varnish on the recently purchased RCA 9K strongly conflicts with nitro solvents and I could not varnish its top cover with nitrovarnish.
Is it really covered with shellac? Could it be that at that time there were still some unknown types of varnishes?

[morzh]

There are others here who will provide you with expert knowledge in lacquers/varnishes.
All I could say that there are still those "cowboy furniture restorers" that will take an old radio and polyurethane it. Then when they sell a radio to a person who wants to really do justice to the cabinet, that person will have to spend time and effort removing the polyurethane finish off of the cabinet. It is an extremely stubborn substance and is not removed easily.

[Phlogiston]

Shellac through the 1920's

Duco brand (DuPont) nitrocellulose lacquer through the 1930s.

The change from one to the other probably occurred in 1929. Some cabinets might have both - shellac topped by Lacquer.

The Germans were definitely using a poly-like product in the 1950s.

[RadioSvit]

Thank you, Russell. So, if I understood correctly, in 1936 only nitrocellulose varnish could be used with a small possibility of encountering shellac. Then another question - what can be the reaction to nitro solvent on shellac? On my console, at the point of contact with the solvent, the varnish partially dissolved and white spots appeared. I suspect it's shellac after all.

[John Bartley]

Lacquer, lacquer, lacquer, lacquer .... and lacquer. (You specified 1930's).

[Phlogiston]

The solvent in shellac is denatured alcohol.

Lacquer thinner is mostly toluene and acetone.

Some people use shellac as a sanding sealer/filler, topped with lacquer. I don't know how many companies used that combination.

[Brad Winder]

It's possible someone used another polish or protectant product on your radio later in it's life, and that is what is reacting when you try to remove the finish. I know there are some "restoration" products that are a no-no to use, if you want to refinish your radio or furniture in the future. Products with silicone in them are bad...

[RadioSvit]

Russel, Brad Winder... Thank you friends. This is important information and I will take it into account.