Expert: Greg Scholl - 12/9/2009

Question
I am trying to strip several metal door frames and one door in my apartment.  I was able to remove most of the paint w/ a paint stripping solvent, but I have now hit a green coat of something that is not paint.  The coating is extremely hard. I believe the door frames and front door are original to the apartment which was built in the late 1920s.  Do you have any idea what the coating might be and how I should try to remove it?   Thank you for your help.  

Answer
Hi Colette, are you using an actual paste type paint stripper? There were only a few coatings at that time, and it's likely an enamel or maybe even lacquer and a Methylene Chloride paint stripper should strip it fine...but it may not. There was a lot of chemical and coatings experimentation and development being done at that time, while I tend not to use other's explanations when answering questions...this kind of helps sum it up as to what was going on in those days, and if you're confused....join the club..:

"Developments in alkyd resins resulted in the formulation of various types, including drying-oil and non-drying-oil modified, natural-resin-modified, phenol-modified, phenol-modified and oil-extended, and urea-modified types. Combinations of these resin mixtures were also produced.

A key early breakthrough for alkyd resins came with the use of rosin-modified and non-drying-oil alkyds in nitrocellulose lacquers used for automobile finishing in the 1920s. The alkyd addition improved adhesion of the lacquers.

Commercialization of alkyd resins was given a boost in 1916, when the Gibbs-Conover process for the manufacture of phthalic anhydride from naphthalene was introduced, significantly reducing phthalic anhydride costs. Important later developments included the commercial introduction of pentaerythritol based on formaldehyde and acetaldehyde in the 1930's, and trimethylols of propane and ethanes. Coatings based on alkyds found a great range of applications, in both air-dry and baking finishes, due to the superior performance of these coatings in terms of long-term appearance and durability properties. These uses included finishes for transportation equipment, railway and street cars, buses, autos, trucks, metal signs, farm implements, fencing, appliances, and in roof, marine, architectural coatings, and other applications too numerous to list.While alkyds are essentially resins of a polyester type, the term alkyd usually refers to polyesters that are modified with a triglyceride oil or the acids of such an oil."

In short,as you can see, it's difficult to know exactly what you may have found there, and it may be very difficult to remove without a sandblaster or other mechanical means....it might pay to talk to a stripping place in your area, that might be familiar with the industrial coatings that were used in that area, in that era....wish I could help more- post back if need be- regards- Greg