These are some notes from the Burke 116 chair paint preparation process.
A lot of the approach depends on the equipment and supplies you have available, but I’ve found that the best way to look at the problem of paint preparation is to view the Burke chair as two very different materials – Aluminum alloy and Fiberglass.
In this case, I’m using a 2-part epoxy that etches a material’s surface. This means removing any foreign substances from the surfaces so that it’s bare alloy metal and bare fiberglass. In the case of fiberglass there is the additional consideration of foreign substances that may have penetrated beneath the surface of the fiberglass that would present dissatisfaction with the painting result down the road.
Removing the paint from the Burke chair pedestal was an eye-opener. First, no paint remover would work on the pedestal’s paint. After drenching one of the pedestals in paint stripper for 2 days, I noticed the paint had lifted from the end of one of the feet as depicted in one of the pictures. This allowed the use of a sturdy 2" wide scraper to chisel away the paint. There are 2 observations here: The first thing noticed is that the paint type Burke, Inc. used is an unusually thick latex. After so many years, the latex’s binder was sticking to the aluminum but because the binder leeched out of the latex, allowing a slow chiseling process that saved having to take a chance on a mechanical sander. To give you an idea, removing the paint by scraping took about 15 minutes for each of the pedestal feet, and about an hour for the pedestal trunk.
Removing the paint from the outside of the flange was a different matter. The composition of the paint was either different, or it was applied differently. This meant hand sanding the flange. The best process found for hand sanding was to start with 80 grit sandpaper to first thin the paint’s thickness, then, as you begin to see metal, move to an adjacent section of the flange, etc., until the entire surface paint is near metal. To best get the remaining paint without taking some metal with it is to switchover to 180 grit sandpaper. To give you an idea, each flange takes about an hour to complete.
The most important mechanical improvement I’ve encountered thus far is to chase the threads in the pedestal casting’s four receivers. In this instance it took a 10-24 thread tap. The reason I decided to halt the paint preparation process and chase these threads was that I noticed a couple of the machine screws were difficult to remove. The reason is that the original equipment machine screws are the self-tapping type, indicated by a groove cut into the last few tapered-off threads. These machine screws are replaced by stainless steel hardware in this build. While the flange was dissembled for sanding, I took a good look at the machine screw bores in the pedestal casting. It’s noted here that there are a couple of reasons why both the original equipment machine screws and the stainless steel replacement screws don’t like to torque down or remove easily. The first possibility is that there’s corrosion interfering, there’s deformed threading, or there is some premature bottoming out going on. First of all, taking one of the exactly matched stainless steel machine screw replacements and seeing how well they fit in the four holes, I determined that if the machine screws would not turn by hand from start to bottoming out then the mechanical condition was deemed unacceptable.
To get the machine screws to operate freely in the pedestal mounting holes, I soaked the holes overnight in gasoline and blew them out the next morning. Then, using a 10-24 thread tap (see photos), I chased these threads and removed a lot of metal particles in the process. This meant that the tap was having to do a lot of re-cutting of the threads. Then I had to flush the holes out with solvent. I tested the new stainless machine screws each time and it took about 3 separate taps of each hole to be able to freely hand twist the machine screws into the holes. I also noted that there was no lash going on with the machine screws after the first thread indicating that it was a really good fit. I cleaned up everything, put a light coat of machine oil on the new machine screw threads, and it was by all indications a perfect mechanical fit. One of the problems of oiling threads is that if you apply too much oil, threaded fasteners will bottom-out prematurely because you can’t compress a fluid.
Then I went to tighten down the flange assembly to the pedestal, and what a remarkable difference it was… I highly recommend this exact process for all Burke chair threads.