Many of the screws
had surface rust. To bring back the original look, the screw has to be completely
re-surfaced. This involves removing the rust and bringing back the polished surface
through various grades of wet dry sandpaper and then a buffer wheel. It is then carefully
cleaned in solvent to remove any polishing compound. The highly polished metal surface is
heated with a heat gun. The surface will first turn a straw -yellow color and then
progress to a blue and then deep purple blue color in rapid succession. At just the right
moment the screw is quenched in oil to stop the color turning process. If the part is
over-heated, the deep blue disappears into a light sky-blue. The process must be done
seamlessly from start to finish. If the screw is over-heated the color cannot be reversed.
The part must be stripped, re-polished and heated again. One can usually get a
satisfactory result when re-doing an original part. However, it is important to remember
that if you are replacing any parts, for example replacing missing screws, check
first to see if that part will blue upon heating. Most newer screws are made with modern,
low carbon alloys that will not respond well to this process; they will not turn blue.