Enhancing a Saw Etch

Often, an etch may be faint or be hard to read after cleaning rust and dirt from a saw plate. Sometimes the etch has already been obliterated by the action of the rust or was never very deep to begin with. Not much can be done with these. However, some etches can be made more visible by improving the contrast in the etch itself.

Start with a clean saw plate, preferably by sanding with fine paper, followed by metal polish. Take care to clean around and over the etch by removing as little as possible.
The first step is to thoroughly degrease the metal using acetone or mineral spirits. Put the solvent on a clean cotton cloth and wipe in one direction only. Wipe again with a clean cloth soaked in solvent. Let dry.
Next, apply a paste or gel-type cold gun bluing using a brush or a cotton cloth. 
Cover the area of the etch completely and evenly, covering an area slightly larger than the etch. Let dry completely.
Let the bluing dry thoroughly. Do not touch it as the chemical is "rusting" the plate. Disturbing it will create spots or uneven areas.
Once dry, use a hard rubber sanding block with 600 grit or finer paper and lightly swipe the area once or twice. Wipe away the dust and repeat as necessary to remove the bluing from the high areas, while leaving it in the bottom of the etch. Go slowly and stop when the etch is fully revealed. One swipe too many may obliterate it.
Take a close look at the area. It may be necessary to blend the edges where the bluing was applied. Do this with the sanding block or with sandpaper wrapped around your fingers. Do not touch the etch.
If all goes well, the etch will be darker and more readable. In this example, the words "Simonds Mfg Co" are only slightly darker than before, but it is what it is. The etch was probably not made to uniform depth at the factory.
Here is the etch again before it was treated. Not perfect, but some definite improvement. Not bad for a saw that had been so rusty that no etch was visible at all.
Note that the bluing will often create a halo that can be seen in varying light. This effect can be minimized by bluing the entire side of the saw and sanding it away as before.