The first step is to remove the major or scratches and damage. I start with 400 to 600 grit wet/dry sandpaper taped to a flat surface. A piece of glass works well but I find a slick 12x12 inch ceramic tile to be prefect, it’s heavier and less likely to break than glass. I choose the grade of sandpaper based on the damage to the lens, the deeper and more extensive the damage the coarser the grain I start with but I would not suggest much more than 400, otherwise you will be causing a lot more scratches you will have to later remove. Depending on the lens damage you may need/want to polish the lens with increasing grits of paper, on this lens 600 followed by 2000 was OK. Once I have all of the scratches and damage remove I switch to a much finer grit, usually 2000 to get the intermediate finish. This finish should be a fairly even milky white with faint scratch lines, your first reactions should be that you have made things much worse..don’t worry, you haven’t. When sanding use lots of water to keep down heat, MOVE IN A FIGURE 8 PATTERN keeping even pressure on the lens. DO NOT use one linear or circular motion and DO rotate the lens around, the objective is to keep the polishing as even across the lens as possible.
Once you have completed the final sandpaper polishing you should have a lens that looks something like this.
Next you do the final polish. In the past I have used auto finish buffing compound and a cloth wheel on a Dremel tool. This works well but can messy and many may not have Dremel tool. I found an alternative that worked very well and requires no additional tools than the 12x12 tile used earlier. I wrapped the tile in one layer of an old but clean t-shirt, wet it then soaked it in a plastic headlight restoring compound (both it and the wet/dry sandpaper can be gotten at any auto supply). After you have the scratches out you can buff the lens farther by rubbing it briskly on the dry surfaces of the same T-shirt, just be careful not to overheat it.
The finished product. I did not remove all the scratches since this will be a working gauge and will likely get scratched up soon anyway but as you can see it is much better. The entire process took 15-20 minutes, it is possible to remove all the scratches and have a like new finish if you care to take the time.
By Herman Mowrey…..Brought to you by Vintage Double Hose. www.vintagedoublehose.com