billb@teklabs.UUCP (Bill Beran) (06/29/84)
Scratches can certainly be polished out of plastic faceshields as
long as they can be layed out flat. I've been doing it for years, but
never had much success with the bubble shields.
What you need is:
Adrill press or variable speed drill motor
a polishing pad backup disc about 3 in. in diameter
a one in. thick piece of upholstery foam 3 in. in diameter
a piece of soft felt 3 in. in diameter
cerium oxide polishing compound
a jelly roll pan (a cookie sheet with sides)
paper towels
a few drops of liquid dishwashing detergent
determination (be not of faint heart! It works great!)
The only unusual items that might boggle people here are the
cerium oxide polishing compound and the polishing pad felt. If you
know a rock hound, you've got it made. Otherwise, you can get this stuff
from Edmund Scientific. It just occured to me that it might be poss-
ible to scrounge the cerium oxide out of an outfit that makes eyeglass
lenses. Ask your local optometrist. Soft felt from a yardgoods store
will probably work, but it might make fine hazy scratches. Optical
grade felt or rock polishing material would be much better.
Getting ready:
Glue the foam disc to the backup pad and the felt disc onto
the foam. Use a waterproof glue such as contact cement.
Make up a slurry of cerium oxide and water to about the
consistancy of light cream, and add a few drops of detergent. Keep
this stuff in a tightl sealed jar and only open it when you need it.
This is just to keep it clean and free of dirt and grit which will
cause scratches. I use a squirt bottle.
Wash the faceshield to get rid of bugs and dirt. (scratches
again) Lay it flat inthe jellyroll
pan on several layers of paper towel.
Doing it:
Pour a couple of tablespoons of slurry on the faceshield
and start polishing with the pad in the drill. use enough pressure to
compress the foam almost all the way. Keep the speed just below the
splatter point (no use making a mess). If you are using a drill press
lock the quill to the same point of foam compression with the shield
and pan underneath. The jus move the pad continuously over the face-
shield or slide the pan around under the polisher in the case of the
drill press. That's all there is to it! after a little experience,
you will know about how long to do it. I usually do the inside about
5 minutes and the outside somewhat longer, depending on the scratches
I'm trying to remove.
It really works, but don't expect to remove deep scratches or nicks.
It will return the clarity to nearly original condition, and ca be done
as many times as the faceshield will allow before waviness or big
gouges prevent. I've done it to a single shiel as many as 10 times.
You have to be dedicated, but at today's faceshield prices that
doesn't take too much impetus. Good luck! :-)
Ride safe!
Bill Beran
Imaging Research Lab
Tektronix
{decvax,ucbvax}
!tektronix!teklabs!billb