Remove scratches from meter lenses?

[Axtman]

What is the best method to remove light scratches from clear plastic multimeter lenses? Thanks.

[jfphp]

There is a lot of polishing medias for car's bodies : some are very "hard" to remove deep scratches and others are mild just to get a shiny finish. But be aware that this produts contain sand or something like with various diameters and at the end the big scratch has disappeared but under raking light you will see a lot a very fine scratches. You can then polish with special products for silver or metal  (based on cotton) but try before if the product will not melt the plastic. I know a lot of products but I am in...France. Beware of static electricity when polishing and short the meter.

[chris_leyson]

"Brasso" metal polish is very good for removing scratches from acrylic. The abraisive is silica, or quartz if you buy it in Australia. Think it's available in the US but there are probably suitable alternatives.

[Rerouter]

I would say brasso, it depends a little on the depth, for deeper scratches brasso will tend to round over the edges so they are less noticeable, but they are still there.

Word of warning, superglue, and standard window repair fluids don't exactly polish if your trying to fill a deep scratch, and most of the plastic ones have a strong enough solvent to make the plastic cloudy.

And final note, if its a UV sensitive plastic, that was coated rather than being in the mix, (you will see a coating being broken if you polish them), then you either need to re coat it in a UV lacquer or be prepared to keep it out of the sun.

[ArthurDent]

Some of the car headlight lens restoring products may work better than the body buffing products as they are designed to work on plastic. I had used one headlight lens kit and removed a big scratch but it took some time. If you don't spend enough time using the finer and finer polishes you can end up with a slightly foggy appearance. Some recommend carefully using a clear spray overcoat to fill in any microscopic scratches but you have to be careful and use a light coating so it doesn't run and you have to start over. I dismantled the DMM so I was just working with the lens and didn't have to worry about messing the case up.  Don't get impatient and use a drill with a polishing disk as the polishing speed may cause enough heating to distort/destroy the lens.

[SeanB]

Deep scratches you would be best to wash it clear with some solvent ( careful, most of these windows are either polycarbonate, which does not dissolve in ethanol, or polystyrene, which does dissolve in ethanol and almost every solvent) and dry it, then apply a small amount of UV curing glass clear resin to fill the deep scratch, and then use a gentle abrasive, something like acrylic headlight polish for cars, and then gently level off the scratch till the surface is smooth again. Small scratches just the headlamp polish, and if polycarbonate and with no anti reflective coatings on it you can use a soft lint free cotton cloth ( a well used white t shirt that you no longer like is a good source, but microfibre glasses cleaning cloths are also good) to apply the polish. and buff it off.

[drussell]

Novus... 

Novus #2 is generally sufficient for most things like meter faces, antique radio bits, etc.  You can follow with #1 if you want to get a really glossy polish on something but even just having #2 around is super handy.  They also make #3 but you can also just use automotive polishing compounds or rubbing compound if you need a really harsh polish to begin with on badly scratched surfaces that can withstand it.  The tubs of Turtle Wax red (rubbing) & green (polishing) are widely available and very inexpensive.  (Work great on the car, too!  )

I first learned about Novus watching bandersentv's restoration videos on youtube but have since seen it all over the place.  Great stuff for plastics!

[daedalux]

Such things are all polished nicely with polishing pastes about 1500-2000 grit and a cotton ball before lightly cleaning with alcohol.

[mgl99]

I use Novus #2 for applications such as this.

[edavid]

Obviously Novus polish is good, but many DMM windows are so soft that you can use toothpaste.

[james_s]

I've found that Novus is as good as anything else I've tried. It was designed for motorcycle windshields but works on most plastics. A random orbit buffer can save you a lot of elbow grease, just be careful not to melt the plastic. Patience is key.