Scratched/Bloomed Instrument Glass or Plastic?

...Before you try to remove any scratching or obscuration of the glass in instruments.....

Check it is Glass first!!!

Later lucas and other instruments may have PLASTIC faces and the use of Scotchbrite pads which (may) work on glass and/or other polishing media for GLASS may DESTROY plastic

One possible for plastic faces is BRASSO the metal polish and preferred tipple of "men of the road", it appears this is soft enough to be used on plastic instrument faces and will remove opacity ( light scratching)

This is the PLASTIC face of an oil temperature gauge damaged by attempted scratch removal using a ScotchBrite cleaning pad	This is the PLASTIC face of an oil temperature gauge damaged by attempted scratch removal AFTER 2 minutes of polishing with BRASSO METAL POLISH and subsequent polishing

Commercial scratch removal processes for windcreens may work on glass faces but remember, if you get liquid or pastes INSIDE the gauge they may not be removable and can discolour the interior and/or stop the fine mechanisms inside from working!

Many polishes though clear when WET may DRY as a powder..... be careful not to spoil the look of your gauge

Some glass faces on higher end gauges may be removed for [treatment in safety] with care either by rotating a bayonet fitting holding them in OR by carefully levering up the very fragile looking folded metal tabs around the retaining ring.

Replacement chrome rings may also be found for sale for SOME gauges

Thanks to Martyn Walker & Nigel Burfoot for the Brasso tip

Peter Kay adds a word or two of caution to the "rush out and use Brasso" stance of this article:

A word of warning about using Brasso to remove blemishes from plastic. Firstly, there are several different types of Brasso on sale in the UK. They all bear the same name but some appear to be made in the Far East, with a paper sticker attached. I also have a can with a made in S Africa label. Believe me, they are of a different formulation to the UK variety. Some smell of ammonia, which used to be a characteristic of this product, but now this seems to have been deleted, or my 'smell buds' have gone to sleep. The caution concerns the solvent in the Brasso. I remember as a teenager making a plastic model aeroplane and trying to remove some dried cement from the cockpit canopy with brasso. This resulted in the whole canopy crazing and being completely ruined. Some plastics  are attacked by turpentine, which also seems to feature in Brasso and also by Ammonia. I use Plastic Polish, as I know was used for real aircraft canopies in my RAF days and now sold by the local MG specialist. (I will check the brand later if anyone is interested)  Perspex polish is also sold by any good Glass factor, this is in a small white tube and is very fine, hence entailing a lot of rubbing. I usualy start with the former and finish with the latter. if you can, please check your plastic for compatibility before going the whole hogg. You have been warned!