Polishing a plastic case.

[saddlestone-man]

What's the best way to polish out some slight scratches and generally bring up the appearance of a plastic (not bakelite) case on a radio?

[Boom]

#5 paste works just as well on plastic as Bakelite.

[whcureton]

Hello Saddlestone
This is a tricky business because if you use any motorized type buffer you run the risk of "burning" the plastic and ruining it for good. And NEVER use any solvent based cleaners. Soap and water for plastic. The best course of action, whichever compound you use, is to work it by hand. The depth and type of scratches will determine which compound or collection of coumpounds you should use.

So, my recommendation is easy does it. Begin working with the mildest abrasive pastes beginning with the finest you can find (liquid carnauba wax, usually pink in colour, is about the mildest I can think of). I use it often on my clock cases and metal parts and I've used it on some smooth plastic pieces on other items. This is, as it's name implies, a wax and it is usually used on fine paint on automobiles. Microscopically, it is still an abrasive.

Another option is to try an actual plastic polish like the Novus product. This is for fine scratches. Again, only apply it and work it in by hand with good quality soft rags or towels.

An example of a seemingly mild abrasive compound you might want to experiment with if some of your scratches are deep is common household toothpaste. Toothpaste is actully quite abrasive in the grand scheme of things.

The initial state (or severity) of your scratches will determine which order and combination of abrasives you should use. Remember, you are trying to make a scratch in a hard surface disappear so you will have to take some of it's surrounding material away, at least down to the level of the deepest valleys, and then polish the surrounding area out to blend into your finish. Experts can even polish out scratches in clear plastics using this approach. Amazing, eh?

Finally, before you begin see if you can determine how your plastic case was moulded, look at exposed edges or corners or the rear panels and try to see if the case is of the same colour and consistency all the way through it's thickness. Be careful not to start polishing on a "coated" or layered surface over a substrate, you know what I mean, like sanding too deep on a veneered wood surface and you hit the substrate.

A long-shot approach would be to find some plastic filler material that can be buffed down after filling the scratches but to be honest, this is like trying to repair porcelain. It never matches. Of course if you are going to paint or coat your case afterwards this won't matter, but I don't think this I what you are trying to accomplish.
Good luck!
- Bill in northern California

[Mike Phelan]

The term "plastic" covers many different substances and can require different approaches.

Different grades of rubbing compounds obtained from motor factors can get the deepest scratches off, followed by toothpaste and metal polish.

There's also this.

[mike_newcomb]

I use kitchen roll, dampened with surgical spirit.

Roll must be white, otherwise colour can transfer to object being cleaned/polished and then be difficult/impossible to remove, as plastic is not glass and can be slightly porous.

Best to try on small test area first where if there is a problem, it will not show subsequently.

Avoid contact with any printing or labels, as these can be damaged or removed.

If scratch is too deep this method may not remove completely. Works well on mobile phone screens.

Best price for small bottle (200ml) of surgical spirit is in cheapo stores (e.g. 99p), then Savers.

Good Luck - Mike

[saddlestone-man]

Thanks for all the good advice. I've just ordered a tube of Greygates No 5 from eBay.

The case I want to polish is a Pye R33 - a nice burgundy sort of colour - that needs a few scratches removing and the shine bringing back to it.

I'll let you know how it goes. Need to take some 'before' photos so I can see the effect.

best regards ... Stef

[Alistair D]

Mike,
would I.P.A. work or is there something special in Surgical spirit? Is this method only for very fine scratches or can it cope with deeper ones?

Al

[HamishBoxer]

Paste Polishing No 5 or Bakobrite, sold by Chas E Miller is the stuff.

[mike_newcomb]

Hi Alistair,

I have had success with surgical spirit in completely removing fine scratches from mobile phone screens, etc.

Deep scratches are different, in that to eradicate requires much surrounding material to be removed. Suggest trying s p and check results.

Perhaps one of the more abrasive polishes recommended by others here, is better for the task.

Please advise back on progress.

Good Luck - Mike

[crackle]

Just a word of warning, I tried to polish out some scratches on an old plastic case, using both Bakelite polish and brasso, and the scratches went but the finish never matched the surrounding. It was not an issue with the colour more the texture, I could not get a full shine back on the bit where I had been polishing with paste.
The surface of the plastic seemed to be a different texture, hard and denser, to the core of the plastic which seemed to be a softer material.
Mike