UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > General Vintage Technology Discussions

Notices

General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc.

Closed Thread
 
Thread Tools
Old 26th Mar 2019, 10:17 am   #21
YoungManGW
Hexode
 
YoungManGW's Avatar
 
Join Date: Dec 2011
Location: Oswestry, Shropshire, UK.
Posts: 408
Default Re: Polishing old cloudy transparent plastics

Toothpaste works a treat.
Regards,
Richard
YoungManGW is offline  
Old 26th Mar 2019, 10:21 am   #22
ajgriff
Nonode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
Default Re: Polishing old cloudy transparent plastics

Quote:
Originally Posted by Terry_VK5TM View Post
Many years ago, we used to use toothpaste on Arcade machine perspex.

May not work now with the change in toothpaste formulations
Modern toothpastes still contain mild abrasives and can be used for final polishing of plastic. Eucryl Smokers Toothpowder is slightly more aggressive and is still available cheaply in the UK.

Alan
ajgriff is offline  
Old 26th Mar 2019, 10:56 am   #23
Skywave
Rest in Peace
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
Arrow Re: Polishing old cloudy transparent plastics

Quote:
This is the same issue as with Bush TR82s, where the large transparent knob, (sometimes incorrectly described as the 'dial') goes milky right through and no amount of polishing makes an iota of difference
Quote:
Originally Posted by Karen O View Post
I wish I'd known that seven years ago! I spent a whole weekend polishing away at my TR82C knob with nothing to show
Ditto here! I have TR82 in same condition; been here for ages. I've often thought about how to fabricate a replacement transparent knob, but doing that will be v. difficult - and for me, simply not worth the huge effort trying to achieve a satisfactory result - if one is achievable at all!

Al.
Skywave is offline  
Old 26th Mar 2019, 12:00 pm   #24
Junk Box Nick
Octode
 
Junk Box Nick's Avatar
 
Join Date: Jun 2011
Location: West Midlands, UK.
Posts: 1,571
Default Re: Polishing old cloudy transparent plastics

Quote:
Originally Posted by yesnaby View Post
Edd from Wheeler Dealers did this successfully to car headlights, though the process started by sanding them to become very rough and matt, then several stages with finer and finer sanding/polishing. Seemed to work well.
I have used this process on headlight lenses with success using very fine grades of wet and dry paper.
Junk Box Nick is offline  
Old 26th Mar 2019, 12:00 pm   #25
ajgriff
Nonode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
Default Re: Polishing old cloudy transparent plastics

The principle abrasive used in proprietary plastic polishes is cerium oxide. This can be acquired economically (minimal packaging and marketing hype) in the form of a white powder. I bought 50g for £5 about five years ago which may sound a lot for a couple of teaspoons full but it really does go a long way. From memory I've used it to remove scratches from and polish turntable covers, meter lenses, CDs, bakelite 'phones, plastic 'phones, aluminium trim, sheet steel, car light lenses, mirrors & a car windscreen. All this and I still have about 10g left. Incidentally, power tools are a practical necessity for glass but plastics and soft metals must be done manually.

Tractionist also mentioned using wet & dry paper for deeper scratches ie, ones you can feel with a thumbnail, which is realy the only way to approach the problem. It does take a leap of faith to see a transparent surface turning opaque as a deep scratch is erased. However, it's very satisfying when bright and shiny transparency is restored with polishing. The abrasive used for wet & dry paper is usualy silicon carbide which is an exremely hard compound just like cerium oxide. The difference between them is that the carbide particles have a sharp jagged surface whereas the oxide particles are smooth and rounded.

Alan
ajgriff is offline  
Old 26th Mar 2019, 1:38 pm   #26
mole42uk
Nonode
 
mole42uk's Avatar
 
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,608
Default Re: Polishing old cloudy transparent plastics

I second the use of Brasso, used it on several of my Heathkit meters with excellent results.
__________________
Richard

Index:
recursive loop: see recursive loop
mole42uk is offline  
Old 26th Mar 2019, 2:35 pm   #27
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
Default Re: Polishing old cloudy transparent plastics

Have just tried brasso ironically on a junk Heathkit GDO knob (the big plastic bit). My word that works pretty well so far!

Am using a cheap Tesco microfibre cloth with it.
MrBungle is offline  
Old 26th Mar 2019, 2:58 pm   #28
ekjdm14
Banned
 
Join Date: Feb 2019
Location: Congleton, Cheshire, UK.
Posts: 609
Default Re: Polishing old cloudy transparent plastics

I've used Brasso with great effect years ago on a Perspex ve*icle window that was completely yellow/opaque and "gritty" feeling. Have used it to good effect on other automotive related things too & would suggest it's likely to be good for this hobby also. With the caveat of trying on a small area first to make sure not to kill a rare part, and protecting with plastic polish afterwards.
ekjdm14 is offline  
Old 26th Mar 2019, 3:02 pm   #29
mole42uk
Nonode
 
mole42uk's Avatar
 
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,608
Default Re: Polishing old cloudy transparent plastics

After the Brasso treatment, I use some Pledge furniture polish, sprayed lightly onto a cotton duster, to wipe over the surface. It keeps the gleam for ages!
__________________
Richard

Index:
recursive loop: see recursive loop
mole42uk is offline  
Old 26th Mar 2019, 3:06 pm   #30
Glowing Bits!
Octode
 
Glowing Bits!'s Avatar
 
Join Date: Oct 2011
Location: Wrexham, North Wales, UK.
Posts: 1,457
Default Re: Polishing old cloudy transparent plastics

Brasso is good for removing most of the yellowing.
For better, long lasting results, wash the plastic to remove Brasso traces, then spray on a bit of Plexus followed by a quick buff, the finish will stay shiny for a good deal of time.
I'm going to see how long it takes someone to ask what the magic spray is, it's a secret!
Rick.
Glowing Bits! is offline  
Old 26th Mar 2019, 3:10 pm   #31
Glowing Bits!
Octode
 
Glowing Bits!'s Avatar
 
Join Date: Oct 2011
Location: Wrexham, North Wales, UK.
Posts: 1,457
Default Re: Polishing old cloudy transparent plastics

Here is an MB60 dial (the TR82 but earlier) after the Brasso treatment, it was yellow to the point of being useless.
Attached Thumbnails
Click image for larger version

Name:	20190326_140753.jpg
Views:	129
Size:	67.7 KB
ID:	180464  
Glowing Bits! is offline  
Old 26th Mar 2019, 3:37 pm   #32
ITAM805
Nonode
 
ITAM805's Avatar
 
Join Date: Jul 2010
Location: Folkestone, Kent, UK.
Posts: 2,172
Default Re: Polishing old cloudy transparent plastics

Quote:
Edd from Wheeler Dealers did this successfully to car headlights, though the process started by sanding them to become very rough and matt, then several stages with finer and finer sanding/polishing
I did my badly yellowed Astra headlights the same way and finished off with mag wheel polish applied to a damp buffing mop, worked a treat
ITAM805 is offline  
Old 26th Mar 2019, 7:05 pm   #33
Bazz4CQJ
Dekatron
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,934
Default Re: Polishing old cloudy transparent plastics

I've just spent a few minutes on Google re "polishing plastics"; there are numerous threads, many to do with car headlights, caravan plastic windows etc. There seems to be little consensus. Some think that T-cut is wonderful, others say that it (and Brasso) contain too much ammonia which is bad. Some say cerium oxide is good on plastic, others that it should only be used on glass. I guess that one issue here is that there are quite a lot of plastics and we seldom know for sure which one we are dealing with.

B
__________________
Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.
Bazz4CQJ is offline  
Old 26th Mar 2019, 8:37 pm   #34
Uncle Bulgaria
Nonode
 
Uncle Bulgaria's Avatar
 
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,329
Default Re: Polishing old cloudy transparent plastics

I'll reiterate my previous post that Brasso/Silvo causes crazing - I just tried it on some acrylic in case my previous experience wasn't because of the polish but some other effect. Even during the polishing, micro-cracks appeared on the edges, so do test before trying it out! No doubt the particular type of plastic being polished matters too.

I'm going to try getting hold of some cerium oxide, which sounds the bee's knees. ajgriff - did you mix it with water?
Uncle Bulgaria is offline  
Old 26th Mar 2019, 8:37 pm   #35
ajgriff
Nonode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
Default Re: Polishing old cloudy transparent plastics

Quote:
Originally Posted by Bazz4CQJ View Post

Some say cerium oxide is good on plastic, others that it should only be used on glass.

B
Just like wet & dry paper cerium oxide comes in different grades from coarse to fine. Vendors of the coarser auto-glass grades warn that their product may leave fine scratches on softer materials like plastics. In theory for badly scratched plastic you would work through the grades finishing with very fine for an 'optical' finish. In practice this is completely unnecessary for most purposes. My 50g packet (see earlier post) is a medium coarse glass grade and produces an excellent finish on plastics without further polishing. This can be improved slightly by finishing off with T-Cut, Brasso or even toothpaste depending on how far you wish to go. Happy to take some photos of my efforts if there is sufficient interest.

Alan

PS The perceived wisdom with cerium oxide is that you make a paste with water. However, I use a damp cloth and increase the wetness as I go which seems to work well. Just leave any unused powder to dry out for future use.

Last edited by ajgriff; 26th Mar 2019 at 8:48 pm. Reason: Added PS
ajgriff is offline  
Old 26th Mar 2019, 8:46 pm   #36
Argus25
No Longer a Member
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Polishing old cloudy transparent plastics

The real answer to this question depends on what kind of finish you are satisfied with.

Brasso for example gives a about as coarse a result as the coarse grade of the Novus polish I cited. That is nowhere near good enough for a mirror quality finish. This is why if you then add another masking compound like furniture polish to the surface it looks more glossy and masks the fine scratches from the abrasive in the Brasso .

If adding any kind of surface oil improves the appearance, it is just an indication that the polishing job is inadequate and the surface still is too rough. So like I say, if you want the best possible job, get the Novus, if you are happy with an inferior result, go ahead and use the Brasso.
Argus25 is offline  
Old 26th Mar 2019, 8:57 pm   #37
ajgriff
Nonode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
Default Re: Polishing old cloudy transparent plastics

I would guess that Novus contains a very fine optical grade of cerium oxide.

Alan
ajgriff is offline  
Old 26th Mar 2019, 9:00 pm   #38
Graham G3ZVT
Dekatron
 
Graham G3ZVT's Avatar
 
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,710
Default Re: Polishing old cloudy transparent plastics

I polished the lens of a Sony Xperia smartphone with Silvo wadding. I had to rub it very aggressively and didn't think it would end too well.

By lens I mean the exposed part that is really a filter for protection rather than the actual lens. The phone was a replacement from my company and the previous owner did not look after it, and allowed the lens to rub against a hard surface.

The images all looked as if they were taken through a gauze. Close inspection suggested that the damage was to the photochromic coating, so my intent was to remove it completely.

It worked beyond expectations and the camera was as good as the original one. The loss of the coating had no detrimental effect.
__________________
--
Graham.
G3ZVT
Graham G3ZVT is offline  
Old 26th Mar 2019, 9:50 pm   #39
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
Default Re: Polishing old cloudy transparent plastics

Well time to report an outcome. I picked the GDO I am in the middle of re-kitting and used Brasso and a microfibre cloth then used toothpaste (standard Aquafresh) to finish it off. About 20 minutes of polishing and I got this which I'm extremely happy with.

Before:

Click image for larger version

Name:	gdm-before.jpg
Views:	213
Size:	80.7 KB
ID:	180491

After:

Click image for larger version

Name:	gdm-complete.jpg
Views:	204
Size:	55.1 KB
ID:	180485

I made a new scale by scanning the old one at 1200dpi, set hue to mostly yellow, then increase saturation, convert to two bits (B&W) and laboriously cleaning up the image in gimp on Linux. Printed on the back of a Chartwell log/log paper pad sheet with an inkjet.
MrBungle is offline  
Old 27th Mar 2019, 7:11 am   #40
mole42uk
Nonode
 
mole42uk's Avatar
 
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,608
Default Re: Polishing old cloudy transparent plastics

An excellent result, it looks like a new one!
__________________
Richard

Index:
recursive loop: see recursive loop
mole42uk is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 4:44 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.