Discoloured clear plastic tuning scales. - UK Vintage Radio Repair and Restoration Discussion Forum

Neil Purling · 11th Jun 2011, 9:12 am

This is not about any equipment I own.
However..... I would like to know if there is a solution for clear dials that have gone a dark brown/orange colour?
I do not know if this is due to chemical action in inferior materials or by exposure to light.
I appreciate that a cosmetic defect like this would be serious and might put off potential buyers of something. I thought that if there was a solution I could get a bargain.

HamishBoxer · 11th Jun 2011, 1:24 pm

I have a nasty feeling they don't clean, but hope I am wrong.

David

wireful3 · 11th Jun 2011, 1:39 pm

I think you are right David. I was told it is caused by the action of light on the material and this could not be reversed.

Skywave · 11th Jun 2011, 2:35 pm

I've always believed that this was due to a slow & permanent chemical reaction beween the polymer of the material and ultra-violet in sunlight. Hence, the result is non-reversible.

Al.

neon indicator · 11th Jun 2011, 3:09 pm

It may be reversible...

http://retr0bright.wikispaces.com/

Another success on "yellowed" Lego

Quote:

I use "Vanish Power O2". Works great and also whitens discolored white bricks (improves the yellowing effect but I've not experimented to see if a longer soak will restore the color even better). I usually leave bricks in for an hour, rinse, dry and they look great.

Maybe some Toothpastes (will remove scratches and make surface Matt if rubbed though!)

See this Lego thread http://www.eurobricks.com/forum/inde...pic=21898&st=0

Quote:

LEGO fans have discussed this problem for years, even concluding (correctly) that ultraviolet light can contribute to faster yellowing of colors like white, blue, and old light gray (some of the key colors of Classic Space sets). Fans like sugegasa have experimented with the effects of sunlight on the new grays, but nobody could quite figure out how to reverse the effect on older, yellowed bricks.

http://www.brothers-brick.com/2009/0...look-new-news/

Also sometimes "yellowing" is due to a smoker. Good old Soap (or Detergent) and Water will eventually take off the cigarette smoke deposits.

Neil Purling · 11th Jun 2011, 9:46 pm

On the article I saw it isn't down to cigarettes, the case itself being cream bakelite/Urea Formaldehyde that is of normal tint.
It would be interesting to see the effect of the product mentioned above on some scrap articles of clear material that are discoloured. That is, if anyone has tried it yet.

paulsherwin · 11th Jun 2011, 11:27 pm

Vanish Power O2 is basically hydrogen peroxide. I'd be surprised if it could reverse changes made by UV but it would certainly help with contaminants such as cigarette tar which have leached into the surface. It might also be worth trying normal household bleach which is more aggressive than HP used alone.

neon indicator · 12th Jun 2011, 11:31 am

Milton (a sodium hypochlorite based bleach) only makes a slight improvement on yellowed Lego bricks. But we have not tried the other Lego cleaning solutions listed. So the "kind" of bleach and the "kind" of plastic may be significant to any results.

ABS seems to go particularly discoloured. I've had some success with Ajax cream on old plastic cases (it's abrasive so not suitable for clear panels or high gloss finish).

Also don't mix cleaning agents. Some mixes will result in near explosive release of Chlorine gas

i.e. sodium hypochlorite calcium hypochlorite or related based bleach really bad to mix with ANYTHING. Mixing it with anything acidic is bad, mixing with Ammonia based items seriously bad. Mixing it with Hydrogen Peroxide "sounds" harmless as the result is salt, water and oxygen... In theory. But it's an extremely explosive reaction and pure oxygen is explosive on anything even just embers.

ftp://ftp.dep.state.fl.us/pub/water_...ompatChart.pdf

http://en.wikipedia.org/wiki/Sodium_hypochlorite

WME_bill · 14th Jun 2011, 8:39 pm

Mixing Harpic (a solid acid) with Bleach (sodium hypochlorite) was a nice schoolboy prank, many many years ago. It released some chlorine gas which made people cough. An alternative to Hydrogen Sulphide, bad eggs sme ll.But thats another tale.
Many of the solid plastics like ABS, PVC and HD Polythene contain plastisers, which make the material perish under Ultra Violet sunlight, so the changes may not be reversible. A gentle rubbing down of the surface (3M Wet and Dry paper, with lots of water, as used after car spraying) may well be the best. For clear perspex, you can rub down, using progressively finer grades of grit, as was done to remove scratches on Spitfire/Hurricane windscreens in 1940. But it is a cruel task, and getting small quantities of 600 or 1200 grit difficult. Try the stone polisher or geologist slide makers on the web. Brasso (alkaline) or Silvo (acid) metal polishes can also be used. I used Brasso once on a stained binocular lens, and it improved it quite a bit. Toothpaste: would the peppermint in toothpaste linger on in the material I wonder, though there is also a bleach. Bill m0wpn

11th Jun 2011, 9:12 am	#1
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Discoloured clear plastic tuning scales. This is not about any equipment I own. However..... I would like to know if there is a solution for clear dials that have gone a dark brown/orange colour? I do not know if this is due to chemical action in inferior materials or by exposure to light. I appreciate that a cosmetic defect like this would be serious and might put off potential buyers of something. I thought that if there was a solution I could get a bargain.

11th Jun 2011, 1:24 pm	#2
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: Discoloured clear plastic tuning scales. I have a nasty feeling they don't clean, but hope I am wrong. David

11th Jun 2011, 1:39 pm	#3
wireful3 Retired Dormant Member Join Date: Sep 2003 Location: Bristol, UK. Posts: 808	Re: Discoloured clear plastic tuning scales. I think you are right David. I was told it is caused by the action of light on the material and this could not be reversed.

11th Jun 2011, 2:35 pm	#4
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Discoloured clear plastic tuning scales. I've always believed that this was due to a slow & permanent chemical reaction beween the polymer of the material and ultra-violet in sunlight. Hence, the result is non-reversible. Al.

11th Jun 2011, 9:46 pm	#6
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Re: Discoloured clear plastic tuning scales. On the article I saw it isn't down to cigarettes, the case itself being cream bakelite/Urea Formaldehyde that is of normal tint. It would be interesting to see the effect of the product mentioned above on some scrap articles of clear material that are discoloured. That is, if anyone has tried it yet.

11th Jun 2011, 11:27 pm	#7
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Discoloured clear plastic tuning scales. Vanish Power O2 is basically hydrogen peroxide. I'd be surprised if it could reverse changes made by UV but it would certainly help with contaminants such as cigarette tar which have leached into the surface. It might also be worth trying normal household bleach which is more aggressive than HP used alone.

12th Jun 2011, 11:31 am	#8
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: Discoloured clear plastic tuning scales. Milton (a sodium hypochlorite based bleach) only makes a slight improvement on yellowed Lego bricks. But we have not tried the other Lego cleaning solutions listed. So the "kind" of bleach and the "kind" of plastic may be significant to any results. ABS seems to go particularly discoloured. I've had some success with Ajax cream on old plastic cases (it's abrasive so not suitable for clear panels or high gloss finish). Also don't mix cleaning agents. Some mixes will result in near explosive release of Chlorine gas i.e. sodium hypochlorite calcium hypochlorite or related based bleach really bad to mix with ANYTHING. Mixing it with anything acidic is bad, mixing with Ammonia based items seriously bad. Mixing it with Hydrogen Peroxide "sounds" harmless as the result is salt, water and oxygen... In theory. But it's an extremely explosive reaction and pure oxygen is explosive on anything even just embers. ftp://ftp.dep.state.fl.us/pub/water_...ompatChart.pdf http://en.wikipedia.org/wiki/Sodium_hypochlorite Last edited by neon indicator; 12th Jun 2011 at 11:46 am.

14th Jun 2011, 8:39 pm	#9
WME_bill Octode Join Date: Oct 2007 Location: Exeter, Devon, UK. Posts: 1,554	Re: Discoloured clear plastic tuning scales. Mixing Harpic (a solid acid) with Bleach (sodium hypochlorite) was a nice schoolboy prank, many many years ago. It released some chlorine gas which made people cough. An alternative to Hydrogen Sulphide, bad eggs sme ll.But thats another tale. Many of the solid plastics like ABS, PVC and HD Polythene contain plastisers, which make the material perish under Ultra Violet sunlight, so the changes may not be reversible. A gentle rubbing down of the surface (3M Wet and Dry paper, with lots of water, as used after car spraying) may well be the best. For clear perspex, you can rub down, using progressively finer grades of grit, as was done to remove scratches on Spitfire/Hurricane windscreens in 1940. But it is a cruel task, and getting small quantities of 600 or 1200 grit difficult. Try the stone polisher or geologist slide makers on the web. Brasso (alkaline) or Silvo (acid) metal polishes can also be used. I used Brasso once on a stained binocular lens, and it improved it quite a bit. Toothpaste: would the peppermint in toothpaste linger on in the material I wonder, though there is also a bleach. Bill m0wpn