Retr0bright on it's own is not a permanent solution - here's why...

Merlin

Ministry of Retr0bright and Street Judge
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Hi,

Sometimes I get e-mails from people that complain that their Retr0brighted parts have gone yellow again over time. Rather than put this in the support thread where it may get lost over time, I thought that if I made it a separate sticky, it may get noticed more.

So, why do the parts go yellow again? It's for a couple of reasons. I shall explain below.

Firstly, I stated in the Wiki that the chemical reaction is reversible; that's why we are able to reverse the yellowing that has occurred over time. The downside of this is that it can also revert back, as it's reversible and can go in either direction.

The second reason is that Retr0bright only treats the surface, it can't penetrate into the plastic where more of the fire retardant is present. Unfortunately, the fire retardant can migrate through the plastic and this is another reason that yellowing can occur again, as more migrates to the surface.

Is there anything that can be done about this? YES, and it's the part of the treatment that most people seem to forget.

Just as the Triangle of Fire needs fuel, oxygen and a source of ignition, the yellowing of the plastics needs three things; The flame retardant, UV light and oxygen - the oxygen is in the air we breathe. Take the oxygen away from both triangles and you don't get a fire and you don't get yellowing, either. How can you do this?

The answer is quite simple. Once the parts have been treated, you should coat the parts in a coat of clear, satin finish acrylic lacquer. This has the effect of cutting off the oxygen supply to the fire retardant and will prevent further yellowing.

For added insurance, you should use an acrylic lacquer that includes a 'UV Blocker' or 'UV Filter'. These products contain a chemical called an 'up-converter', a chemical that has the neat ability to take light in at one wavelength and give it out at another completely different wavelength, in a similar way that fluorescent colours need UV light to make them 'glow'. By shifting the wavelength of the UV light via an up-converter you effectively 'turn off' the UV light, that stops the bromine molecules from vibrating and gaining enough energy to drive the yellowing reaction.

Up-converters are used quite widely in plastics these days for this very reason, however, they weren't used in the master batches back when our machines were built and by using a lacquer containing an up-converter, you are retro fitting the answer to the problem.

This is about as close as you will ever get to a permanent fix for the yellowing problem and I hope that it helps those people who have been disappointed to find that their cherished parts have started to discolour again.
 
Or get a mancave without any windows and the problem is solved. Isn't that how a mancave is supposed to be anyway? :)
 
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Or get a mancave without any windows and the problem is solved. Isn't that how a mancave is supposed to be anyway? :)

"I'm in a mancave and Windows wasn't my idea.." :rofl3
 
A question.
When i have tried to coat plastic parts i have always used a plastic primer before to get the clearcoat to stick to the plastic.

Is this needed or have you found some sort of special plastic clearcoat?
 
You shouldn't need a primer, Kawazu.

The solvents in the acrylics are a mix of low boiling point and high boiling point solvents. The low boilers just get the lacquer to the surface then the flash off, leaving the high boiling solvents (usually aromatic ones) to coalesce the lacquer film and ensure an even coat.

These high boilers also 'etch' and denature the surface of the plastic very slightly and this is what creates the bond between the lacquer and the plastic. It effectively 'welds' itself on.
 
Ok.
The experience i have with coating plastic is that if you dont use a plastic primer the clear coat will not stick proparly but its worth a try :)

My old A500 will go first so i dont mess upp my 3000 :p
 
Wouldn't clear-coat give the plastics a gloss finish thus losing the original texture?
 
So what is this clear coat you're talking about? Is it a can of spray paint? Or, is it a regular can of paint and then you need a paint brush.. Are there any brands that are recommended?
 
Hmm... There's a brand called Tru Vue that blocks >97% of UV light. Another brand that has a UV blocker is Krylon UV-Resistant Clear. Blick UV Protect is yet another brand.

A lot of auto acrylic spray lacquers also have UV up-converters in them, so check your local auto parts superstore.

Typing "acrylic spray lacquer" and "UV filter" into your search engine of choice should find something suitable locally.
 
Is the halfords satin lacquer uv resistant? The normal lacquer is, but theres no mention for the satin one.

The halfords stuff is only made up the road from me as well after looking at the safety precautions sheet.
 
@ sneeker

I take it that you are near Bury or Middleton then, he said with a wink...;)

A couple of goodly coats of satin lacquer should do it, even if it has no UV blocker, as it will cut the oxygen off from the ABS.
 
Yeah, i had my A4000 retrobrighted by Cosmos less than 18 months ago and it is now yellow again.
I think the best way is to paint it.
 
the more yellowed I own (amiga500plus and cbm1571) where stored during 15 years with their boxes in a closet and "never" seen the sun...:blink:

on the other hand my A4000D never yellowed at all :cool:

plastics are certainly different during different production phase ...?
 
ABS is a polymer and is a bit like DNA, in that no two masterbatches of plastic are ever exactly alike. The amount of flame retardant added would also have varied from batch to batch and some might not have had any in at all, depending on the quality control.
 
Have you ever seen a yellow A2000?
It seems only the A2000 plastic never change: military spec!!!:)
 
My old 2000 had a metal shell, and the front plastics were that weird brown/grey that Amiga's seem to be.
 
Merlin - Im in Oldham - Its made on salmon fields on the way to shaw, on the halfords site you can read the safety sheet and it lists their address :)
 
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