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

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    Ministry of Retr0bright and Street Judge VIP
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    Default Retr0bright on it's own is not a permanent solution - here's why...

    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.
    The future's so Retr0bright, I gotta wear shades.....

    As rkauer said:-
    "Retro computers seems like an orgasm: it is always better to have a real one than fake it".

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    :Commodore: vc20/c64/c64c/sx64/c128/c128d/c128dcr/c16/c+4/dtv
    :rainbow: a500/a500+/CDTV/ a600/a1000/a1200/a2000/a2500/a3000/a4000D/A4000T
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    Great explanation.

    Bryce.

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    Amibayer! demolition's Avatar
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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?
    A1200 (NOS) : 030 33MHz 128MB fast RAM (ACA1232) : Indivision AGA MkII : 8GB CF : RR USB : Ethernet
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    : Ethernet | A600 #2 : 010 : 2MB chip
    A500 : 68000 42MHz : 1MB chip : 8MB fast : 4GB CF | A500+ : 080 V2+ : 128MB fast : 2MB chip : 32GB CF

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    Quote Originally Posted by demolition View Post
    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.."
    The future's so Retr0bright, I gotta wear shades.....

    As rkauer said:-
    "Retro computers seems like an orgasm: it is always better to have a real one than fake it".

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    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?
    | Amiga 3000T | CSMK II @ 100mhz | Prometheus | Voodoo 3 | rtl8029 nic | VarIO | Delfina | FastATA4000

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    Ministry of Retr0bright and Street Judge VIP
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    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.
    The future's so Retr0bright, I gotta wear shades.....

    As rkauer said:-
    "Retro computers seems like an orgasm: it is always better to have a real one than fake it".

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    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
    | Amiga 3000T | CSMK II @ 100mhz | Prometheus | Voodoo 3 | rtl8029 nic | VarIO | Delfina | FastATA4000

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    Wouldn't clear-coat give the plastics a gloss finish thus losing the original texture?

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    Quote Originally Posted by tokyoracer View Post
    Wouldn't clear-coat give the plastics a gloss finish thus losing the original texture?
    Use satin finish acrylic lacquer as per original post.

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