Preventing amigas from getting yellow with time

[paulo_becas]

I was talking to my friend jVIDIA and we were wondering how can we protect our amigas from becoming yellow with time.
We need to protect them from UV and several doubts came up.
For example those amiga dust covers from Vesalia prevent that from happening? Are they light proof?
I would like to heard opinions about this matter from the guys here.

[Merlin]

It's quite simple. You need to seal oxygen away from the ABS plastic, as this is what is coupling to the brominated flame retardants in the plastic, making it go yellow.

It's all in here:- http://www.retr0bright.wikispaces.com

Clear coating the case with a satin-finish acrylic spray lacquer should do the job perfectly. No oxygen = no yellowing....

If you can get one with a UV filter chemical in it, so much the better.

[s2325]

Perfect is nerdy room - no oxygen, no light...

[paulo_becas]

Originally Posted by Merlin

It's quite simple. You need to seal oxygen away from the ABS plastic, as this is what is coupling to the brominated flame retardants in the plastic, making it go yellow.

It's all in here:- http://www.retr0bright.wikispaces.com

Clear coating the case with a satin-finish acrylic spray lacquer should do the job perfectly. No oxygen = no yellowing....

If you can get one with a UV filter chemical in it, so much the better.

Wow, now that's impressive, i'll give it a try later on, first i have to gather all the ingredients first.

[spannernick]

So that includes the keys too right,how about painting it the same colour is was before yellowing,does anyone know the name of the colour of the A500 and A1200.(well the A1200 is white..lol)

I was just thinking of the yellowing of the ABS plastic,It happens to white gloss paint too,it goes yellow in time.

[Arnie]

Paint it black, black is the new white



<------

[s2325]

"Color #0000 please."

[Sandro]

Originally Posted by Merlin

It's quite simple. You need to seal oxygen away from the ABS plastic, as this is what is coupling to the brominated flame retardants in the plastic, making it go yellow.

It's all in here:- http://www.retr0bright.wikispaces.com

Clear coating the case with a satin-finish acrylic spray lacquer should do the job perfectly. No oxygen = no yellowing....

If you can get one with a UV filter chemical in it, so much the better.

that is theory but not real life
acrylic spray (clear) doesn't work ,I tested it, my A1200 end up yellowed for the 3rd time
light and oxygen and cigarrete smoke : still penetrate
or the yellowing process is caused by the bad plastic (degrades itself)

this is my A1200 after bleaching 2 times ,the last one the spry acrylic process was included

[Predseda]

So: after you removed yellowing with peroxide, how long did it take the yellow plague to cover your Amiga again?

[demolition]

Originally Posted by Predseda

So: after you removed yellowing with peroxide, how long did it take the yellow plague to cover your Amiga again?

It starts yellowing immediately, but it can take from ½-2 years to become apparent again. The ones I did 2 years ago are still not as yellow as they were before I treated them. I used 3% peroxide so it was a weak solution. Although I don't have any merits to say so, it seems intuitive that the weaker solution with longer reaction time would reach a bit deeper into the plastic, making it last longer. A high concentration in a short time will only affect a very thin layer on top.

[Predseda]

And dont you have a feeling that the plastics became fragile then? The structure of the surface remained the same?

[demolition]

All the things I have treated does not seem any more or less fragile. It just changed color. The texture of the surface also feels the same.

[pandy71]

There are special cosmetics for cars to protect plastic parts against UV (and discoloration) - it should work well for Amiga also.

[demolition]

Originally Posted by pandy71

There are special cosmetics for cars to protect plastic parts against UV (and discoloration) - it should work well for Amiga also.

Sure, but then you'd have to use it when it is new and before it starts yellowing. It is too late if it has already yellowed, even if you retrobright it first.

[Sandro]

Originally Posted by demolition

Sure, but then you'd have to use it when it is new and before it starts yellowing. It is too late if it has already yellowed, even if you retrobright it first.

exactly
once the plastic is yellowed is over, you can do retrobright but the yellow plague will come faster because the plastic is weakened

this is like removing oxide to a piece of metal using sulfuric acid or phosphoric acid
the rust and oxide disappear fast but the oxide appears faster once you remove the piece of metal of the acid, the piece of metal end up weakened by the acid then enter in contact with oxygen,the oxide attacks faster

the problem is the lame plastic the Amiga computers were done: is unstable in the normal ambient ( atmosphere)

personally I do not bother anymore doing retrobright, my A1200 will remain yellowed forever

[Retrofan]

My first A1200 (bought around 5 years ago) had a LOT of yellowing. I retrobrighted it and yellow returned after a year and a half or so, but not so much. I retrobrighted it again after another year and a half, now it has passed maybe the same time but it's only a bit yellow...

I think I will have to retrobright it from now and then, maybe only every two years or more in a near future.

[demolition]

Originally Posted by Sandro

exactly
once the plastic is yellowed is over, you can do retrobright but the yellow plague will come faster because the plastic is weakened

I don't think that is why. The normal yellowing which takes years top happen, penetrates much deeper into the plastic since the molecules had time to move through it. When you retrobright, since it is done so fast, you only whiten a very thin top layer, and afterwards that top layer relatively quickly gets polluted again from what's underneath. Not because it is weakened.

[Sandro]

Originally Posted by demolition

I don't think that is why. The normal yellowing which takes years top happen, penetrates much deeper into the plastic since the molecules had time to move through it. When you retrobright, since it is done so fast, you only whiten a very thin top layer, and afterwards that top layer relatively quickly gets polluted again from what's underneath. Not because it is weakened.

ok I understand your theory
so according to this you must do retrobright for a month or so to make enough time the liquid penetrate deeper , so the yellowing process this tiime will be slower

anyways I still think that the plastic is unstable in the atmosphere so unless you use the Amiga in the outer space it will become yellowed again

[demolition]

Originally Posted by Sandro

ok I understand your theory
so according to this you must do retrobright for a month or so to make enough time the liquid penetrate deeper , so the yellowing process this tiime will be slower

anyways I still think that the plastic is unstable in the atmosphere so unless you use the Amiga in the outer space it will become yellowed again

I don't think the liquid penetrates the plastic - it is simply a medium supplying the oxygen molecules.
What I think is best is to use a weak retrobright solution to deyellow a piece, and keep doing it every year or so when it becomes too yellow again. The yellowing will be slower and slower for every time, but yes it will continue to yellow forever unless you seal it in a black box with nitrogen. If you want a one-shot solution, spray paint it, or find the moulds and cast some new ones without brominated flame retardants..

[pandy71]

Originally Posted by Sandro

exactly
once the plastic is yellowed is over, you can do retrobright but the yellow plague will come faster because the plastic is weakened

this is like removing oxide to a piece of metal using sulfuric acid or phosphoric acid
the rust and oxide disappear fast but the oxide appears faster once you remove the piece of metal of the acid, the piece of metal end up weakened by the acid then enter in contact with oxygen,the oxide attacks faster

the problem is the lame plastic the Amiga computers were done: is unstable in the normal ambient ( atmosphere)

personally I do not bother anymore doing retrobright, my A1200 will remain yellowed forever

Well... i strongly disagree - rust is oxide but removing it with proper solution instead rust you need to create passivisation layer (and generally all antirust protection focus on two things - remove weak layer of oxides as rust is to weak oxide to passivate metal and second create passivation layer stronger than rust) - ito works not only on iron alloys but same principle is on for example aluminum alloys - there is special process called passivation (usually electrolytic) on aluminum alloys.

As i understand main problem with yellowing of plastic is UV catalytic reaction with bromine in plastic - preventing UV to work is very important. Side to this such cosmetics create thin layer that works like fluid seal preventing plastic to react on air. Such layer can be permanent (ok semi) if painted with UV blocking transparent lacquer or temporary with some cosmetics (so from time to time you need to reapply it).

See how it looks in UV light - good movie to demonstrate sunscreen lotion in action: [ Show youtube player ]