Yellowing of the iMac

[tecneeq]

Yes, there is some yellowing in the first gen iMac already. I have three. One has a good picture, but yellowed case, another has a good case, but bad picture, so i swapped. Here is what i learned:

The case is made of two layers, the outer see-through layer, which is good plastic, not brittle, but has yellowed a bit. And the inner layer, which is some kind of beige plastic that got brittle and darkened considerably.

Both iMacs where bought at the same time and placed in the same classroom. One near the window, but not direct light, one in a darker corner.





So there you have it. Soon your iMac will look like a decaying tooth.

 

[tecneeq]

Another thing i noticed, the inner layer is like a dust magnet. The outer layer contains antistatic agents of some kind.

 

[RickNel]

Tooth-yellowing mostly caused by tea, coffee and tobacco smoke. Fortunately, most modern toothpastes contain a whitening agent.

I do not bother with de-yellowing any more than I would paint over a mediaeval chair. But for those who care, there is a vast online experience and correspondence in threads using the term "Retrobrite" or "Retrobright" (a TransAtlantic choice).

Plastics decay to brittleness is a much worse long-term threat to vintage computers. Protection from UV light is not enough, in the long run. I predict 3D printing of replacement plastic elements will become more significant in coming decades.

Rick

 

[Bunsen]

Also styled as "Retr0brite", with a zero, if one is searching.

 

[tecneeq]

The pros know it also as ,,Qwik-Brittle''.

Did i ever post the link to the article from the danish museum that took a deeper look into the chemistry of Retr0bright?

There it is: http://aktuelbevaring.natmus.dk/afrensning-af-plast-med-retrobright.html

They basically have looked into it and found it not a good solution.

 

[mcdermd]

retrobrite is easy to misuse in too high a concentration which results in "burning" or "blooming". But when done in an acceptable concentration, I think it does more good than harm, personally. I'm not seeing any surface chalkiness or difference in flexibility in the pieces I've done so I don't think I'm too worried about the brittleness they mention.

 

[Macdrone]

I see enough brittleness in non cleaned UV affected mac plastics I cant imagine it getting much worse much faster.