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Removing yellowing from plastics - Part 2

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On the contrary, I'm quite confident collectors prefer coins in shiny mint condition. While de-yellowing won't make a computer mint condition, it makes it look less ugly.

Though I understand your reasoning, this analogy doesn't quite work. Serious coin collectors will generally avoid cleaned coins at all costs (in fact, it's usually their biggest pet peeve about them). They want mint coins which are naturally clean.

I think this process of getting out the yellow on these old machines is absolutely awesome. But, truth be told, I'd prefer to do it myself on a machine I'm planning to buy, rather than someone having done it beforehand. A growing trend on eBay is to leave it up to the buyer to clean whatever collectable is being auctioned - you'll see this in descriptions all the time. Personally, I like this.

Now, an option for the seller to clean it for you at an additional cost? That'd work.
 
yellowing and prices

yellowing and prices

Now that a fairly quick, easy and cheap solution to yellowing has been found and is in the public domain, it's going to be interesting as to how this will affect prices for yellowed machines.

Yellowing wasn't necessarily a deterrent for me, but I know for people who bought computers for future retail value it certainly was. Unless it was a rarity, a yellowed computer was not as easy to sell as a non-yellowed one and prices reflected that.

Given that yellowing can now be eliminated with no apparent damage to the case will the price difference between yellowed and non-yellowed units close somewhat? Sure, there is still effort involved in de-yellowing, but it's not much effort and, if it's done properly, there is nothing to indicate it was ever yellowed in the first place!

There is still a question in my mind of whether repeat applications will remove ALL the yellow from a severly yellowed case, such as my RX-8800? Certainly my treatment didn't remove all yellowing from the RX-8800 (it did from the Vic-20) but that could simply be a matter of applying repeat treatments? Based on what I've seen so far I think it will remove it all, but I can't be conclusive about that just yet. Not until I have another crack at it.

Tez
 
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I've wondered about that too. In some of the most extreme cases I've seen, the yellowing is not just on the surface, but penetrates all the way through the plastic to the inside where 'the sun don't shine'. How does this process affect those pieces, and does it also affect the accompanying extreme brittleness of the plastic, or are those two separate issues?

--T
 
Are you sure antiques are sold in a "muddy" state because collectors want them like that, or rather because most people don't have the ability to carefully restore a painting without damaging it?

As for collector's value, in order to be worth any decent money most vintage computers are required to still have their original box and package material. Preferrably it should be in as-new condition too. Frankly those machines probably have been kept in their original box for 20 years and never suffered any yellowing unless the plastic detoriates while inside the box as well.

In any case, as long as nobody is trying to fool people, a bleached computer shouldn't do any damage. Often you can see wear on the keycaps, or at least check the feel if the computer has been used a lot or not. Of course on eBay you can not feel the item, but at least file a claim if you find out you were fooled. For that matter, people can grab a picture of a NOS item and instead send you a used one, in which you would instantly recognize you had been cheated.

By the way, cases that have been scratched or otherwise physically damaged won't heal by removing the yellowing. Often a cheese coloured machine has other defects that once carefully inspected it won't be so sought after anyway.
 
Even machines that have never been taken out of the box can yellow (some react with the plastic bag covering them over time (depends on the temp and humidity they are store in I would think). How many never opened Amigas has leaky batteries eating their guts out now?

Once this hobby progresses a bit you will have color charts and grading charts for every desireable system just like for cars and baseball cards. There will be pristine systems worth $1,000 and perfectly good systems 2 minor variations away from pristine worth $19.95 (that the owners feel is worth atleast $900). Heck I am sure somebody has a clear heavy duty shrinkwrap to encase computers so UV and dirty fingers never get near them again in the works.

As long as the units I like hold together and work I am happy.
 
Are you sure antiques are sold in a "muddy" state because collectors want them like that, or rather because most people don't have the ability to carefully restore a painting without damaging it?

Both can be true at the same time.

My feeling: don't mess around with my merchandise. I'll clean it.

As for collector's value, in order to be worth any decent money most vintage computers are required to still have their original box and package material.

Those machines tend to be pretty common, however; being boxed and in new/linke new condition is the only thing that makes them remarkable. Again, I can only speak for myself, but I have no interest in that stuff. I like rare equipment. A Lisa 1 doesn't need a box to sell for big $$.

In any case, as long as nobody is trying to fool people, a bleached computer shouldn't do any damage. Often you can see wear on the keycaps, or at least check the feel if the computer has been used a lot or not.

This is another thing: with the case clean, does the wear on other portions of the machine then make the overall wear look "uneven"?

Just Devi's Advocate here. Again, I love this de-yellowing. Very tempted to do it on my own stuff.
 
Of course a well used computer but with cleaned case will look "uneven". I'm thinking from a perspective that somebody would cheat on buyers, pretending a de-yellowed computer actually is a NOS one. Pretty much the opposite of someone trying to add discolouring and dents to newly manufactured furniture to make it look 200 years old.

Actually, currently I don't own a single piece of vintage computing that is badly yellowed. Perhaps one or two of my VIC-20's would like a bath, but I don't think they are anywhere near the cheesy yellow one sometimes can see. Currently I only own an Amiga 1200, which is another brand often bitten by the "yellow fever". One of my BBC Micros was a bit filthy but got much better already after scrubbing it with dish liquid. However one day I may be eager to try the process myself, just need to get something to motivate me.
 
Of course a well used computer but with cleaned case will look "uneven". I'm thinking from a perspective that somebody would cheat on buyers, pretending a de-yellowed computer actually is a NOS one. Pretty much the opposite of someone trying to add discolouring and dents to newly manufactured furniture to make it look 200 years old.

Hmm. Yes this whole subject of "collectability'' is an interesting one and what adds value and what does not seems to be really subjective.

For example, let's say I bought a de-yellowed case that looked as fresh as the original and had no damage at all from the de-yellowing process, but I didn't know it had been de-yellowed. It wouldn't worry me if I found out later that it had been de-yellowed. I certainly wouldn't feel I had been cheated by the seller.

But then..I would not be buying for the sake of collectability and investment. There is a different mindset I guess, and there are lots of esoteric arguments as to what count's towards "authenticity" regarding these items. I guess that is why there are "color charts and grading charts for every desireable system just like for cars and baseball cards." to cite Unknown_K?

If I was trying to sell one of my de-yellowed items (say the Vic-20) on e-bay or our local Trade-me I would probably just say "restored to near-original condition" and accompany it with plenty of pictures. Going into the details of peroxide pastes, rubber gloves and foaming mixtures might scare a few people off :) . People could ask me, if they wanted more details.

But then, is this even going too far? That same Vic 20 was repaired by me, and includes 6 chip replacements, with one of these chips being from a Terry Yager-supplied motherboard, which itself was an earlier Vic-20 version. I'm not even sure the motherboard presently in the Vic-20 came with the case in the first place.

Do I need to mention all of these things, to be totally honest to the buyer?

Can you see the point I'm making here? To the purist collectors out there, all these things might matter. But where do you draw the line? Most people don't even KNOW the history of their 2nd hand machines.

Actually, in the end, whether you mention those details above or not probably doesn't matter. As was mentioned before, The REAL purist to whom these things are important, will only ever buy a system in a sealed box that has never been opened or touched. It will be guaranteed free from exposure to rubber gloves and foam, Terry Yegar's used chips and Tezza's barely-adequate soldering attempts :) .

It may not actually work (in fact they will never know), but for such collectors, that is not the point.

Tez
 
I think the distinction that needs to be made here is the difference between some kind of collector and an antiquarian. Collectors could theoretically collect anything from "as is" to "unopened" to "restored", as well as historically correct antiques. It is the antiquarian and museum archivist who has specific needs which will likely preclude much of what is otherwise collectible.

I notice that the automobile world is full of restored vintage vehicles which are quite acceptable to them, even though those would not be true antiques because of the multitude of replaced parts (such as paint) which are not in themselves vintage or original. This would not be acceptable to an antiquarian although he may have to accept it in lieu of something better.

An example where a full restoration is definitely not acceptable is in antique furniture. Historically correct repairs (with the correct glue etc) is OK but refinishing destroys the item and makes it almost worthless. An even worse situation is in old violins. I've seen a lot of fine instruments repaired by "wood workers" who know not what they do, resulting in an instrument significantly lower in value and which will forever remain so because their work cannot be reversed. Much history is destroyed by people who mean well.

When it comes to the computer restorations which are talked about here I think it is in the same category as restored automobiles. These are working machines and a working repair which could have been done at the time of the computers heyday is just fine. The de-yellowing seems to me as just a refurbishing procedure which is not all that different from a good cleaning.

Someone who has special requirements for their collection will (or should) know what it is they want or don't want. The serious antiquarian may not want a de-yellowed machine but will also know how to avoid any such thing. In short, I don't think there is anything wrong with selling a "restored" computer, as talked about here, without providing any specifics.
 
Just for the record, all else being equal, a car with an old, sun-faded original paint job is usually more desirable to a collector than the same car with a shiny fresh re-paint.

Back to computers, for myself, a somewhat yellowed, shightly battered machine with original software & docs is more desirable than a similar machine in the box, but minus S&D, FWIW.

As for museums, they are usually big on restoring antiques, using proper, professional methods. Those methods have been worked out in much the same way as the de-yellowing process, by experts trying different ways of doing things till they got it right. And who knows, this process may not be fully evolved yet either. Someone else may figure out a better way, based on prior research that's been started here.

--T
 
Years ago I read about how old vintage race cars were repainted with a paint that cracked after it dried to look just like an original paint job that cracked over time. The car was one of those small green race cars where the thin wire wheels stuck out the sides if you know what I mean.

Anyway if the computer is worth enough mint, people WILL find a way to fake it. Same with individual parts (don't plenty of chinese sellers sell fake old CPUs and other chips already?).
 
Years ago I read about how old vintage race cars were repainted with a paint that cracked after it dried to look just like an original paint job that cracked over time. The car was one of those small green race cars where the thin wire wheels stuck out the sides if you know what I mean.

The risk you take in collecting anything is fakes and forgeries, I was kicked off EBAY many years ago cause I got into a spat with some guy selling mint stamps, his stamps were well below value, when I brought up the suspicion of reminted or fakes, he flipped his girly wig.. :eek:
 
@ Terry Yager

The science behind this process is actually quite sound and is using the same free radical process that originally formed the yellowing.

There may be more than one way to do this with a cocktail of chemicals, however, the basic underlying principle will still be the same.

I would be quite interested to see if anyone does come up with another way to skin this particular cat; it will still involve UV light though, as the vibration of bromine molecules when exposed to UV light is a unique feature that we are exploiting to destabilise them and remove the oxygen from them.

The problem I've had is that I've not found another chemist with enough of an interest to kick the ideas around with, and I don't have the time to play with lots of different experiments.

@ Tezza

You may get patchiness on large surfaces as it is an unfortunate feature of large surface plastic mouldings, where the masterbatch plastic may not flow uniformly around the mould or where there were temperature differentials inside the mould. A second treatment should make it less noticeable.

It could also be due to differences in how the flame retardent migrates through the plastic, as temperature differentials may cause differences in the crystalline structure of the plastic as it cools, a bit like alloying in steel, where you can get autensic and martensic structures within the same piece of metal and different properties result.

@ Unknown_K

Spot on; it's exposure to oxygen that causes the yellowing, although UV light can accelerate it. Items that have been boxed and in the dark for years can still yellow without exposure to light.

@ All

I can honestly say that once we had worked out how to do this, I never expected the reaction and support that has come from so many different retro groups on this subject, it's been phenomenal. I took this on as I enjoy challenges in chemistry and the word 'impossible' just means that someone hasn't cracked it yet. Projects like this bring out the research chemist and alchemist inside me that's still there, even though I've not put on a white coat for over eleven years.

It's also a good bit of useful science abuse and a poke in the eye for the skeptics that said it couldn't be done, a bit like proving the Earth isn't flat after all! :mrgreen:
 
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A Noble prize, maybe not but good on you Merlin. You, or whatever team of people figured out the basic chemistry of plastic yellowing and what should reverse it has/have made a significant contribution to this hobby.

Tez
 
A Noble prize, maybe not but good on you Merlin. You, or whatever team of people figured out the basic chemistry of plastic yellowing and what should reverse it has/have made a significant contribution to this hobby.

Tez

The interesting thing about this thread, I spent some time on many web pages looking for some thing or someone who had any ideas on how to de-yellow plastic, I found nothing, until I came to this web site.

:0
 
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As I said earlier in one of these threads, to clean or not to clean, that is the question.

Some want their machine to gracefully age like the owner, others want the pure nostalgia of seeing the machine in the same condition as when they opened the box years ago. It comes down to personal preference and there is no 'right' answer to this, it's down to what the owner wants to do.
 
This post is great information. I found it while searching for info on removing yellowing from back lit sign material (its either Lexan or SGA, not sure which)
Customer didn't to pay for it tho, so I wasn't able to test it and see if it works.

Any one ever try this kind of process on any materials like that??
 
It should work on most types of thermoplastics, Lexan , Perspex etc. included, since they still add flame retardants to comply with things like lighting regulations, so that a hot bulb doesn't make it burn the place down.

@ Gerry

There are a couple of threads on English Amiga Board (easily Googled) about this process as well; we split things across a number of retro sites, although here and EAB are the main sites that have been carrying out the development.

We nicknamed the process "Retr0-Brite" because of this...:mrgreen:

It's a shame it can't be patented though....mind you, if anyone tries now, these threads constitute prior art.
 
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