carlsson
Veteran Member
On the Apple IIe, did you bleach all the keys or only those badly discoloured? Now it looks like those few keys are significantly lighter grey than the others, as well as slightly more shiny.
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Removing yellowing from plastics - Part 2
- Thread starter Merlin
- Start date
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tezza
Veteran Member
All the keys were processed. However, the more badly affected ones got a day longer, as they had not completely de-yellowed/de-greened at the end of two days. They are a little lighter. Also their decolourisation was not as consistent. In particular the two Shift keys are somewhat streaky. The streakiness was evident at the end of two days, when they still held a some green colour. I was hoping the streakiness would disappear with a day more, but actually it got worse (but the green did disappear).
The photo of the Apples were taken under flash, and there is also a side light on the processed one. The flash is harsh, in that if there are any imprefections it will show them. The lightening/streaking of the worst affected keys is not so noticable in normal light. However it can be distinguished if you look closely.
I'll be writing a blog about treating keys when I get some time. What I've found with both with the Atari and the Apple is that decolourising keys by immersing them in an activated solution is not as risk-free as painting cases with a paste. While the keys certainly look better than they did, letter fade (with the Atari) and bleaching/streaking (with the Apple) both occurred.
Tez
The photo of the Apples were taken under flash, and there is also a side light on the processed one. The flash is harsh, in that if there are any imprefections it will show them. The lightening/streaking of the worst affected keys is not so noticable in normal light. However it can be distinguished if you look closely.
I'll be writing a blog about treating keys when I get some time. What I've found with both with the Atari and the Apple is that decolourising keys by immersing them in an activated solution is not as risk-free as painting cases with a paste. While the keys certainly look better than they did, letter fade (with the Atari) and bleaching/streaking (with the Apple) both occurred.
Tez
Last edited:
Lorne
Veteran Member
When I processed keyboard keys, I gave them a stir about every 30 minutes. That would get the bubbles off, mix up the solution, and turn the keys over (I wasn't sticking them down with anything). It took mine about a half a day in the heat/sun.
Are you putting them in and leaving them alone, or are you giving them a stir every once in awhile?
The keys are probably mixed up in the factory from many batches so they are not all the same with respect to plastic and UV mix. I would expect the shades to be different kind of like the many amiga keyboards I have seen where the spacebar is yellowed and the other keys are fine.
tezza
Veteran Member
Not really a stir but I did tend to prod and poke them every hour or so. Some would have so many bubbles on them they would float to the surface, despite the ballast. This could partly explain the streakiness on a few.
Tez
tezza
Veteran Member
Yes, I have a Commodre executive just like that. I've removed the spacebar and will be de-yellowing it this weekend.
Tez
Merlin
Experienced Member
Guys,
I finally got around to writing The Retr0brite Project up; I've sent it to my friend Zetr0 over at English Amiga Board, who is going to add some bells and whistles and put it all on a web page. Once that's all done, I'll post the link here. The draft with the pictures is too big to post here and besides, it's not complete.
My next task is to write the articles on how to make the gel mixture up and apply it, so that it's all laid out and a goof-proof as we can make it.
I have included thanks to all of you who have contributed to this project and I hope that you are OK with me using some of the pictures.
:D
I finally got around to writing The Retr0brite Project up; I've sent it to my friend Zetr0 over at English Amiga Board, who is going to add some bells and whistles and put it all on a web page. Once that's all done, I'll post the link here. The draft with the pictures is too big to post here and besides, it's not complete.
My next task is to write the articles on how to make the gel mixture up and apply it, so that it's all laid out and a goof-proof as we can make it.
I have included thanks to all of you who have contributed to this project and I hope that you are OK with me using some of the pictures.
:D
Terry Yager
Veteran Member
Merlin
Experienced Member
That should be OK, Terry; it will also be going on a Wiki at ClassicAmiga.
I'll be in touch once it's sorted.
I'll be in touch once it's sorted.
Merlin
Experienced Member
@ Lorne / Tezza
Get this!! Our Retr0brite process has been validated by another very experienced chemist (harpo) over at Atari Age!!
This is what he wrote:
--------------------------------------------------------------------------
OK,
I will chime in here. Professionally, I have BS and MS degrees in chemistry and worked with polymers (plastics and such) for many years. I have not tried this protocol on my own cases that are yellowed yet, because I am just getting back into my old system while teaching my son some computer programming skills (what a great system for teaching programming ).
IMHO, the chemistry that is presented is valid for the mechanism of the "ageing/yellowing" phenomenon and how to reverse it.
When using the materials described be aware that if you don't follow the protocol TO THE LETTER you are out on your own and working with some potent chemical materials and can not be certain of the results you will obtain. I will reiterate what others have said, concentrated hydrogen peroxide is an EXTREMELY powerful oxidizing agent and can cause burns to the skin (I know from first hand experience), explosions when mixed with reducing agents (think rocket fuel), or damage to other materials it comes in contact with.
The 2% hydrogen peroxide you get at the pharmacy is not concentrated enough to accomplish this reaction. You need to use concentrations in the 12-15% range. You can start with the peroxide available at a beauty supply for bleaching hair but be careful to dilute it properly. If you do not know how to calculate the dilution ask for help! And "if a little is good, more must be better" DOES NOT apply here. The purpose of the TAED from the Oxy is to act as a catalyst. A catalyst is an agent in a chemical reaction that reduces the energy required to get the reaction going. You want the catalyst to be "pushing" the reaction, not excess concentration of the peroxide. That is the beauty of the protocol developed. If you use the concentrations and the materials described you should get undetectable amounts of oxidation of the base polymer and only reaction with the bromine compounds. The other thing to remember is that the UV is VERY important. The UV breaks the weak bonds in the peroxide causing the formation of the active radicals. If you have an old "Black Light" pull it out and use it. Otherwise wait until you have a nice sunny day. And as soon as the yellowing is observed to be gone, remove the piece and rinse it thoroughly to get rid of all traces of the TAED and OXY.
My feeling is that those individuals who have observed degradation and roughening of the surface of their plastic cases probably used too high a concentration of peroxide. If you stay on the dilute side and use the catalyst and UV so that only reaction with the bromine is favored, you should get an outstanding result.
As far as slowing the recurrence of the yellowing, I would suggest using a very light coating of ArmorAll or other surface protectant. It will slow the absorption of oxygen onto the surface and also reduce the amount of UV penetration slightly. It will have that slippery overly shiny feel and appearance that all surface protectants leave, but it will work to slow the recurrence of this phenomenon if that is foremost to you.
--------------------------------------------------------------------------
That's all I need to prove that we have got it absolutely right in the way we are going about it. I am absolutely made up, as I was looking for someone impartial to validate my chemistry reasoning all along.
Result!!!! Well done guys!!
:mrgreen:
Get this!! Our Retr0brite process has been validated by another very experienced chemist (harpo) over at Atari Age!!
This is what he wrote:
--------------------------------------------------------------------------
OK,
I will chime in here. Professionally, I have BS and MS degrees in chemistry and worked with polymers (plastics and such) for many years. I have not tried this protocol on my own cases that are yellowed yet, because I am just getting back into my old system while teaching my son some computer programming skills (what a great system for teaching programming ).
IMHO, the chemistry that is presented is valid for the mechanism of the "ageing/yellowing" phenomenon and how to reverse it.
When using the materials described be aware that if you don't follow the protocol TO THE LETTER you are out on your own and working with some potent chemical materials and can not be certain of the results you will obtain. I will reiterate what others have said, concentrated hydrogen peroxide is an EXTREMELY powerful oxidizing agent and can cause burns to the skin (I know from first hand experience), explosions when mixed with reducing agents (think rocket fuel), or damage to other materials it comes in contact with.
The 2% hydrogen peroxide you get at the pharmacy is not concentrated enough to accomplish this reaction. You need to use concentrations in the 12-15% range. You can start with the peroxide available at a beauty supply for bleaching hair but be careful to dilute it properly. If you do not know how to calculate the dilution ask for help! And "if a little is good, more must be better" DOES NOT apply here. The purpose of the TAED from the Oxy is to act as a catalyst. A catalyst is an agent in a chemical reaction that reduces the energy required to get the reaction going. You want the catalyst to be "pushing" the reaction, not excess concentration of the peroxide. That is the beauty of the protocol developed. If you use the concentrations and the materials described you should get undetectable amounts of oxidation of the base polymer and only reaction with the bromine compounds. The other thing to remember is that the UV is VERY important. The UV breaks the weak bonds in the peroxide causing the formation of the active radicals. If you have an old "Black Light" pull it out and use it. Otherwise wait until you have a nice sunny day. And as soon as the yellowing is observed to be gone, remove the piece and rinse it thoroughly to get rid of all traces of the TAED and OXY.
My feeling is that those individuals who have observed degradation and roughening of the surface of their plastic cases probably used too high a concentration of peroxide. If you stay on the dilute side and use the catalyst and UV so that only reaction with the bromine is favored, you should get an outstanding result.
As far as slowing the recurrence of the yellowing, I would suggest using a very light coating of ArmorAll or other surface protectant. It will slow the absorption of oxygen onto the surface and also reduce the amount of UV penetration slightly. It will have that slippery overly shiny feel and appearance that all surface protectants leave, but it will work to slow the recurrence of this phenomenon if that is foremost to you.
--------------------------------------------------------------------------
That's all I need to prove that we have got it absolutely right in the way we are going about it. I am absolutely made up, as I was looking for someone impartial to validate my chemistry reasoning all along.
Result!!!! Well done guys!!
:mrgreen:
carlsson
Veteran Member
It is very good to have this pointed out. I've read the opinion from quite a number of people assured it is the heat, not the light that causes a reaction. While placing items in the sunlight, it would be easy to mistake one for the other. However when using an UV lamp, it becomes obvious it doesn't generate much heat.harpo said:
Merlin
Experienced Member
@ Carlsson
I've maintained this about the UV light all along; it's others that thought that the heat was helping when really it isn't.
I've maintained this about the UV light all along; it's others that thought that the heat was helping when really it isn't.
Lorne
Veteran Member
Merlin
Experienced Member
He was able to follow my chemistry reasoning and validate that we were correct about the bromine free radical theory.
It's nice when someone proves you right, especially as that guy is way more qualified than I am, although what I lack in qualifications I make up for in experience.
Here's what I posted at Atari Age that prompted the response I posted earlier.
--------------------------------------------------------------------------
I am the alchemist who has been writing all of these articles about de-yellowing plastic. This is my first post on here and it's bound to be controversial....
OK, let's lay this out once and for all as simply as I can. Whilst I am aware that acetal butadiene styrene (ABS) can oxidise under light to form the hydroperoxide as others have alluded to on here, here is one thing that you may not be aware of from the threads, as I am still trying to write this process up for a Wiki, but people keep asking me damn fool questions about it
The process ONLY works in the presence of UV light or sunlight; now, that may not seem like a big thing, but the only molecules in the finished plastic that react so quickly to UV light are Bromine molecules from the Poly Brominated Diphenyl Ethers (PDBEs) in the flame retardant. If you try the experiment in the dark with the same chemicals, the parts don't change colour and just get wet. If this wasn't down to Bromine chemistry in the flame retardant, the polymer would react in any conditions, even in the dark; clearly it doesn't.
The only scientific explanation that fits what we are seeing here is the reaction of Bromine under UV light conditions. Bromine has a single electron spare in it's outer p-shell (Does anyone remember electron shells?). Bromine is 1s2 2s2 2p6 3s2 4s2 3d10 4p5 hence the negative charge of a Bromine radical as it would prefer an even number of electrons. By neutralising it with a single hydrogen created by the catalysis of hydrogen peroxide by tetra acetyl ethylene diamine (TAED) we allow the Bromine to be reduced by the electron and it goes to a stable 4p4 in the outer p-shell.
The key is to use the optimum strength of hydrogen peroxide, which is around 10 to 15%. The white "bloom" you may see is down to peracetic acid which is one of the breakdown products of TAED and this is also a powerful bleach in it's own right. Too strong a solution and it does seem to etch the surface, which is probably the peracetic acid attacking the hydroperoxide of the oxidised polymer as well as working on the bromine molecules.
Now, anyone can feel free to troll this explanation, but after having put months of work and research into this, at least back your argument up with some sort of scientific critique. I am achemist with 25 year's experience and although I may not have a BSc, I could certainly write a thesis on this subject.
For more information on the science I am talking about above, you should look up subjects such as spd hybridisation, protonation and Lewis acids and bases, or even Bronsted-Lowry acids and bases. Google and Wikis will be your friends in your search for knowledge.
The theory and science behind what is happening in the plastic is fundamentally sound and I haven't been able to come up with another one that fits the results of the experiments completed so far. Other plastics engineers and guys with science backgrounds support the theory that we have postulated.
It works, and I stand by the process.
Over to you all for comment.
--------------------------------------------------------------------------
I'm happy and can finish writing this all up now.
It's nice when someone proves you right, especially as that guy is way more qualified than I am, although what I lack in qualifications I make up for in experience.
Here's what I posted at Atari Age that prompted the response I posted earlier.
--------------------------------------------------------------------------
I am the alchemist who has been writing all of these articles about de-yellowing plastic. This is my first post on here and it's bound to be controversial....
OK, let's lay this out once and for all as simply as I can. Whilst I am aware that acetal butadiene styrene (ABS) can oxidise under light to form the hydroperoxide as others have alluded to on here, here is one thing that you may not be aware of from the threads, as I am still trying to write this process up for a Wiki, but people keep asking me damn fool questions about it
The process ONLY works in the presence of UV light or sunlight; now, that may not seem like a big thing, but the only molecules in the finished plastic that react so quickly to UV light are Bromine molecules from the Poly Brominated Diphenyl Ethers (PDBEs) in the flame retardant. If you try the experiment in the dark with the same chemicals, the parts don't change colour and just get wet. If this wasn't down to Bromine chemistry in the flame retardant, the polymer would react in any conditions, even in the dark; clearly it doesn't.
The only scientific explanation that fits what we are seeing here is the reaction of Bromine under UV light conditions. Bromine has a single electron spare in it's outer p-shell (Does anyone remember electron shells?). Bromine is 1s2 2s2 2p6 3s2 4s2 3d10 4p5 hence the negative charge of a Bromine radical as it would prefer an even number of electrons. By neutralising it with a single hydrogen created by the catalysis of hydrogen peroxide by tetra acetyl ethylene diamine (TAED) we allow the Bromine to be reduced by the electron and it goes to a stable 4p4 in the outer p-shell.
The key is to use the optimum strength of hydrogen peroxide, which is around 10 to 15%. The white "bloom" you may see is down to peracetic acid which is one of the breakdown products of TAED and this is also a powerful bleach in it's own right. Too strong a solution and it does seem to etch the surface, which is probably the peracetic acid attacking the hydroperoxide of the oxidised polymer as well as working on the bromine molecules.
Now, anyone can feel free to troll this explanation, but after having put months of work and research into this, at least back your argument up with some sort of scientific critique. I am achemist with 25 year's experience and although I may not have a BSc, I could certainly write a thesis on this subject.
For more information on the science I am talking about above, you should look up subjects such as spd hybridisation, protonation and Lewis acids and bases, or even Bronsted-Lowry acids and bases. Google and Wikis will be your friends in your search for knowledge.
The theory and science behind what is happening in the plastic is fundamentally sound and I haven't been able to come up with another one that fits the results of the experiments completed so far. Other plastics engineers and guys with science backgrounds support the theory that we have postulated.
It works, and I stand by the process.
Over to you all for comment.
--------------------------------------------------------------------------
I'm happy and can finish writing this all up now.
patscc
Veteran Member
Oxygen bleaches
Oxygen bleaches
Are you guys sure there isn't some other mechanism at work here ?
The Oxiclean & Hydrogen peroxide are just oxygen bleaches, although I think the Oxiclean might have some ionic & non-ionic detergants in it as well. The PBDE congeners that are popular in fire retardents, at least from the literature, are reported to be pretty stable under UV unless in the presence of non-polar organic solvents, like benzene or toluene. I don't see simple bleaches able to split off the bromine from a PBDE. Besides, isn't the bromine fully bound to the carbons in the Phenyl rings ? If the peroxide is truly acting as a catalyst, it shouldn't get reduced, and from the posts, it sounds like there's some reduction going on.
Plastics yellow for a variety of reasons, anything from resin impurities, to decomposition of stabilizer blends, all the way to titanium dioxide pigmentation used in some plastics absorbing UV & decomposing and the effects NOx compounds have on them.
Anyways, I'm glad it seems to work, although reluctant to use it since I'm a bit leery of the proposed mechanism. This isn't really meant as criticism, I'm just way curious about the actual mechanism.
Here's a good link, by the way, on some of the structural aspects of PBDE's.
http://www.inchem.org/documents/ehc/ehc/ehc162.htm
patscc
Oxygen bleaches
Are you guys sure there isn't some other mechanism at work here ?
The Oxiclean & Hydrogen peroxide are just oxygen bleaches, although I think the Oxiclean might have some ionic & non-ionic detergants in it as well. The PBDE congeners that are popular in fire retardents, at least from the literature, are reported to be pretty stable under UV unless in the presence of non-polar organic solvents, like benzene or toluene. I don't see simple bleaches able to split off the bromine from a PBDE. Besides, isn't the bromine fully bound to the carbons in the Phenyl rings ? If the peroxide is truly acting as a catalyst, it shouldn't get reduced, and from the posts, it sounds like there's some reduction going on.
Plastics yellow for a variety of reasons, anything from resin impurities, to decomposition of stabilizer blends, all the way to titanium dioxide pigmentation used in some plastics absorbing UV & decomposing and the effects NOx compounds have on them.
Anyways, I'm glad it seems to work, although reluctant to use it since I'm a bit leery of the proposed mechanism. This isn't really meant as criticism, I'm just way curious about the actual mechanism.
Here's a good link, by the way, on some of the structural aspects of PBDE's.
http://www.inchem.org/documents/ehc/ehc/ehc162.htm
patscc
tezza
Veteran Member
You can get by very well with less concentrated stuff. I used over-the-counter 6%. Actually this is probably ideal because it IS far less dangerous.
I'm sure that has helped with the cases and keyboards I've done. Although my UV source was sunlight, we have strong UV levels down here due to the lack of both manmade and natural ozone
Yes, I have not seen the slightest trace of plastic degredation in the things I've treated. The results have, in the main, been outstanding.
Two cautions though. I have noticed some fading (not serious) on key and case labels. Also, some badly yellowed keys can appear a little "streaky" at the end of the process.
Its a small price for what now look like almost brand new units though!
Tez
Lorne
Veteran Member
@ Merlin
I bet that was the only response you got from your Atari Age post !
I knew you spoke Greek, I just didn't know you spoke it so fluently
I want to, but I won't just yet, take exception to the % H202 comments. I need to do some more checking (I've got a few gals of my 30-40% stuff left). I seemed to be getting great results with 30-40% H202 in the non-paste application, and while expensive to do, I think that provided the best results.
It's finally warmed up enough (70 F) to go outside, and play around with this again.
50 F and I don't even want to think about going outside and brushing stuff on a computer case! :mrgreen:
@ Tezza
I've noticed no roughening in the surfaces of the pieces I've done either. I've taken to removing the labels and badges before processing, and then re-attaching them later with an automotive type (3M) adhesive.
I can't for sure say that the streakyness (sp?) is caused by the plastic molding process as was posted by someone earlier, because I didn't see that in the solutions I used with just the H2O2/Oxy solution. I saw some lines possibly caused by previous stress fractures in the plastic, but not streaking. When I used the H202/Oxy/X-gum or hair bleach mixture, I did see some some different results.
For now, we know it works.
We will perfect it.
Thanks Merlin.
I bet that was the only response you got from your Atari Age post !
I knew you spoke Greek, I just didn't know you spoke it so fluently
I want to, but I won't just yet, take exception to the % H202 comments. I need to do some more checking (I've got a few gals of my 30-40% stuff left). I seemed to be getting great results with 30-40% H202 in the non-paste application, and while expensive to do, I think that provided the best results.
It's finally warmed up enough (70 F) to go outside, and play around with this again.
50 F and I don't even want to think about going outside and brushing stuff on a computer case! :mrgreen:
@ Tezza
I've noticed no roughening in the surfaces of the pieces I've done either. I've taken to removing the labels and badges before processing, and then re-attaching them later with an automotive type (3M) adhesive.
I can't for sure say that the streakyness (sp?) is caused by the plastic molding process as was posted by someone earlier, because I didn't see that in the solutions I used with just the H2O2/Oxy solution. I saw some lines possibly caused by previous stress fractures in the plastic, but not streaking. When I used the H202/Oxy/X-gum or hair bleach mixture, I did see some some different results.
For now, we know it works.
We will perfect it.
Thanks Merlin.
Terry Yager
Veteran Member
A very good explanation, Merlin, I'm sure, even though I understood about 1.5 sentences of it. So, while I'm not disputing the process, the mechanism by which it works, or the results (which are obvious from the photographic evidence), but I still have some dumb-ass questions. For one thing, I throw some Oxy-whatever into my laundry, and my clothes come out noticeably brighter/whiter, although there is absolutely no light, uv or otherwise, in either the washer or dryer. Also, I'm wondering about those teeth whitening solutions, whose active ingredients are primarily H2O2, but also seem to do the trick in the absence of light inside someone's mouth. What am I missing here? (BTW, I'm also familiar with the fact that even standard chlorine bleach works a helluva lot better if you hang your bedsheets out in the sunlight than without any sun, so there's obviously something going on with ol' Mr. Sol).
--T
--T
Merlin
Experienced Member
@ Terry
That's because the TAED in the "Oxy" doesn't need UV light to work; it catalyses the percarbonates and perborates in the "Oxy" down to peroxides; there is a Wiki on TAED if you look it up, although it is a bit heavy on the chemical formulae.
http://en.wikipedia.org/wiki/Tetraacetylethylenediamine
The UV light is only used to excite the bromines to make them unstable, so that they react with the free radical "soup" we have prepared.
@ patscc
The key word in PDBEs is Poly; there is likely to always be some free bromine left over from a bromination reaction of phenyl ring chemistry, as they usually want an excess to ensure they reach a minimum bromination level. The manufacturer isn't likely to want to neutralise the remaining free traces of bromine and it's my theory is that this is the culprit. It's a weird reaction that maybe we haven't fully got to the bottom of yet, but it works, it's maybe a protonation of the bromine as I stated earlier; think Bronsted-Lowry or Lewis acids and bases.
The other point is that the TAED is the catalyst for the reaction, not the peroxide.
I am having a scientific discussion about it on Atari Age with Harpo at the moment; if anything significant comes out of it, I'll post it here.
That's because the TAED in the "Oxy" doesn't need UV light to work; it catalyses the percarbonates and perborates in the "Oxy" down to peroxides; there is a Wiki on TAED if you look it up, although it is a bit heavy on the chemical formulae.
http://en.wikipedia.org/wiki/Tetraacetylethylenediamine
The UV light is only used to excite the bromines to make them unstable, so that they react with the free radical "soup" we have prepared.
@ patscc
The key word in PDBEs is Poly; there is likely to always be some free bromine left over from a bromination reaction of phenyl ring chemistry, as they usually want an excess to ensure they reach a minimum bromination level. The manufacturer isn't likely to want to neutralise the remaining free traces of bromine and it's my theory is that this is the culprit. It's a weird reaction that maybe we haven't fully got to the bottom of yet, but it works, it's maybe a protonation of the bromine as I stated earlier; think Bronsted-Lowry or Lewis acids and bases.
The other point is that the TAED is the catalyst for the reaction, not the peroxide.
I am having a scientific discussion about it on Atari Age with Harpo at the moment; if anything significant comes out of it, I'll post it here.
Last edited:
Lorne
Veteran Member
@ Merlin:
I may have asked this before, but I've forgotten.
Will the de-yellowed plastic yellow again over time?
If so, will it yellow quicker, or will it take the same amount of time it took previously?
Will the de-yellowing work on a previously de-yellowed piece (ie: 20 years from now)?
I may have asked this before, but I've forgotten.
Will the de-yellowed plastic yellow again over time?
If so, will it yellow quicker, or will it take the same amount of time it took previously?
Will the de-yellowing work on a previously de-yellowed piece (ie: 20 years from now)?
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