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Removing Yellowing from Plastics - Part 4

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    Originally posted by Lorne View Post
    It's a pet peeve of mine, but I think Americans use far too many acronyms.
    Know your TLAs, eh?

    LOL
    Author of the Retr0bright Wiki - http://www.retr0bright.wikispaces.com

    Comment


      Originally posted by Lorne View Post
      It has been stored (indoors at 72 F, in a dark cupboard) in its original plastic tub which looks like it seals OK.
      I've picked up the new Oxy and H2O2, so I'll see what happens.
      Another thought that's been running through my mind is that maybe there's something on the plastic parts, that's stopping the process.
      I've never run into that before though.
      My money's on bad H2O2 or bad Oxy.
      It must have been bad ingredients.
      I got the new stuff, and I could see the difference even when I was just mixing the gel.
      It foamed more, and worked like it had before.
      There's nothing like using fresh ingredients for ANY recipe.

      And here's another example of what can be done with the process.
      It's a Televideo 925 - sitting on some white bond paper.
      The bottom has obviously been processed, and it was as yellow as the top.

      Bottom done..JPG

      Comment


        @ Lorne

        Now you're just showing off.......
        Author of the Retr0bright Wiki - http://www.retr0bright.wikispaces.com

        Comment


          System 80 Retr0Brighting

          Haven't done retr0brighting for some time but the drought has broken.

          2010-07-11-s8016k-de-yellowed.jpg

          The article pertaining to this latest effort is detailed here.

          One interesting thing. At first I had the case under a small UV bulb for 24 hours. Results were quite disappointing. There was a fade in the yellowing but not that much. The next day I re-applied the mixture and put it out in full sunlight. What a difference! In a matter of hours, the case was noticably lighter.

          I think this is a reflection of two things. First, the UV output even in winter sunlight (especially very clean-air NZ sunlight) is much stronger than a small bulb above the case. Also, temperature probably had a lot to do with it. Being winter here, in the unheated garage under the UV lamp temperatures, although not freezing, were quite cool. Out in full sunlight, there was warmth also. This would have assisted the reaction.

          Tez
          ------------------------------------------------
          My vintage collection: https://classic-computers.org.nz/collection/
          My vintage activities blog: https://www.classic-computers.org.nz/blog/
          Twitter: @classiccomputNZ ; YouTube Videos: (click here)

          Comment


            It would be interesting to compare "hard" & "soft" UV light. UV bulbs for "discos" are quite long wavelength ( = low power photons) it saves blistering the punters, but probably doesn't knock so many bromine atoms off their stalks.
            "Don't it always seem to go
            That you don't know what you’ve got ‘til it’s gone" (BANG )

            Comment


              LOL - Well Nige, just how many of those bromine atoms can we afford to give up?
              Surely not everyone was Kung-Fu fighting

              Comment


                Originally posted by nige the hippy View Post
                It would be interesting to compare "hard" & "soft" UV light. UV bulbs for "discos" are quite long wavelength ( = low power photons) it saves blistering the punters, but probably doesn't knock so many bromine atoms off their stalks.
                Yes, that would be interesting. Based on my System 80 experience I think I'll use the sun where I can rather than seek a more powerful blub. I've only got a haldful of items left I need to process. Problem is here in NZ with our changeable maritime climate you can't always order up a sunny, windless day over a weekend. It needs to be a weekend so I can lay them out, keep them pasted, alter their position relative to the source (i.e. sun) now and again and stop pets walking on them.

                Tez
                ------------------------------------------------
                My vintage collection: https://classic-computers.org.nz/collection/
                My vintage activities blog: https://www.classic-computers.org.nz/blog/
                Twitter: @classiccomputNZ ; YouTube Videos: (click here)

                Comment


                  They sell (afaik) hard uv tubes for pond sterilizers, got to be used in a light proof enclosure though (a sterilizers function being to kill cells!). I'm not sure about the ballast required, but at first glance it looks like a standard flourescent.
                  "Don't it always seem to go
                  That you don't know what you’ve got ‘til it’s gone" (BANG )

                  Comment


                    A lot of negative discussion on several lists lately about retrObrite and the harm it will supposedly cause, growing out of a post on cbm-hackers by William Levak, a "chemist [with] some experience testing resins":

                    http://www.softwolves.com/arkiv/cbm-.../14/14545.html
                    http://www.classiccmp.org/pipermail/...ly/289287.html
                    (>30 posts)

                    Anybody want to respond? Merlin? Lorne? Tez?
                    Last edited by MikeS; July 30, 2010, 06:56 AM.

                    Comment


                      Interesting.

                      It’s always good to have different opinions on these kinds of things, especially from people that are trained in the field.

                      My thoughts. Well, the poster is right. No aging tests have been done (that I know of) and there is no harm pointing that out. We use it at our own risk and the more informed opinion there is about those risks the better. There could be long-term damage but who knows? Certainly bloom is permanent. If there is though, is it worse than cheese-yellow? Most cases that need de-yellowing already show brittleness…from prolonged exposure to UV light.

                      RetroBright is a community “project” not a tested commercial product and “use entirely at your own risk” applies. It’s a matter of known and theorized risks vrs benefits. Folk must use it on that basis. I’ve found it great for cream to while cases, where the bloom effect doesn’t seem to show up as the case is a very light color anyway. However, I’m a lot more cautious with coloured cases (grey for example) where it certainly can with overcooking.

                      Testing the effects of Retro0bright would make a great post-graduate project for a chemistry student. I should mention that to the chemistry staff at my University.

                      Coincidentally I’m writing this at 7am in the morning on a beautiful sunny NZ winter’s day. It’s Saturday and I’m about to get up and prepare some retr0bright for a System 80, Atari 800XL and a Video Genie case. My final batch!

                      Tez
                      ------------------------------------------------
                      My vintage collection: https://classic-computers.org.nz/collection/
                      My vintage activities blog: https://www.classic-computers.org.nz/blog/
                      Twitter: @classiccomputNZ ; YouTube Videos: (click here)

                      Comment


                        Well, I agree that we use it at our own risk and I'm certainly not going to guarantee that there is no risk, but I think the tone is a little too pessimistic; there is some real science behind this and I think it does Merlin a disservice when folks say, "good to hear from a real chemist who knows what he's talking about," and I'm not sure that the proposed argument that if x amount causes damage (blooming) then 1/2 x will cause 1/2 as much damage is necessarily very sound.

                        But hey, it's out there for those who think the esthetic improvement is worth the slight risk of a permanent blemish, and those who don't are welcome to keep their cases a nice yellow

                        As to aging tests, it's been out there for close to a year; anybody's cases crumbling to dust yet?

                        m

                        Comment


                          Looks to me like Merlin is a mere amateur, and therefore his contribution is obviously too flawed to be considered legitimate by the vintage computer elite.

                          Big Wink!

                          & regarding blooming, surely if you remove the active ingredients & the energy source, then no further reaction will take place. it certainly looks like those casting aspersions haven't followed the threads & don't really understand the process.
                          "Don't it always seem to go
                          That you don't know what you’ve got ‘til it’s gone" (BANG )

                          Comment


                            Yep, I've retr0btighted a lot of cases now and have been pretty happy with the result. The three I did today came up really well.

                            Tez
                            ------------------------------------------------
                            My vintage collection: https://classic-computers.org.nz/collection/
                            My vintage activities blog: https://www.classic-computers.org.nz/blog/
                            Twitter: @classiccomputNZ ; YouTube Videos: (click here)

                            Comment


                              This is kind of funny.

                              The "chemist”, with “some experience testing resins” mentions that he's read all the information in the Wiki, but doesn't mention that he's actually tried the process.
                              I could give his comments a little more credence if he had done so.

                              He mentions "white bloom", and even for those of us that have used the process, the "bloom" is tough to describe, so not having tried the process, I don't how he can say what it is, let alone say that it is damage to the plastic. It doesn't happen in all circumstances (rarely actually), so is it only damaging sometimes?
                              I consider it more like patchy or blotchy, and on the pieces that I've processed, I found that it's more like an uneven result. The blotchy areas seem to be more yellowed (or unwhitened) than the other areas, which I think is because they haven't been processed enough. With repeat processing (like 5 times) on yellowed Televideo cases, I've found that the blotches disappear, and the whole piece eventually gets back to the original white.
                              How anyone can comment on "damage" to plastics based on the word "bloom" (which is a poor description only due to lack of a better one) without having physically seen or tried the process is beyond me.

                              One of my first pieces (the Osborne 1) still looks like it did when the processing was complete, and the plastic isn't falling to bits. If it falls to bits in 20 more years, so be it. Myself, and all the other Osbornes will probably have fallen to bits by then too.

                              We did all this experimentation for our own use and enjoyment. Someone else's lack of experience and ignorance in the process will not sway my feelings about what we've accomplished, and I don't think it'll sway Merlin's or Tezza's either. There's a load of people out there who have actually done it, who are using it, and are loving the results.

                              There's no substitute for actual experience when you want to comment on something someone else has done. Too bad this "chemist" didn't have any.
                              Last edited by Lorne; July 31, 2010, 07:30 AM. Reason: damn typo

                              Comment


                                Regarding Retr0bright terminology there is "bloom" and there is "streaking". Streaking is what you've described Lorne, where a very yellowed white or cream case de-yellows unevenly leaving yellowish streaks. I've never persisted long enough (or found H2O2 strong enough) to get all of these out but I could well believe it could be eliminated by a lengthy treatment.

                                Bloom appears on coloured cases (grey C64s or grey Ataris) where after a lengthy treatment by someone trying to get the final vestiages of brown/grey out of the case. It's a kind of whitish spotting. I think there are a few photos on the wiki from memory.

                                I've only seen bloom once and that was with a deliberately overcooked C64 case I was using to ascertain the difference between xanthum gum and arrowroot as a thickener.

                                Nevertheless it's important people know about it. Again, it's about risks and benefits.

                                Now I read the post by our resin chemist again, I agree with Mike. The guy is being over-cautious and pessimistic. Retr0bright is not a new technique now. It's been over a year since most of my cases were treated and the plastic seems fine. Bloom, label damage, key label fade and the discolouration of black/blue areas are well known and but avoidable with care.

                                In my opinion cases look far better closer to their original colour that an ugly yellow, green or brown. The risk/benefit equation is heavily in favour of a careful de-yellowing.

                                Merlin has done a great service to vintage computing with this technique. My Colour Genie case processed yesterday looks way better than it did but has some streaking. It will take a lot of NZ sunlight to get that out. The Atari 800Xl looks great and the System 80 is perfect. I'm particularly pleased with the latter as the case was REALLY yellow and it's taken it back to it's original colour with no streaks in evidence at all.

                                Tez
                                ------------------------------------------------
                                My vintage collection: https://classic-computers.org.nz/collection/
                                My vintage activities blog: https://www.classic-computers.org.nz/blog/
                                Twitter: @classiccomputNZ ; YouTube Videos: (click here)

                                Comment

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