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Removing Yellowing from Plastics - Part 4

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    #16
    That looks like exactly the right stuff; hydrogen peroxide, stabilised with a trace of phosphoric acid. It's sold as 'Developer' in white opaque bottles here in the UK.

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

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      #17
      Same here out in the American Midwest, and I even got the cheap stuff. Around a $1.50 a bottle.

      Comment


        #18
        Originally posted by Tupin View Post
        Same here out in the American Midwest, and I even got the cheap stuff. Around a $1.50 a bottle.
        That's cheap (maybe).
        How big a bottle?

        Comment


          #19
          Originally posted by Lorne View Post
          That's cheap (maybe).
          How big a bottle?
          I think 376ml. Seems to be the standard for hydrogen peroxide.

          Comment


            #20
            376 ml = 12.7 oz.
            At $ 1.50 a bottle that's $ 0.118/oz
            With 128 oz in a gal, that's $ 15.10/gal and in small bottles to boot.
            That is the cheapest I've seen it.

            Don't forget the rubber gloves and eye protection.

            Comment


              #21
              How long will it last?

              Hey guys,

              I'd read about Retr0bright a few months ago and thought it was a great idea. Thanks to all involved in developing this!

              Anyway, I'm coming to a point that I need to make a batch to de-yellow some C64 cases and some 1541 cases. I have skimmed this whole thread, but am left wondering about a few things...

              - Do you find that, in principle, a liquid bath does a better/more even job than the gel?

              - If I make a tub of H2O2 + Oxy + Water big enough for the parts I mentioned, how long will it last? Will I be able to do several cases, one after another in the same solution or will it stop working after X amount of plastic has been exposed or some amount of time?

              - Should I add more Oxy over time?

              - Does it make any difference if I use tap water or should I use distilled water?

              - Has anyone found a good ratio of H2O2 (strength?) to Oxy to Water for larger batches?

              Thanks for your thoughts and any guidance you can give me!

              -F

              Comment


                #22
                @falvesjr:

                Granted reading parts 1, 2 & 3 would be quite a chore, but the answers to your questions are contained in those parts.

                - A liquid bath probably does a slightly better job than a paste/gel, but it is prohibitivly expensive, and a little more dangerous (it's tough to spill or splash a gel/paste).
                - I've found that the H2O2 & Oxy mix will last about two days, and then it's spent.
                - If you add enough Oxy the first time, you shouldn't need to do anything other than stir the stuff once in a while.
                - No idea, I never diluted the 30% H2O2 that I was using.

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                  #23
                  Got a mixture going, used corn starch instead of xanthan or guar gum, I used most of the container to get it to a stage where the mixture is behaving like a non-Newtonian fluid, and put some on top of an ADB mouse. It is definitely bubbling, and I have a good feeling about this.

                  Comment


                    #24
                    Originally posted by Tupin View Post
                    Got a mixture going, used corn starch instead of xanthan or guar gum, I used most of the container to get it to a stage where the mixture is behaving like a non-Newtonian fluid, and put some on top of an ADB mouse. It is definitely bubbling, and I have a good feeling about this.
                    You are aware that by using the RetroBrite process, you are required to take and post before and after photos, aren't you?

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                      #25
                      Took a before picture, I'll take an after picture if it turns out.

                      It's like all dried up at this point except for a few parts, I'm trying to keep it from turning rock hard by mixing it around a little.

                      Comment


                        #26
                        Originally posted by Tupin View Post
                        Took a before picture, I'll take an after picture if it turns out.

                        It's like all dried up at this point except for a few parts, I'm trying to keep it from turning rock hard by mixing it around a little.
                        The paste or gel will dry out somewhat, and reapplication will be required, if the desired results haven't been achieved yet. That's completely normal.
                        You can also just grab a paint brush and mix what's already on the parts around a bit (and then maybe add some more). I would think you'll need the stuff on the parts for at least 6 hours using 12% H2O2. And if you're doing this outdoors, it will dry out much quicker. There are no hard and fast rules for this - you get the hang of what to do in what situation, after you've done it a few times.

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                          #27
                          I'm going to have to do this again, it did get something off, but it barely brightened it at all. I probably used too much corn starch, I forgot that it would dry up quickly when it set....

                          I'll post pictures of it when I get it right.

                          Comment


                            #28
                            You are doing fine, Tupin; stick with it....kitchen chemistry rocks, doesn't it?



                            @ falvesjr

                            1. Tap water is fine.
                            2. A bath of liquid is ideal, but the gel scores over the liquid for large areas.
                            3. If you make up 10-15% H2O2, you will be able to treat a few cases and a bath of liquid will last 2-3 days tops.
                            4. 10 to 15% is the "sweet spot" for the H2O2, where you get the quickest results without causing the white 'bloom' effect.
                            5. Adding more Oxy won't make that much difference; you may speed things up initially, but the liquid will be spent quicker. Slow is good with this process and let's face it, 2 days to remove 20 years of yellow isn't that long, is it?
                            6. The yellow colour is only a few microns thick, so the area that can be treated is huge, actually.

                            Does that answer your questions sufficiently?
                            Last edited by Merlin; September 3, 2009, 10:47 AM.
                            Author of the Retr0bright Wiki - http://www.retr0bright.wikispaces.com

                            Comment


                              #29
                              Originally posted by Tupin View Post
                              I'm going to have to do this again, it did get something off, but it barely brightened it at all. I probably used too much corn starch, I forgot that it would dry up quickly when it set....

                              I'll post pictures of it when I get it right.
                              Are you using the sun or a lamp? UV levels in the sun are much higher (at least where I live) and I've found de-yellowing is much faster than a lamp. You just have to be careful the mixture doesn't dry out.

                              I used arrowroot for my first units and that tended to dry out quickly too, like your corn starch. Reapplication works, but I've found Xanthan gum doesn't dry out so fast, even though it requires careful mixing initially.

                              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)

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                                #30
                                Tezza

                                The difference is that Xanthan Gum skins over slightly and this slows the drying out down quite a lot. Corn Starch and Arrow Root don't have the same property.

                                No-one has tried it yet, however I believe that wallpaper paste may have similar properties to Xanthan Gum, but may be easier to disperse.
                                Author of the Retr0bright Wiki - http://www.retr0bright.wikispaces.com

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