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The Case of the Yellowing White Bricks

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  • Pitfall69Pitfall69 0 miles to Legoboy's houseMember Posts: 11,438
    I've used UV light and that didn't do anything near what just placing the parts outside in sunlight. It may be the combination of electromagnetic radiation, infrared and UV that does the trick than just using UV alone. 

    as @CCC said; when HP heats up, it degrades the solution and releases oxygen. I know when it's time to take my parts out from the sun based on all the oxygen bubbles that have formed all over my parts.
  • GomjabaGomjaba UKMember Posts: 20
    Problem is - we barely know how to spell sun in the UK ... we still got 12 degrees here and had like 5 minutes sunshine .. might just park the project until that kicks up or just be more ... patient :) 
    SprinkleOtter
  • dmcc0dmcc0 Nae far fae AberdeenMember Posts: 778
    We've got plenty of sun at the moment, it's just not very warm :(  Given that I had to defrost my car yesterday morning, probably not optimal conditions for putting HP out in the sun, more likely to freeze over rather than warm up.
  • 560Heliport560Heliport Twin Cities, MN, USAMember Posts: 2,377
    edited December 2019
    I experimented with a blacklight bulb- a compact fluorescent, 7-watt ("60-watt replacement"). I put several yellowed parts in 3% hydrogen peroxide with the bulb about 3 inches/75mm away for 24 hours. On the white plate, you can see where I put a 1x1 plate to show the change. On the Medium Stone Grey wing, the 3x6 rectangular section was normal to start, while the angled section was quite discolored. It's now actually lighter than the "undamaged" section! (My apartment faces north; I can't get any direct sun most of the year. The railing of my balcony gets sun in the summer.)
    KungFuKennyAstrobricksBaby_YodaPyrobugLittleLorigmonkey76M1J0E
  • Switchfoot55Switchfoot55 The Northwest, USAMember Posts: 2,191
    Interesting that the black light bulb would do this. I know nothing of light wave length and UV hydrogen-science, so maybe it's obvious to others. 

    I have an aquarium hood light that I guess I could try this with as well. The only weather I currently get is rain... 
    KungFuKennyLittleLori
  • AstrobricksAstrobricks Minnesota, USMember Posts: 4,147
    Black light bulbs emit UV-A rays that cause fluorescent things to light up.
    560Heliport
  • 560Heliport560Heliport Twin Cities, MN, USAMember Posts: 2,377
    I have several crater plates that are yellowed. I put one in a large Sterilite bin with two quarts of hydrogen peroxide, but even with one end propped up, I couldn't get all of the raised part submerged ( duct taped it down) so I added a quart of hot water. Two hours in the sun and it's grey again! The next most yellowed plate is getting it's turn now.
    AstrobricksPyrobugKungFuKennypxchris
  • 560Heliport560Heliport Twin Cities, MN, USAMember Posts: 2,377
    Two white horses from #6044. Only the left side of the horse on the right is severely yellowed, and that piece is pretty uniformly discolored, all sides, even the bottom if the feet- except where the saddle was. The other parts of both horses aren't quite as pristine as this photo shows- they're very slightly yellowed, but the contrast between the two colors is fairly accurate. It's cloudy here right now, but I'm going to put it in H2O2 while I build the sets and see what happens.
    KungFuKenny
  • KungFuKennyKungFuKenny Somewhere between Ice Station Odyssey and FabulandMember Posts: 1,895
    @560Heliport
    Have you noticed how permanent the peroxide treatment is?  I haven’t had any re-yellowing yet but it’s only been a year or so for the first pieces I did.  These are from a couple of weeks ago...

  • 560Heliport560Heliport Twin Cities, MN, USAMember Posts: 2,377
    I probably posted this before but...

    Parts I repaired back to bright white via the hydrogen peroxide method returned back to their yellowed state while in a climate controlled, completely dark closet. The return to the yellowed state happened in roughly two years time.

    So while I was initially very pleased with the result, I no longer will be bothering to try and whiten bricks or more to the point, I won't buy used bricks anymore.
    I'm not sure which parts are the ones I whitened! If they've stayed white, then I can't tell the difference. If @Bumblepants' results are what we should expect, then I don't know if it's worth the effort. On the other hand, at $.84 a quart, H2O2 is cheap. 
    KungFuKenny
  • 560Heliport560Heliport Twin Cities, MN, USAMember Posts: 2,377
    I've just checked the white parts from #6036, #6044, and #6078. All were in the same gallon Ziploc bag for at least the past five years, and I think all three sets have been either built and displayed, or dismantled and stored, together. Two skeletons, eight minifigure with various white parts, lances, shields, banners, a triple feather, and a 2x4 plate. The feather and banners are the more flexible material, and don't seem yellowed at all. All the ABS pieces are the same: very slightly yellowed, but quite good for 25-year-old parts. Only the left side of that one horse is bad. I think the mold release agent theory makes sense here. 
  • 560Heliport560Heliport Twin Cities, MN, USAMember Posts: 2,377
    Oh, and to confuse things further...  I just finished building all three sets, and there are some pieces that are definitely older (more scratched) than the rest, so these are not 100% original. I don't care, but it means the yellowed horse could be from any of my sets that have a white horse. 
  • madforLEGOmadforLEGO Chicagoland USMember Posts: 10,060
    I have a ton of Classic Gray parts (and a 32x32 gray base plate) to try the process on, I just need a clear tub to ensure max sunlight coverage. I do have plenty of H2O2 I got from Walmart (it was on sale).
  • 560Heliport560Heliport Twin Cities, MN, USAMember Posts: 2,377
    Well, after several hours of cloudy skies yesterday, overnight under the blacklight, and several hours of mostly sun today, he's much improved. I'm going to switch him with the horse from #6090; the barding will cover most of the discoloration. If all three parts had been the same, I would have just called him a Brick Yellow horse!
    KungFuKennyIstokgCymbelinegmonkey76vanvonfulljason1976
  • 560Heliport560Heliport Twin Cities, MN, USAMember Posts: 2,377
    @560Heliport
    Have you noticed how permanent the peroxide treatment is?  I haven’t had any re-yellowing yet but it’s only been a year or so for the first pieces I did.  These are from a couple of weeks ago...

    I just checked the 4x6 plate I treated back in December: it's re-yellowed, possibly even worse than before treatment. I took a photo, but it looks white in the photo. Based on that piece over nine or ten months, it's not worth the effort, except maybe for taking photos. Which makes me leery of buying a used set or parts that look nice and white- maybe they've been treated, and in a few months they're going to seem Brick Yellow/Tan.
    gmonkey76KungFuKennyAstrobricksBumblepantspxchris
  • flordflord CanadaMember Posts: 779
    I checked the pieces I posted about in this thread (2-3 years ago?) and mine have stayed white. Mind you, they’ve been in a ziplock bag the whole time.
    560HeliportKungFuKenny
  • CyberdragonCyberdragon Maryland, U.S.AMember Posts: 522
    Retrobright might have some additional chemicals to prevent further degredation. Straight peroxide should work though, what were you exposing them to?
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