mister Posted June 21, 2015 Share Posted June 21, 2015 i have some small ABS plastic parts and i wish to "yellow" them a bit, the kind of yellowing that you often see from sun damage or just over a long time like how old gray computer keyboards often discolor over many years.I would like to construct some kind of small box or device that i can put outside in the direct sunlight, and put the small parts inside this device, and have it intensify the UV light / rays / exposure to the small parts so that it speeds up whatever the yellowing process is.So my question is, how can i accomplish this? How can i magnify or intensify the light without totally melting or destroying the parts? I should also note that i want the exposure to be uniform and not concentrated in one tiny little area like a magnifying glass would do. Link to comment Share on other sites More sharing options...
StringJunky Posted June 21, 2015 Share Posted June 21, 2015 Put them on a flat white surface with a flat white background reflector. You don't want to cover them with clear plastic or glass because that filters some of the UV.. Orientate the reflector so that it captures most of the sun through the day.and turn the items around and over everyday.. Link to comment Share on other sites More sharing options...
mister Posted June 21, 2015 Author Share Posted June 21, 2015 is there no way to do it more uniformly? For example i know that if i want to REVERSE yellowing i just put them in a bowl of hydrogen peroxide and leave in the sunlight and it uniformly reverses all yellowing in just a few hours or days Link to comment Share on other sites More sharing options...
StringJunky Posted June 21, 2015 Share Posted June 21, 2015 is there no way to do it more uniformly? For example i know that if i want to REVERSE yellowing i just put them in a bowl of hydrogen peroxide and leave in the sunlight and it uniformly reverses all yellowing in just a few hours or days If you have them free hanging off wire/string in front of the reflector that would be better, but, nevertheless, the idea of the reflector is provide more uniform coverage all over the items. The reflector wants to be as close as possible such that the rear of the items is not in shadow. if you suspend them, any breeze will cause them to rotate. Link to comment Share on other sites More sharing options...
mister Posted June 21, 2015 Author Share Posted June 21, 2015 the thing is that i want to be able to do this for a bunch of parts at once, too. not just a single part at a time. Also if i used the string wouldnt the area under the string not get yellowed ? what if i used clear string or seran wrap / cellophane to suspend the parts ? would that allow the parts to yellow completely and not leave any area unyellowed ? i was searching for hot dog cooker images just now, do you think there is a superior design to use ? also is there some kind of "white reflector" product i can buy ?? Link to comment Share on other sites More sharing options...
StringJunky Posted June 21, 2015 Share Posted June 21, 2015 How big are the bits? You could get some cheap monofilament fishing line that is clear. 10lb breaking strain should do you.. Wrapping anything around the parts will lengthen the time to yellow. Polystyrene sheet is light, workable and and cheap. Some wide adhesive white to join the faces together. You could just use a white cotton sheet suspended even. Depends how many times you are going to do this, but anything you can find should be good enough to test the idea. Link to comment Share on other sites More sharing options...
mister Posted June 21, 2015 Author Share Posted June 21, 2015 i have some small ABS plastic parts that i wish to "discolor" or in other words "yellow" chemically and want to know how this might be achieved. The type of yellowing i am after is the kind you frequently see with old gray computer keyboards or mouses that have yellowed over time. Or if plastic has been left outside for a while and has yellowed from sun damage. I want a moderate version of that. ironically, I know how to REVERSE yellowing for my parts, by immersing them in a bowl of Hydrogen Peroxide and leaving outside in direct sunlight for hours or days, and they become white as new, all discoloration is reversed quickly. But now i want to know how to speed up the yellowing process into something that i can consistently do, in bulk, in a relatively short time frame. There must be a way to do this chemically. Looking forward to your suggestions Link to comment Share on other sites More sharing options...
StringJunky Posted June 21, 2015 Share Posted June 21, 2015 One of the chemists might know a suitable oxidising chemical. As far as I could find out, UV accelerates the reaction with oxygen to cause yellowing. Link to comment Share on other sites More sharing options...
mister Posted June 21, 2015 Author Share Posted June 21, 2015 right, i am interested in all possible options, from physics to chemistry. I have been trying to find out what the actual cause of yellowing really is but i cannot quite figure it out. Is it because heat, or uv light, causes some chemical within the plastic to come out ? Perhaps if i could understand this, it might give further insight into ways of accelerating the process Link to comment Share on other sites More sharing options...
mister Posted June 21, 2015 Author Share Posted June 21, 2015 They are Lego parts so they come in many shapes and sizes but in general anywhere from a small bead size to a larger part like 2 inch by 4 inch plate for example Link to comment Share on other sites More sharing options...
StringJunky Posted June 21, 2015 Share Posted June 21, 2015 plastics.pdf Link to comment Share on other sites More sharing options...
John Cuthber Posted June 21, 2015 Share Posted June 21, 2015 Polystyrene absorbs a lot of UV- in particular it absorbs the UV that polystyrene absorbs (yes, I know that's tautology). How well do you expect it to reflect the UV that's absorbed by ABS? (The S in ABS stands for styrene). The cotton sheet is a better idea, but wash it without laundry detergent a couple of times to remove the fluorescent brighteners. Incidentally, most white paint is largely based on titanium dioxide which also absorbs UV heavily. Aluminium foil is probably as good a suggestion as anything,, but if you focus the sun too well you will melt the plastic. 1 Link to comment Share on other sites More sharing options...
StringJunky Posted June 21, 2015 Share Posted June 21, 2015 Polystyrene absorbs a lot of UV- in particular it absorbs the UV that polystyrene absorbs (yes, I know that's tautology). How well do you expect it to reflect the UV that's absorbed by ABS? (The S in ABS stands for styrene). The cotton sheet is a better idea, but wash it without laundry detergent a couple of times to remove the fluorescent brighteners. Incidentally, most white paint is largely based on titanium dioxide which also absorbs UV heavily. Aluminium foil is probably as good a suggestion as anything,, but if you focus the sun too well you will melt the plastic. Cheers. Learnt something today. Link to comment Share on other sites More sharing options...
Sensei Posted June 21, 2015 Share Posted June 21, 2015 Why not try UV discharge tube (Deuterium?), or UV lap, instead of relying on Sun light.. ? Link to comment Share on other sites More sharing options...
hypervalent_iodine Posted June 22, 2015 Share Posted June 22, 2015 ! Moderator Note Similar threads merged. One thread per topic, please. Link to comment Share on other sites More sharing options...
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