Reversing "yellowing" of 70s/80s style plastics - Page 1
Forum section: electronics / testgear

author: madshaman
author_rank: Frequent Contributor
timestamp: October 10, 2013, 07:15:35 pm
content: Hi everyone, I've heard there are some "magical" solutions for de-yellowing that range of white->beige plastic that was used for chassis and controls in the 70s and 80s.Anyone have experience doing this themselves and anyone have a sure-fire technique.Any info is welcome from how to determine the type of plastic and how to go about de-yellowing it.

author: grego
author_rank: Frequent Contributor
timestamp: October 10, 2013, 07:27:08 pm
content: It's usually the bromine they use as a fire retardant. You can generally clean it with hydrogen peroxide.

author: JDubU
author_rank: Frequent Contributor
timestamp: October 10, 2013, 07:29:40 pm
content: This link might be of interest:http://68kmla.org/forums/viewtopic.php?p=93761

author: tmammela
author_rank: Contributor
timestamp: October 10, 2013, 07:30:54 pm
content: I tried this out today:http://retr0bright.wikispaces.com/Retr0Bright+GelGlad to say it works even with fluorescent light. I used 6% hydrogen peroxide, cheap version of oxi-action and corn starch. After two hours, great difference, but UV light would be good for anything more than light yellowing.

author: Carrington
author_rank: Super Contributor
timestamp: October 10, 2013, 07:47:50 pm
content: Quote from: tmammela on October 10, 2013, 07:30:54 pmI've tried it on a Commodore Amiga 1200 and it works perfectly.

author: madshaman
author_rank: Frequent Contributor
timestamp: October 10, 2013, 08:15:49 pm
content: Brilliant guys, thanks for the great info including the bromine hint!

author: marshallh
author_rank: Unknown
timestamp: October 10, 2013, 08:18:17 pm
content: Works great, do make the gel, its way better than the liquid. If you let the mixture go too long you will "scorch" the plastic edges and they'll have crusty white artifacts. Once you see this barely starting to occur pull it out and clean it off.Also, your plastics will re-yellow AGAIN UNLESS you clearcoat with UV protectant. The cycle will just repeat itself, but faster this time. Nobody remembers to do this because it can take 2-3 years but it will be worse than it was before.

author: xrunner
author_rank: Super Contributor
timestamp: June 25, 2017, 06:51:27 pm
content: Thought I'd resurrect this thread because I'm doing a plastic restoration right now. The patient is a GW Instek GDM-8251A. First pics are the initial conditions of the plastic. As you can see it's pretty yellowed where the rubber boot didn't cover it. The white area where the button labels are, is not the same plastic, it's covered by a sticker. If you look around the edges you can see where the rubber boot didn't quite cover the white plastic.Also, the gray handle is yellowed also, so will do the same treatment to that as well.What I'll be using, which has proven to work very well many times, is a gel-like peroxide you can get at hair salon supply shops, shown below. I'll put up more pics as I get it prepared ...

author: nidlaX
author_rank: Frequent Contributor
timestamp: June 25, 2017, 08:27:51 pm
content: Quote from: xrunner on June 25, 2017, 06:51:27 pmA word of caution regarding hair salon products: some of them also contain phosphoric acid in unknown concentrations. Not a big deal most of the time since the concentration should be low, but phosphoric acid does not interact well with certain types of plastics. Beware if you plan to soak your plastics for extended periods of time.Quote from: marshallh on October 10, 2013, 08:18:17 pmIt's not even clear that the bromine re-surfacing is due to UV. I've heard reports that the plastics will re-yellow even when stored in the dark.

author: xrunner
author_rank: Super Contributor
timestamp: June 25, 2017, 10:13:39 pm
content: Quote from: nidlaX on June 25, 2017, 08:27:51 pmNever had a problem using it here yet, but all these home remedies come with the same disclaimer -"Use at your own risk"Got the meter faceplate prepared. Need to remove everything because your going to have a gooey mess on it and will need to be washed off. Brush on the peroxide and cover with saran wrap so it doesn't dry up in the sun. Then place out in the sun for a few hours and check on it. Preferably next to a ceramic frog.

author: tablatronix
author_rank: Regular Contributor
timestamp: June 25, 2017, 10:41:41 pm
content: Are you gonna try to clean the boots? I would like to see how that goes also. They appear to be TPE plastic, I got some hits on google from sex doll forums, same material apparantly.

author: xrunner
author_rank: Super Contributor
timestamp: June 25, 2017, 11:28:32 pm
content: Quote from: tablatronix on June 25, 2017, 10:41:41 pmThe rubber boots? When I got the meter I washed them in warm soapy water. That's all I see that they need.But I checked on the plastic -Lookin' great! Will update later today or tomorrow but the process is working as planned.

author: cdev
author_rank: Super Contributor
timestamp: June 25, 2017, 11:44:45 pm
content: Musical comment on above (or below) previous"I blew up her body, but she blew my mind"

author: macboy
author_rank: Super Contributor
timestamp: June 26, 2017, 01:04:26 pm
content: Just last week I fixed up a yellowed Keithley 2400 front panel using this technique. Worked like a charm. This was not my first time. I've done maybe 10 front panels of various gear now. I use "40 vol" (very high strength) gelled hair 'bleach' (peroxide). I donotadd anything such as oxy clean (some say this is a needed activator, not in my experience).Here's what I do:- put on eye protection and a pair of Nitrile gloves. Or two pair, even better. You donotwant this stuff getting onto your skin or eyes. It is strong enough to badly burn.- wash the part very well with soap and water then rinse and dry. Oily surface will prevent the water-based peroxide from working.- Paint the gel onto the surface of the plastic, trying to keep it on the problem areas (i.e. avoid display lens, etc.)- place part into a glass or ceramic dish with high enough lip to clear the item.- cover with one layer of plastic food wrap to prevent evaporation.- place in full mid-day sun- rotate every 5 minutes to get even UV exposure.- After literally only 20 to 30 minutes (for light/moderate yellowing) in the sun, the job is done. It should not take hours and hours. If it does, you have ineffective chemicals, so find something better. For very deeply yellowed stuff, re-apply gel every 20 minutes, and don't expect a miracle, it may never get there.- Rinse extremely well under running tap water for several minutes. Use a brush to ensure you get into all the nooks and crannies.- Blow dry with compressed air - the gel won't blow off as easily as water so you will see if you missed some.I have found that the silkscreen on the Keithley stuff is not harmed after just 20 minutes. However, when experimenting with materials and methods years ago, I did have one soaking for many hours, and when I rinsed it, the silkscreen ink had softened enough to rub off under my fingers. D'oh. Be careful.

author: ebastler
author_rank: Super Contributor
timestamp: June 26, 2017, 01:55:39 pm
content: Quote from: macboy on June 26, 2017, 01:04:26 pmThank you, macboy; great instructions. I would add one comment:For the above two steps, wear safety goggles!You don't want little droplets of hydrogen peroxide reaching your eyes...

author: xrunner
author_rank: Super Contributor
timestamp: June 26, 2017, 01:59:27 pm
content: Complete success!

author: macboy
author_rank: Super Contributor
timestamp: June 26, 2017, 02:44:28 pm
content: Quote from: ebastler on June 26, 2017, 01:55:39 pmGood point, edited my post.

author: xrunner
author_rank: Super Contributor
timestamp: June 27, 2017, 12:08:28 pm
content: After I clean the plastic I rub Armor All on it. Makes it look new plus it has a UV inhibitor in it. And by the way, if you have Armor All in a white plastic bottle and you can't see the liquid, youdohave to shake it up. It settles out - see pic.