Adam Savage Restores Clear Plastic Discoloration
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- Опубліковано 14 жов 2024
- As a quick follow-up to his recent One Day Build for his Nagra IV-S audio recorder, Adam attempts to renew and restore the discoloration of its clear plastic lid, using a combination of hydrogen peroxide and plastic polish compound. Let's see if it's possible to bring this precious plastic covering back to its former glory.
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Thanks for watching!
Like others have said, a UV light makes the hydrogen peroxide process work so much better. I use it for cleaning yellow discoloration from plastics (both solid and clear). The addition of a UV light (and letting to process go for 24 hrs or longer for really bad yellowing) makes a world of difference.
Agreed, UV light is a critical part of the process
I've done it too on old computer cases and a clear stereo cover and UV light is the difference, I also used a stronger HP% I think it was 30% not 12%. The computer cases came out off white/beige just like from the factory floor and the clear plastic was crystal clear without a hint of yellow like this still has.
I coated them before bed let them sit overnight then set them out in the driveway for a couple hours in the sunlight, then cleaned them off. 10-11 hours total.
This Summer I de-yellowed a load of LEGO bricks, worked well, but being the UK and not having a garden to leave it in, the window of opportunity isn't great! Soon I'm making a de-yellowing box with a glass tub (ideally lidded), UV LED strips and some kind of heating base.
Very Deep Dive on this ua-cam.com/video/YPl356YKcVs/v-deo.html
Tip: If you don't have access to UV light another good source is the sun itself. Just make sure to swirl the parts from time to time to get a uniform color. I whitened the body of a white Panasonic Flip Clock. Works a charm
12% hydrogen peroxide is more than enough concentration, but as everyone has said UV exposure is needed. If it doesn't fit in Adam's beautiful UV box for finishing 3D printing, just sitting in sunlight will do.
Honestly, the Nagra looks gorgeous already. Gave me a small thrill to see it zipping tape through rewind!
Issue with sunlight is that the perioxide will turn to water much quicker.
In March last year Adam built a UV curing oven for 3D prints using led UV strips, those same led UV strips arranged over the top of the peroxide container would activate the peroxide and give an nice even result.
Wonderful work! My only advice here is your use of paper towels on plastic: it does put microscratches into the surface. Cotton or poly microfiber cloth is the only thing to use to prevent clouding or hazing a plastic surface. Remember when you were a kid and the optometrist warned you about cleaning your glasses with paper towels? That was good advice!
Funny thing is that those blue ones he puts the lid on look like microfiber cloths, yet he still continues to use those paper towels 🤦♂
@@pendaco They are thin Huck towels; you can find them listed through his online Amazon shop link. I agree that a new microfiber cloth would be my choice.
I just posted the same comment about five hours after you, didnt read down the comments this far. Sorry. but it is worth mentioning more than once I hope.
I know it's a year old, but seeing this brought back some bad memories. I used to work in a glass shop, and had to redo a few projects, because the other genius guys that SHOULD have known better, came up and started cleaning the plexi/lexan with paper freaking towels! AFTER I was almost done!
As a teenager I used to clean my glasses with paper towels and windex all the time. Nobody ever told me it was bad. Finally once when I went to get a new pair of glasses they seen my glasses and knew immediately what happened to them. I now use special cleaning solution for glasses (no ammonia) and a lens cloth.
The most likely reason it got worse the more you polished it is most likely because you didn't clean out your pad often enough combined with allowing the polishing compound to get too dry on the surface while still buffing. After a couple of passes over an area with your buffer the area needs to be cleaned off as well as the buffing pad. Then new compound can be applied & worked again if it needs it. When polishing compound gets too dry it turns into a much coarser abrasive because the liquid is lessened but the grit is still there. As others have stated hydrogen peroxide works well to remove yellowing from plastics but it requires ultraviolet light & potentially more time than you allowed. You would also want to flip the cover over halfway through to help the bleaching process penitente the whole piece.
He really should be using the polishing pads that are made of foam. That way you can use different foams based on how much scratch removal you need and then finish off with a gentle polish to get the shine out of it.
Speed as well, but it sounded like a low RPM.
I agree. I've been buffing cars for over 20 years & I use less compound with a spray bottle of water. One thing I did learn from this vid, is that there is plastic polish. I just never thought of that before. Cheers Y/All.
I was cringing every time he contaminated the finer grits with the coarse ones still on the pad. He should have dedicated pads for each grit. I've buffed out lacquer finishes on guitars. It's an unforgiving process.
@@raoulduke8382 It's pretty obvious that Adam didn't know much about buffing. But look at all the other things he's done. No one knows every thing. That's how we learn in life. Gotta give him a break.
I love watching you in your shop. I thought i was the only one that spends 30% of my time working on a project just wandering around aimlessly looking for something.
I just love it when products are screwed together in stead of glued or snap-clicked.
Since those are so rare and hard to find you should make a couple vacuum molds of it for safekeeping. You never know when having that specific shape might come in handy down the road.
It sounds like there's collectors that might want a replaca if they can't find an original.
Outstanding idea!
Yes, we do want and need it. Dust covers for reel to reel players are essential. @@drewc1197
If you want your mind blown when trying to remove scratches from plastic, try Polywatch polish. It doesn't work on all types of plastic, but the results on acrylic based plastics are amazing. I refurbish old watch crystals from scratched beyond being able to see through, to completely clear, in minutes. Never bought anything that actually worked this amazingly before.
There is a restoration process called retrobright that uses hydrogen peroxide and UV light to get the yellow out of old plastic. People have restored old PCs and all sorts doing this. One setup I’ve seen is a clear container filled with hydrogen peroxide, wrapped in UV led tape and then tinfoil. I’ve also seen hydrogen peroxide cream from beauty suppliers work well as it can stick to the surface you want to restore, wrapped in cling film and left in the sun.
Just the little tasks in life makes for a better world.
Keep inspiring us.
Watching the de-yellowing is one of my favorite practices on Odd Tinkering, though he is always dealing with opaque plastics.
When one of these comes out well, it's such a kick to see the smile on Adam's face. You just know he's satisfied when you see that smile!
Imagine how shiny the inside of the plastic polish bottle must be.
Everyone’s already mentioned UV light, I just want to know how Adam managed to read about the peroxide without coming across the UV part.
Sad, right?
It’s possible he didn’t think it mattered because often the UV is suggested to make it work faster when it in fact is needed to get it to work at all
Ye that's what wondering too. Nearly all the articles on Internet mention the UV
I use a UV lamp too. I’ve seen where some people put it outdoors, in the sun for a few days. But that seems to be a lot of trouble.
He is human like the rest of us. He just missed it or misunderstood how critical it was
Seeing Adam on here, is like seeing an old friend. I haven't thought about him in a long time.
Mother’s Aluminum Wheel Polish
Works amazing!!!! Perfect for car headlights too. Available at just about any auto parts store. Trust me, it’s AMAZING on plastics! Perfect for yellowing like this.
I build plastic models and use what used to be called Future Floor wax, but now called Pledge Floor Care for the clear parts. I've found that minor scratches mostly disappear as it fills in the scratches. Not sure if it will work, but just a suggestion. I've usually dipped the parts in the floor wax but have used an airbrush on them before. It doesn't need thinning.
There is something about watching an actual genius work on anything.
Hi Adam, as others have said the hydrogen peroxide will work, but needs UV light to do the trick.
Research in the Pinball area and you'll find great tips for removing yellowing with minimal integrity damage. We commonly treat this kind of stuff to restore older machines. Depending on your plastic type the time and method may be different to reduce potential damage. For this type of likely PC plastic you do have to submerge it in the peroxide and keep it in full UV sunlight until it clarifies. Anywhere from 2-72h depending on your UV intensity. It's the least effort and least damage that won't reduce the clarity or polish. I'm not sure if it's the peroxide reacting with the plastic or the reaction of UV through peroxide that somehow modifies it. On some plastics just leaving it in direct sunlight for a few days will do the same. It's the safest way for any plastic.
If possible do this outside in full light, not in a window because windows (especially modern) cut certain UV wavelengths enough it will take 48-72h to clear. Storm windows often have UV film and this may not work at all indoors. You can also try making a paste from baking soda or certain types of toothpaste and let that sit if sun isn't an option. Some plastics will warp depending on sun/heat/cold so indoors in the window may be required. I'm not sure what UV wavelength makes this process work, wish I knew, but I've only gotten it to work in full sun. Also works safely on PP.
Be cautious about the methods. For anyone doing this stuff DO A TEST FIRST, these things can brittle some plastics depending on chemical properties and age. Some ABS will re-yellow pretty quickly when doing these methods and depending on the plastic formulation it may make it brittle. You may need to seal the plastic to keep it from yellowing again because it's oxygen that causes the yellowing. I've seen people ruin items doing some of these de-yellowing methods. Most of the methods will remove stickers, paints, or embellishments so even more important to do a test. You can do this with just a drop on a more inconspicuous part.
I had about the same issues with the Novus polishes on my motorcycle windshields - it seemed to do well at first, then it got worse, then I was fighting to get it back to a respectable clarity. I ended up getting Meguiars #17 (mirror glaze clear plastic cleaner) and it's worlds better at removing fine scratches than the Novus products are. It's safe for gauge clusters, computer screens, and motorcycle windshields, where optical clarity is required (I was almost blind riding at night due to the glare from the swirls on my windshield originally). Thanks for posting!
Thanks for this. All the other comments about polishing didn't seem to know that he was using a product that wasn't a mechanical polish. Your comment was actually helpful to me because I have used the novus fine (can't rmember if it's 1, 2, or 3) on opaque plastics and it works nicely and they seem quite shiny, but clarity on clear plastics isn't great. I think his effort was improved greatly by giving it a good cleaning after the final application. Thanks for your tip!
The peroxide + UV light de-yellowing process is called retr0bright. Lots of vintage computer UA-camrs use it to fix plastics on old computers/electronics. Super-cool to see you using the process on a such a neat machine :)
Hey Adam, When do we get to hear some recordings from this thing? I would love to know what it sounds like! (Beautiful work on the restoration)
As many others have said, this works best with UV light. I'd try it again, while also leaving the part exposed to a UV lamp. Sunlight also works, but you might not want to risk it warping from the Sun's heat.
Adam - Here is Why it got Worse and how to fix it- you need to move from a cutting compound to a polishing compound. Both are like liquid sandpaper, with the cutting compound being a low grain and the polishing a very fine grain. It got worse the second time because you had already weakened the surface you were working on and needed to smooth out the scratches you made with a finer grain (polishing compound). Keep working on it, thing about getting a foam polishing pad to use with your polishing compound and then when it's finally clear and devoid of scratches think about covering it with clear coat to prevent the yellow from ever coming back.... put practice on other less valuable pieces of clear plastics first because if you fuck fuck up the clear coat you have to go back to square one with the clear coat. You will also need to wet sand and polish the clear coat but it will last longer.
I use hair bleach peroxide %35 and uv light to restore icy clear soles on my sneakers. It works to remove the yellow for sure
Edit: I hadn't read the comments about uv light but they're right.
Now back to watching the rest of the video 🤓
Do you think regular bleach would work? I feel like bleach would work better than peroxide.
@@Guinea54 bleach causes yellowing and for the material to ultimately breakdown it's really harsh
@@h.Freeman interesting.. I have a watch that has clear straps that might turn yellow so I will keep your method in mind for when that time comes. Would sunlight work as good as the UV light
Awesome, Novus is a 3/4 part system and you have to use the final polishing compound in order to get that shine back fully, it also takes out the rest of the micro scratches for a mirror finish. I use this stuff for model kits and old kit glass that has yellowed and gotten beat up pretty bad bouncing in the box for a few decades lol. Love all you do!
WE THE INTERNET ABSOLUTELY NEED TO GET ADAM TO DO THIS AGAIN WITH THE UV
Thanks for taking us along for the ride.
Adam, I do sneaker restoration and I use a product called Salon Care 40 to remove the yellowing on white rubber of the sneakers.
The secret is to coat with the salon care and put it under uvb light and it works great.
Hunters use it was well to whiten game skulls.
I think if when you were soaking the cover if you would have had it under some uvb light it would work.
I love the work prep. Wipe it out with the first old rag that I find and call it good.
Sunlight!!! That and peroxide has saved countless yellowed vintage Lego for me
Yep, that was me yelling at the screen “NO PAPER TOWELS - THEY SCRATCH!” Then followed it with “You totally missed the ultraviolet light step!” Aaaugh!
I already wondered why I was hearing an echo 😄
There's been some really great experimentation done with the retrobrite process, and one conclusion that they've all pretty much come to is that heat and/or UV is key to making the process work. Since this is a very valuable piece you may want to avoid going with the heat option since it increases the risk that you might overheat the piece and warp it, but it definitely would be worth it to get some UV lights and repeat this experiment. The other option would be a higher concentration peroxide solution, but once again it becomes risky at a certain concentration, and without UV and/or heat results are likely to be middling at best. The absolute best results seem to be obtained by using both heat and UV, but even just UV should give you better results than what you got.
Yo a tattoo of a ruler is the advice I never knew I needed. I'm constantly looking for a measuring stick this is life changing
I still have my TEAC 3300 reel to reel I bought around 1971. And, it still works.
After all the videos on weathering new things to make them look old, you finally get something that already looks old and you do this?! 😉
A strong UV light source helps catalyze the oxidation process in the peroxide bath. A bit counterintuitive, since UV light over the long term is also what tends to cause the plastic to yellow in the first place, through the formation of free radicals in the plasticizers and stablizers.
To get rid of scratches, you might want to try dipping in “Pledge Revive it” floor gloss. I use this on the windows canopies of my models. Prevents fingerprints from the glues and give them a more natural glass look rather than the “clear plastic” look
For hard clear plastic (like headlights) I use the 3M advanced headlight restoration kit. The polish that comes with the kit leaves the plastic with much better clarity than other kits I've used.
The 3M kit is used with a cordless drill and has 500 and 800 grit sandpapers and a 3000 grit Trizac scuff remover and then you finish with a foam pad and what they call a rubbing compound.
Dry sand with the sandpapers and use very light, even pressure. Then use more pressure and some water when using the Trizac pad. Finish with the foam pad and polish until the plastic is clear.
Check your work to make sure you've removed all of the scratches from the prior step. If you see any "ghost" scuff marks or cloudiness it means you didn't remove all of the marks from one of the abrasives along the way and need to start over being sure to be very thorough.
To get crystal clear results, spray the plastic with the acrylic clear coat that comes in Maguiar's headlight restore kit. Make sure the surface is free from dust and lint before applying the clear coat. Something about that particular product lays down very evenly as compared to other clears I've used. Do not over spray.
I would not recommend this last step for wide, flat surfaces. In my experience it's damn near impossible to get a perfectly even coat.
Anyways, your results speak for themselves and I'll be giving Novus a try.
" ahh you are a set screw!"
.
of course you are because you are part of a beautifully engineered piece of technical art that was built to last and function well from back when things like that actually focking mattered.
.
and oh yeah well-expressed joy about the perfectly sized tray. I can so so so relate omg.
This reminds me of the process for restore headlights. You buff off the outer oxidized layer, and then add a clear coat spray.
I just got into reel to reel myself. what kept me away was the seemingly daunting way it operates but once you get the hang of it its easy as hell. i got a sony tc series player and an external matching vintage preamp (it doesnt have its own speakers onboard). i have then proceeded to rescue and save old radio station airchecks and a couple home recorded beatles albums to play on it. amazing stuff. i always make sure to keep about 4 feet of leader added on all the tapes. sounds like a lot but it isn't, as you need to make sure there isnt such a high tension on the tape ribbon. acetate ones like to snap,
Thanks. I learned a few things. Before and after photos would have been a great addition.
That looks amazing, I actually like the tiny bit of yellow, makes it look like some kind of crystal after that polish
Looks nearly factory-fresh, nice job. Just a note on your last Nagra project, the handle, for the ultimate class act the screws that attach the handle to the side pieces should be countersunk flathead screws, an easy rework. I'm sure Nagra would have done it that way.
As far as I've seen videos of Peroxide and Baking Powder together make it go to almost perfectly clear again.
That's really interesting, it suggests the yellowing is surface only and could be removed by ablating the surface, that might work really nicely for opaque surfaces that are textured
Yeah, I'm curious how good it'd do cracks & crevices
...that smile says it all.
Plus I'm of the mind that removing all signs of aging is unnecessary. 😊
Were you actually using paper towels on plexiglass? Undoing all the work you accomplished with the polisher? Just wondering.
In restoring hotwheels windshields we use Pledge Future Shine floor polish to clear up small scratches and discoloring.
There are so many different variations of this technique I was honestly just interested to see Adam try it. Some people say temperature, others UV light. It's also important to note that many reports of plastics re-yellowing at an accelerated rate means for some materials it's a purely cosmetic process that has to be redone. I think its still a new enough technique that there isn't a lot of long term evidence floating around but I'd love to know more about the chemical reasons this seems to work.
303 Aerospace Protectant or some other kind of dressing (potentially even Armor-All if you want it to be shiny, but I wouldn't use it) will keep it protected from yellowing as quickly. There are a couple of chemical reactions happening in plastics that make it yellow, and I think that people are in general thinking that yellowing is due to UV when it's due to UV and oxidation. A good protectant/dressing will help against both causes, but moreso UV exposure than oxidation.
you just need uv light to activate it, the way adam did it was completely useless, you can use sunlight or an uv lamp setup, what a missed opportunity, it really works like magic
It works only when exposed to UV light. Key is to have very even light and solution distribution to avoid uneven bleaching. However i dont know if it will work on clear acrylics as the yellowing will in this case go thru out the entire thickness of material.
Awesome video Adam sir thank you for sharing sir.
I've used peroxide mixes on hundreds of pieces of plastic of varying condition and ages and tried just about everything. Heat alone works best in my experience, no UV needed. Pop the bath in your lab oven at 130F and give it between 8 hours to 3 days. Agitate regularly since the reaction will produce bubbles. 12% peroxide is on the strong side, especially for transparent plastic. Dilute it to around 6% and give it a shot, increase concentration as needed.
And a black light...... Dont forget the black light its what helps to work..... I use it to restore yellowed game cases....
There was a headlight restoration kit that we used at Monro muffler, it was a sand and buff up to like 2000grit with a final liquid component that was wiped on with of all things a "Mr eraser" sponge.
Was like magic. End of sanding the lens would be that same frosted look, but you hit it with that liquid and boom like a new perfectly smooth clear lens. Set the uv light on it to cure it or set in the sun on a warm day and good for years.
Welcome to the weird and wonderful world of Retrobriting!
Incidentally, short-wave UV is what is usually needed for hydrogen peroxide to de-yellow plastic.
*LGR and 8 Bit Guy have entered the retrobright chat*
Why oh why did I just spend 20 minutes watching a person I'll never meet polish a piece of plastic I'll never own, using equipment and a workshop far, far beyond my own? There is some magic here I don't understand.
Paper towels can cause scratching on soft plastic. Microfiber towels are best for polishing.
A possible alt solution... It used to be common (in my grandparents time) to add just a bit of blueing dye to white laundry, especially in urban areas where the city water was discolored. Because the color blue is on the opposite side of the color wheel from yellow it counter-balances out the yellow to make a pure white. (Note: This is why so many whitening mouthwashes are blue). So… maybe a very light blue tinted wash might decrease the yellowing? Def something to test before applying to your expensive NAGRA cover.
I thought you said you researched the internet Adam!? Uv lights! Restoration videos are some of my favorite
Both heat and UV light are king as a combination to remove the yellow, the best thing I found that works very well, is to warm up your hydrogen peroxide, then get a black pot or pan, put your yellow part into the pan, then poor in your warm hydrogen peroxide, then set the pot outside in an area that gets full sun, after that day, remove your item and rinse it off, the results are amazing. 🤠👍⭐⭐⭐⭐⭐
The process you did in this video is called Retrobright, which is commonly used to restore "yellowed" parts in old ABS plastic if I am not mistaken.
But I seems to recall that this process is used in conjunction with a UV light source.
It's the same process we use on collectable toys that have yellowed and it sometimes takes a couple of days to really clear it up... depends on your peroxide strength and also put it in sunlight or under UV lights. Will super power the process to only a few hours
I too also use Novus 2 Fine Scratch Remover.. Great stuff!!! works great for headlights.
Wow. What a beautiful peice!
"These aren't chiral, are they?" I love the use of chemistry terms in engineering!
Man my face when you said holy shit cause I'm listening out loud at work. Thankfully no clients are around 🤣😂
The internet said something that wasn't quite right? Inconceivable!
I got the Proxxon rotary tool that you recommended before and I use it all the time now.
Now that you've cleaned up the plastic, you should spray it with some high quality 2K clear coat to protect it from further damage. It will also fill in the tiny scratches left.
"I don't know why it took me so long to get an electric polisher." Well, you just sold me. Time to order one before I get another scratch removing job.
Mr. Savage...I'm surprised that you are using paper towels on plastic. Interesting. Love all that you do, sir.
My dad loved stuff like this.
While I have no interest in the Nagra, I appreciate its design, aesthetic, and the joy Adam has in it. Great video! 👍🏻Reminds me of something that should be on the Nostromo 😄. Doesn't this method also work on Lego bricks that have yellowed?
Yes.It works quite well. On all plastics
I de-yellowed my 1986 Heathkit Hero 2000 robot, which is still up and running. Back in 1986, they were selling for $4,500, unless you chose to purchase it in kit form. Hydrogen peroxide, a big helper.
The very machine used to record the Beatles soundtrack on the Get Back Sessions. Nagra Reel-to-Reel tape recorders are one of the gold standards for High Fidelity which is why they fetch $1200-2000 for these machines.
This is a great technique for anyone who wants to restore an old Turntable dust cover. Yeah!
Adam,
Are you planning to ever start filming in 4k? It seems like tested is one of the only channels still uploading in only 1080p.
Shake the Novus well! Once had a bottle that settled and the grit fell to the bottom. You can imagine my surprise
Novus polish is amazing stuff. I keep 3-2-1 on hand for model car windshields and airplane canopies.
The reason for the yellowing of plastics over time is the addition of bromine to the plastic as a fire retardant during manufacturing. The Peroxide when combined with UV light will greatly reduce the yellowing but be careful of leaving it for too long. It could cause the plastic to become more brittle
Back in my car racing days, we used Lexan for windshields. After 3 or 4 races it would get sand blasted with some small scratches. We used a tube of cheap toothpaste with a buffer then a couple coats of Rain X to get the really small stuff. It worked great and was pretty cheap.
I don’t known how you work with these fragile, rare/one of a kind objects like this. I was wincing every time you even set it down on the bench
From what I have seen, you need UV light as an activator for the hydrogen peroxide.
Watching on my TV. Hopped to the phone to mention UV light but see the community has it covered. People use peroxide gel also
excellent work - however, one additional step - think fiber-optics - if you are able to get the cut edges of the plastic cleaned up as well, the color will look a lot less yellow. crystal clear plastic takes whatever color VERY personally
Interesting idea, that would make sense if the edges were left I worked. As obsessively as Adam went at this, I have to believe they got plenty of love too.
@@Spacemanspiff808 oh i agree - but you can see the edges near the end of the video being left yellowed, hence my comment
If you were going to make a copy, how would you go about it? 2-piece silicone mold with epoxy injection? Mold the inside for a vacuum-forming buck? Would vacuum formed plastic be stiff enough to be a cover? Both would be fun to watch!
Vacuum forming is likely how it was made in the first place.
9:30 It looks like something that would be easy enough to make a vacuum forming mold for a new part though... store the old one safely and enjoy the reproduction.
You know it's serious when Adam swears. That is a night and day difference, jeez
I was taught to never use anything that used to be a tree to polish plastics. I've seen the result, it can make things hazy. I use the Novus products on my motorcycle windshields, I've used it for years. I use micro fiber cloths and final rinse with alcohol to remove the film the compound leaves before I polish it. As others have said, use UV light with the peroxide and let it soak for at least 24 hrs. For absolute best results you can finish with a clear spray paint with uv protection and it will never yellow again.
The original process that got talked about back in the day was retrobright which added more than just h2o2 and included UV. Look it up on Wikipedia and then for the original sources
*ADAM IF YOU MANAGE TO READ THIS USEFULL INFO, I'M HOPING IT HELPS*
Toyota has these little headlight coating kits used by the dealer, it's pretty cheap and you can by it from them. Comes with this purple liquid that you rub after final polishing.
I used it on some plexiglass and lexan in a couple of projects and it makes it 10x better as well as remove some outer yellowing.
as for the yellowing inside the plastic, I don't think you can remove that entirely.
Also if you plan on making a copy with vacuum forming I would love to watch that.
Thank you and have a nice day.
Meguiar's various Mirror Glazes for plastics have always worked well for me.
8-bit Guy has some really good videos on restoring old plastics.
Kinda weird that Adam said he looked at posts online about using hydrogen peroxide for de-yellowing, but those posts DIDN'T mention UV light? That seems odd. That's, like, the other half of the retro-brighting process.
That's UV damage. Use a car headlight restorer kit (Turtle Wax or Meguiars). They have a sealant which keeps it from getting worse.
The 8-Bit Guy uses peroxide and UV (from sunlight). Works well. Also, paper towels are incredibly abrasive. Use cloth (microfibre) instead.