have seenI a number of videos online about how to get yellowed plastic back from yellow to white, especially with people restoring vintage gaming systems and computers. I have read many places that clear plastics would not benefit from this procedure, but I thought I would try anyway. Couldn't hurt!
I started with a simple piece - the yellowed lens from my license plate light.



I bought some peroxide developer on Amazon, though many seem to just run to the local Target or Kohls and visit the hair care section. There are 40's and 50's - I assume that is the strength of the bleaching solution. I also grabbed a UV/blacklight lamp from Amazon. You will also need some foil for reflection, and I used a clear plastic cup as my part holder.



I coated the part in the developer using a small paint brush. You might want to use some gloves and protect the area around your project. Then I set it on some Saran Wrap and wrapped it loosely, such that it wasn't tight, but that the developer wouldn't dry out.



I wrapped the clear cup in foil, set the part in the bottom, and capped with the UV light. Several sites discussing this say that UV is the activator here, and others say that heat is the magic bullet. Either way, this seemed to achieve both.



I set the light on top of the foil wrapped cup such that every side of the piece received UV light.



After an overnight exposure, I pulled the part out of the Saran Wrap and rinsed it off. It's not PERFECT, but it is significantly less yellow than it started out yesterday. So clear parts CAN be affected by the UV/developer combination, and maybe more parts can be saved by doing this simple process - especially where we have parts that aren't replicated.



I understand that some people have used 12% hydrogen peroxide, submerged their plastic parts in that, then exposed the part to UV light/heat for a period of time. It's worth a try as well. As we always say, your mileage may vary. I'm going to try this on some door handles and the sunburned color we get on the old amber ones.

Hope this helps someone

 

We all have formerly clear plastic lenses which have yellowed.

Many thanks for this process.

Chris

 

Thanks for the procedure.👍

 

Interesting thanks , you could start a little side business doing this , can we send you our yellow ones !
To get a new clear one , what about a 3 d printer ?

 

Another submission - I disassembled/destroyed an old window crank, as I had no idea how these were assembled. I don’t think there’s any way to cleanly separate the rubber covering from the rest of the piece. I was just interested in seeing if the bleach and UV would lessen the effects of sunburn browning on these parts, and it does. Here is the same piece, treated as I did the lens above, and exposed to UV light overnight. I’m going to try this method on assembled handles to see if they can be “fixed” without taking them apart.

 

I think the most effective way to recreate a lens or other plastic part is to make a silicone mold and form it that way. The attempts I've made with a 3D printer come out rough - like a coating of sandpaper on the whole piece. Maybe with a super-expensive printer an exact part can be replicated...?

 

One last experiment that really may help when working with darkened/sunburned window cranks. I used 3% hydrogen peroxide and the same foil wrapped clear cup and UV light set up. I simply filled the cup partway and dropped the damaged window crank in the solution. I set the light on top and left it for 24 hours. At the end, I set the whole crank in a warming temperature air fryer at 150° for about 10 minutes to bring back the glossy final appearance. Here are the before and after pics:

on the left is a crank that I consider pretty standard, and maybe I would leave this as is in my car. On the right is a typical sunburned piece. This is the one I chose to restore.



Submerged in 3% hydrogen peroxide (purchased off Amazon)



After 24 hours in solution under UV light




I'm super happy with these results. They also show that the old, burnt ***** do not have to be disassembled in any way to achieve really nice color restoration.

 

Thanks, I've had some luck soaking yellowed plastic in Evaporust but never thought of the window cranks. UV does a good job bleaching but seems to dry out the oils in the plastic.
Dustin

 

When I pulled the crank out of the solution it seemed a little dull and hazy, and before I just let it air dry, I tossed it in the toaster oven for a short warm up. This brought back that shiny finish and for sure the rubber is still pliable.