So I've heard alot about acrylic not yellowing. But the security light fixture I just pulled down (powerlight I believe) has an acrylic refractor and it has slight yellowing.... I assume a polycarbonate refractor of this age woulda been literal dust!

I heard of methods of removing yellowing such as soaking plastics in hydrogen peroxide or creams containing it. Is this possible on an acrylic refractor to restore it to its former beauty or will it yellow back up after a few months?

So I've heard alot about acrylic not yellowing. But the security light fixture I just pulled down (powerlight I believe) has an acrylic refractor and it has slight yellowing.... I assume a polycarbonate refractor of this age woulda been literal dust!

I heard of methods of removing yellowing such as soaking plastics in hydrogen peroxide or creams containing it. Is this possible on an acrylic refractor to restore it to its former beauty or will it yellow back up after a few months?

I believe you could use the method used by mechanics to fix yellowed headlights. it may be worth a try even though headlights are most likely a different type of plastic

https://e3sparkplugs.com/blog/yellowed-headlights-three-ways-shine-em/

Will not work. The yellowing is internal as well.

oh ok. didn't think about that. makes sense though.

I think they are simply not pure PMMA, but have some additives for whatever reasons..

The yellowing is a sort of corrosion as far as i know, it needs the UV and oxygen from the air. So i cant see how it would happen deep inside the material, unless there are micro cracks...

I had faced one other problem with PMMA. The other day i saved a big stock of Italian posttops from the 90s, basically some assembly with vertical Merc lamp and a huge PMMA cube that inserts over it. They appear a little milky but the problem with them is they are brittle beyond any reason. You pick them up a little roughly and they just crush and crumble. Two cubes look a little different from the others (slightly less rounded, definitely different batch) and they are good as new, not milky at all and appear as strong as should be

I use Autosol (any good metal polish) to clean up my bowls, if that doesn't work then you're kind stuffed maybe try and use the retr0brite (hydrogen peroxide). results may vary.

I was cleaning up the bowl for my Raymond SL65 it made the bowl nice and smooth but didn't remove much of the yellowing, it wasn't that bad, I was happy with the results. you can use Brasso because that is the only thing it is good for.

I use Autosol (any good metal polish) to clean up my bowls, if that doesn't work then you're kind stuffed maybe try and use the retr0brite (hydrogen peroxide). results may vary.

I was cleaning up the bowl for my Raymond SL65 it made the bowl nice and smooth but didn't remove much of the yellowing, it wasn't that bad, I was happy with the results. you can use Brasso because that is the only thing it is good for.

I've used Brasso to quite good effect on the casting of our Beta 5 lantern, that I'm going to be converting into a table lamp.
Autosol might be a better option, as I can use my Dremel rotary tool. 

I use Autosol (any good metal polish) to clean up my bowls, if that doesn't work then you're kind stuffed maybe try and use the retr0brite (hydrogen peroxide). results may vary.

I was cleaning up the bowl for my Raymond SL65 it made the bowl nice and smooth but didn't remove much of the yellowing, it wasn't that bad, I was happy with the results. you can use Brasso because that is the only thing it is good for.

I've used Autosol several of my yellowed lanterns too. As you said it makes the plastic nice and smooth/shiny but the yellow colour is still there, which is ok with a sodium lamp as the light is orange anyway but with a mercury or fluorescent lamp it affects the light colour.

Ive been able to reduce yellow on some old wall pack policarb covers by scrubbing the cover real good with baking soda and isopropyl alcohol which turns the paste yellow. It reduces the yellow because it takes of a coating that has built up. It doesn't remove all the yellow because there is yellow inside the plastic also.

After the baking soda and alcohol scrub, I wash it off and let dry. Then I wipe on a really thin helping of mineral oil on the plastic with a soft cloth just to polish it up. Needs to be so thin so it isn't greasy and only on the outside, not sure if the heat from a lamp will affect it so I didn't coat the inside part.

Please keep in mind that thats what I've done and it likely isn't 100% and it may not last but its something. Scrubbing with baking soda may cause abrasions or take off the shiny look. It didnt in my case but try at your own risk

We'll have to try that ourselves, I have ordered a 2.5kg tub of Bicarbonate of soda and we've got a 500ml bottle of isopropyl.

So we're all set for a cleaning spree.  

We do need to get the mineral oil though.

It helps to get a good sponge as well. The kind with the abrasive backs are what I used, but i didnt use the abrasive back part, just the normal sponge side. Used that because they are easier to hold and apply pressure if needed versus a wimpy standard sponge.  To get into the little nooks and crannies of the cover I used an old tooth brush with a bend back brush head.

I forgot to add that after I was done with the soda scrub I rinsed off using some dish soap and used a clean sponge and the toothbrush after cleaning it off.

Hopefully this helps you and best of luck it may not be for everyone

@ Lightingguy:

Thanks for the advice.