Those spots on old instrument clusters....

[Tom]

Admittedly, you pretty much need to have the clear lens removed to do this, but it does work like a charm. As my 911-style gauge kit nears completion, I thought this would be worth sharing....

[Zirconocene]

Very interesting! 2 questions:

- Do they stay gone? What's the longest lived part you have after this repair?
- Do you think that an oven would work? It may be easier to control the temperature that way and avoid warping due to localized heat spots.

Thanks for sharing, this is great and good food for thought about what's happening.

Cheers

[Tom]

Very interesting! 2 questions:

- Do they stay gone? What's the longest lived part you have after this repair?
- Do you think that an oven would work? It may be easier to control the temperature that way and avoid warping due to localized heat spots.

Thanks for sharing, this is great and good food for thought about what's happening.

Cheers

I did this as part of my 911-style gauge project, so it's been only a month or so. Honestly, it didn't occur to me that they might come back. My thought was that I'm basically melting the surface of the plastic so it can reflow and re-crystalize, making it good as new. But I suppose if part of the issue is the plastic just drying out, maybe it just spreads the dry spot over a larger area, encouraging it to come back. Now I need to go back and look at the parts I did last month...

Maybe someone with a strong chemistry background like @Larry C could offer a more informed opinion... They didn't offer a polymer science class in law school.

I'd be worried about putting parts in the oven. As you can see in the video, you need to keep heat on it quite a while, so I'm thinking the spots need to get plenty hot to reflow back their original color. Not sure you could get away with heating the whole part to the needed temps without melting it.... I guess there's exactly one way to find out though...

[Larry C]

@Tom Unfortunately, my inorganic and organic chemistry classes were 45 years ago and I don’t think we discussed polymers. I think it’s more of a physics issue. Nevertheless, let me see what I can find out.

[Larry C]

This may explain what causes white spots on plastic. Now I need to see if there is a remedy.

https://physics.stackexchange.com/quest ... -of-stress

[Larry C]

I think @Tom is on the right track. It will take a bit of time to see if the spots come back. I’m thinking they won’t.

https://www.bing.com/videos/riverview/r ... &FORM=VIRE

[ROB III]

Using heat on sun faded/oxidized black plastic pops up on YouTube, primarily for black trim (such as the trim around windows) and bumpers. Looking further into the heat method seems unclear from most video's on longevity and if it has a negative impact on interior trim. I haven't seen much on my 89 951, but I've used some Swissvax products on the trim around my hatch which did work, but it is not a cure all permanent resolution to the issue as some fading seemed to return without reapplication..
Here are two sites that recognize the heat process but don't necessarily recommend heat as a cure-all.

https://www.autoobsessed.com/pages/how- ... astic-trim
https://thedreamyway.com/restoring-vehi ... on-finish/

A paint may be the most enduring material as some plastics (such as a dash) from OEM are painted to meet color matching requirements between trim items, because even the preferred treatment called out

[Tom]

One thing I can't tell is whether the spots that appear in the binnacle are the same as the general greying of exterior black plastic trim. Old binnacles are a bit greyer than fresh ones, but they don't seem to fade to grey like exterior trim. The spots almost look like mold, but the plastic is actually discoloring. I have tried the 'lotion' style plastic treatments, which don't do much on the spots. Those two sites both promote Solution Finish, which appears to be a dye-based trim product. I've used the Forever Black stuff on exterior trim -- which is also dye-based treatment and looks great. Maybe I'll see if I still have some of that and give it a try. It lasts maybe a year on the exterior parts, but maybe inside the cabin it would last longer? After poking around, looks like most places frown on heat as a solution, at least for grey exterior trim, but then again most of them are selling something. Another option might just be flat black paint, especially since the binnacle doesn't need to match anything per se. I'll keep at it...

[ROB III]

Tom, Good point..... I hadn't considered the sales perspective. I'm more a proponent of a high quality non gloss black paint myself for this specific application.

[Larry C]

I’m no expert regarding discoloration of plastic / polymers but it seems that we should differentiate between discoloration due to oxidation versus stress related discoloration that’s a consequence of a change in light refraction.