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I've been seeing all these videos about using a heat gun to restore faded plastics, especially exterior black trim pieces.

  1. How exactly does this work? Is the plastic melting again on the surface? Is some oil/liquid oozing out from the interior of the plastic? Is deeper pigment leaching back to the surface?
  2. How long will this treatment last before fading returns?

Overall the process does appear to work, but the videos don't really offer any timeline for the expected duration of success.

Here's some of the videos I watched demonstrating this process:

Faded Plastics back to black with a Heat Gun [link]

This fella uses a wagner heat gun he bought for $20 and mentions the process running 10-15 minutes. Says the pigments of the plastic rise up to the faded pieces. Claims the fix lasts at least a month from his last update.

There was an interesting comment left on this video which explains:

when the sun heats the plastic, it attracts moisture from the air; as the plastic cools, the moisture gets trapped in the closed cells. It shows up as a cloudy grey on the bumper. The heat gun opens up the cells and allows the moisture to escape. Tougher areas means deeper trapped moisture. This technique will also work on tea-cup stains on varnished pianos...coffee tables etc.

before and after from heat gun treatment

How to Restore Faded Plastic/Trim | Easy - Automotive | Amazing Results | Heat Gun [link]

Treats a few body parts for his motorcycle. treated and untreated motorcycle body part treated and untreated motorcycle body part

Heating plastics to bring back BLACK [link]

Restores the plastic parts at the top of the car hood/bottom of the windshield. Claims process works by "bringing up the natural oils" of the plastic to restore its color. Follows up heat treatment with automatic transmission oil to restore shine.

treated and untreated windshield wiper hood plastic

Restoring Jeep Cherokee Fender Flares with a Heat gun [link]

Mentions using heat gun on high setting. Gives warning when working near the gas cap. faded unfaded Jeep Cherokee fender flare

How to Restore Faded Plastic with Heat... Permanently [link]

This guy restores some floor car seat rail covers. His technique was to be 3 inches away from part on the high heat setting. Says his treatment has lasted up to a year for that part, which is in the interior of the vehicle. Follows up by treating parts with Mothers Back to Black Trim & Plastic Restorer polish.

floor trim, car seat rail covers

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    The faded surface is actually rough with minute pits and scratches. I think the heat melts the rough fibrous surface. I have used this technique on a much smaller scale for electronics work. If you want to try it, get a scrap piece of automotive plastic and experiment. Wear cotton gloves.
    – John Canon
    Commented Dec 16, 2019 at 2:05

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How exactly does this work? You're heating the plastic up to what's called its glass-transition temperature. I'm not a mechanical engineer, but my understanding is that the crystal structure of the molecules (previously damaged by UV radiation) starts to break and molecules move around again with one another just a tiny bit.

How long will this treatment last before fading returns? Based on the sample set of the one car I've seen this performed on, about a year in Texas sun. It's a bit like "restoring" headlights.

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I found a lot of conflicting information with regard to what exactly heating the plastic is doing. Some say releasing oils, other leaching pigment, releasing moisture, melting, and on and on. Seems there hasn't been a truly definitive answer from science yet.

I dont believe its glass transition because that has to do with rigidity vs pliability for specific types of plastics. Personally, I'm more inclined to the idea that its slightly melting the plastic or pulling something out. The one piece of information I've seen throughout most of the discussions on the subject is that it can only be done a few time (which leads me to believe something is being lost or consumed by heating the plastic).

As far as how long it lasts, that seems to be widely variable (possibly due to specific plastics chemical makeup, and definitely due to environment and exposure), from as little as weeks, to as much as years.

My opinion and limited experience says it's better to regularly use a rejuvenation product than attempt to heat treat it. Brittleness is not really a good side effect, and you can avoid that by proper care.

That said, if your situation is just to make something look a bit better once, sounds fine to me, but I still think another product would be better. The vast majority of the time, it's all about regular care and maintenance.

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  • Except those explanations have very little scientific backing. There's nothing you can wipe up after this, so oils (why would there be any?) and pigment don't add up. "Slighly melting" and heating to glass temperature are the same thing. Tg is right when the material becomes pliable (and shiny, like glass) and is headed toward "melting".
    – Drewster
    Commented Dec 17, 2019 at 2:19
  • So first Tg and melting are similar, just one applies to crystalline polymers (melting) and the other applies to amorphous polymers (Tg). I can admit that o dont know enough about specific polymers to say which is which, but that's another reason to ahy away from heating. Further Tg doesnt necessarily correlate to shineiness from what I understand, whereas melting does because its transcending to liquid state (at least briefly). I'll update a few links.
    – kyle_engineer
    Commented Dec 17, 2019 at 3:15
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I am trying this for the first time on an atv that is faded red Using a blow torch i found that heating it does bring the color back but then it fades back within minutes. So then i heated it to get the glossy red back and about a minute later i applied car wax. And it stayed glossy red dont know how long it would last but it looks good overall.

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