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The truth about Retr0brite – busting myths with science…

vol.2 said:
This jives generally with what I would assume. I've also seen antennae parts on a roof break down, and I assume UV is an issue. I suppose from that, I would say that the UV part of the process can indeed harm the plastic, and could be an issue if it is already substantially damaged.

So if UV is involved in the retrobrighting process, then it is making plastic brittle, and that's not actually a myth. I suppose from the video, it's not necessary and you can just use heat and chemicals with no lights.
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Keep in mind that the UVB is filtered out by window glass, most of the UVA gets though though. You can't get a sunburn sitting in front of a window. The UVA is what causes the yellowing. This process takes years. The time spent to Retr0Brite or SunBrite is insignificant w.r.t. the years/decades it took to become yellow. Sun bleaching exposes the plastic to the the UVB as well thus you see the bleaching process.

Both yellowing and whitening the plastic has some small effect on it. Think of it like sanding a table top to refinish it. You are altering the structural integrity of the wood but it is insignificant. If the original damage to the table top is severe and it continues to crumble when sanding we can't blame the damage on the sanding, the table was already damaged.
 
Jeff_Birt said:
Keep in mind that the UVB is filtered out by window glass, most of the UVA gets though though. You can't get a sunburn sitting in front of a window. The UVA is what causes the yellowing. This process takes years. The time spent to Retr0Brite or SunBrite is insignificant w.r.t. the years/decades it took to become yellow. Sun bleaching exposes the plastic to the the UVB as well thus you see the bleaching process.

Both yellowing and whitening the plastic has some small effect on it. Think of it like sanding a table top to refinish it. You are altering the structural integrity of the wood but it is insignificant. If the original damage to the table top is severe and it continues to crumble when sanding we can't blame the damage on the sanding, the table was already damaged.
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thanks for clearing that up, that was exactly the question I had after watching your video (UV A vs B).
 
It would be interesting to write to some of the traditional museum conservators and see what they know about Retrobright. After all, their job depends on knowing such stuff.
 
There was a report from a museum (I can't find it at the moment) that attempted retrobrite on a sample piece and concluded that, while the results are promising, there are new microfissures visible under magnification after the process, and that the long-term effect of that is unknown. As such, they advised to not attempt the process.

Edit: Found it: http://aktuelbevaring.natmus.dk/afrensning-af-plast-med-retrobright.html
 
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Trixter said:
There was a report from a museum (I can't find it at the moment) that attempted retrobrite on a sample piece and concluded that, while the results are promising, there are new microfissures visible under magnification after the process, and that the long-term effect of that is unknown. As such, they advised to not attempt the process.
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I mean, Chuck linked to that earlier in the thread unless you’re talking about a completely different one. And, as has been pointed out, they weren’t using ABS, so not really relevant to us.
 
It is good to see some actual science going on. If I had access to a large stock of disposable yellowed plastic, I would at least try some simple tests regarding time/light/heat/peroxide percent/brittleness/whiting depth and such.

I thought the entire point of genuine Retrobrite was to add something to that would help prevent the plastic becoming brittle from the process.

Also, just throwing this out here - One method that has worked well for me on some kinds of surfaces to reduce the peroxide used, rather than a paste, I just take facial tissue, break it up in to each of its two thin plys, lay the tissue on the surface, then drip some common 3% peroxide on it. That does require periodic attention so it does not dry out. Perhaps ideally also moving or reapplying tissue at some point to keep whiting even, but I have not had any issues with that, perhaps because it is slower with the 3% so it stays even. Really handy for lightning up a floppy drive that I couldn't get apart, just drip a little on the front, face it toward the sun, add a few drops every now and then, and by the end of the day it looked much nicer.
 
Using vinyl paint that soaks into the plastic would protect the object while making it look better.

My Amiga 4000's front plastic is very orange in color (at least it is uniform in yellowing). If I was going to do anything to it it would be painted.

I have never heard of anybody doing a retrobright that didn't yellow again in a few years. Maybe some kind of spray on clear coating would help block UV rays.
 
Trixter said:
There was a report from a museum (I can't find it at the moment) that attempted retrobrite on a sample piece and concluded that, while the results are promising, there are new microfissures visible under magnification after the process, and that the long-term effect of that is unknown. As such, they advised to not attempt the process.

Edit: Found it: http://aktuelbevaring.natmus.dk/afre...trobright.html
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I'm reading the Google Translate version of that article, so I can't be certain, but it looks like the article is saying that their results are only about certain types of plastic: "polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyethylene, polystyrene and cellulose acetate". The experiments appear not to have been carried out on ABS plastic, which seems to be the common plastic for computer cases.

Edited to add: The page does say "RetrObright er ikke et produkt som anbefales af konservatorer, da der på nuværende tidspunkt ikke foreligger nogle undersøgelser om gelens virkning på sigt," or as Google Translate would have it in English, "RetrObright is not a product recommended by conservators, as there are currently no studies on the long-term effect of the gel."
 
The other thing about this article is that they don't give details about how they performed the experiment. PVC starts gassing HCl at 70C, and it's crucial to use heat stabilizer additive to maintain some stability. Plastics can all be so different from one another in these regards that exact details are important.
They also don't mention the amount of heat used or if any lights were used, or how long the process took, or the concentrations of chemicals.
 
Trixter said:
There was a report from a museum (I can't find it at the moment) that attempted retrobrite on a sample piece and concluded that, while the results are promising, there are new microfissures visible under magnification after the process, and that the long-term effect of that is unknown. As such, they advised to not attempt the process.

Edit: Found it: http://aktuelbevaring.natmus.dk/afrensning-af-plast-med-retrobright.html
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I read this article and it was interesting. They tested a very small number of plastic materials used an undisclosed laundry detergent as a source of TAED and did not specify the conditions of the experiment, i.e. did they use 6% H202 or 35%, was it room temp or 60C. It really struck me that they tried cellulose acetate (film) which is a very delicate material. I would not expect it to react the same way as ABS, etc.
 
Jeff_Birt said:
I read this article and it was interesting. They tested a very small number of plastic materials used an undisclosed laundry detergent as a source of TAED and did not specify the conditions of the experiment, i.e. did they use 6% H202 or 35%, was it room temp or 60C. It really struck me that they tried cellulose acetate (film) which is a very delicate material. I would not expect it to react the same way as ABS, etc.
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60C is about 140F- not room temp.
 
Obviously the chemistry of aging plastics is complicated. But we all know the discoloring and destructive effects that direct sunlight has on many types of plastics. A bleaching effects on many dye molecules that give colored plastic its color. This is why my restoration method, for white plastic computer panels (not keycaps) leaves plastic in the dark or shade, actually lengthening its life.

I'm not sure all the myths were busted with Science in the video. All good experiments have controls, and for this problem it would require much longer time frame testing and more input from materials Engineers, though specifically it would require before and after high magnification both light and Electron Microscopy of the treated surfaces. And then as mentioned the force tests for any change to how brittle the plastic is.

I would not claim to be an expert in the effects of oxidation & bleaching on plastics (either by chemical or photon treatments) but there is one thing I am fairly confident about; these are both damaging processes to a surface and they break chemical bonds, possibly creating microscopic pits, crevices & cracks. The net effect for some plastics where it is optically visible (not necessarily ABS) but certainly Acrylic, is to start microscopic cracks which can later with force lead to fracture of the material. Most people are familiar with the glistenings that appear in clear acrylic panels after chronic sunlight exposure and in this case they appear within the material as well as on the surface.Clearly the molecular bonds are breaking. Sunlight turns Nylon to powder.

Most surfaces, plastics, metals etc, appear more immune to any kind of surface damage if they are highly polished, presumably one part of this effect is that the surface area is reduced to its minimal value.

For whitening vintage yellowed computer equipment panelwork (excluding keycaps), I have chosen not to use any retrobrite like methods myself, because I discovered a white quick drying highly volatile solvent spray paint (Holts Dupli-color auto spray) that produces a very fine layer,preserving any underling pattern on the plastic's surface. The solvent, briefly before drying (in seconds to minutes) reacts with the plastic surface fusing the paint to it with a molecular bond. This protects the surface from future light expose too.It becomes pretty well impossible to tell that the plastic has had paint applied.

I have mentioned this product on other threads where I used it to restore some IBM5153 and Apple II VDU's. The bond is so good that if one attempts to scratch the plastic the groove created appears to be a groove in solid plastic, there is no layering of the paint, or lifting or flaking. If effectively becomes one with the underlying plastic and simply alters its surface color. This is the only paint I have discovered which behaves this way, due to its solvent reacting with the surface, but not so slowly that it melts away any surface patterns but fast enough to fuse the paint color to the surface. It dries in minutes if a thin layer is applied and is available in many shades for the automotive industry, so its easy to use it to resurface grey or other colored plastics. Nearly every time the issue of "paint" is bought up, remarks are made about it flaking off, obscuring underlying patterned surfaces, but this paint does not behave this way at all. Use the wrong paint and it will probably be a disaster as most speculate.

In any event, I would never use paint on a Keycap. I have found with those a very good result can be obtained, getting rid of most (not all) of the yellowing is simply by polishing the keycap with the fine grade of Novus plastic polish. The surface develops a good gloss which I think helps protect it and the yellowing is reduced. Perhaps with these retrobrite then the Novus to help restore the surface could be a treatment for complete whitening.

I have attached a photo of the restored Apple VDU, but the resolution is limited. But, I'm sure if I handed this to any vintage computer enthusiast and asked, has this VDU been "painted" ? they would look and say no, but it looks brand new.
 

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I'll follow up with a longer missive, but offered as food for thought: Is it the dye/pigment dissolved in the plastic the thing that yellows or is it actually the plastic itself? Dye chemistry is probably as complex as polymer chemistry, particularly with witches' brews like ABS.

I did give a plumber friend a call the other day to ask him about ABS. He deals with a lot of (yech!) wastewater piping and does not recommend ABS for new installations. He stated that the only advantage of it was that it was cheap, but also not pressure-rated. Apparently he's seen his share of failures. He recommends PVC for waste usage--costs more, but in his opinion, worth it.
 
I have had ABS computer case a components go yellow without any exposure to the sun stored in my garage and covered with a heavy blanket.
 
Thanks for the paint suggestion, Hugo. I looked into that paint, but it's not really available in the US. We have plenty of other paint stores here though, so if you could share more information about the exact nature of the paint (type of solvent, type of paint, link to a webpage of the paint you mean), then that would be helpful.

I have a couple of things I might actually try that on because I think they are somewhat damaged by time, and I think that painting them could actually help to strengthen the plastic by filling all the cracks in the surface.
 
Chuck(G) said:
Are we living in the same country? Duplicolor is available through NAPA, Amazon, Advance... After all, it's a US company.
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Not as Hugo, no. In Australia and the UK, Hunts is a major paint company and has their own line of duplicator paints for auto restoration. In the US, we have a commonly available paint called Duplicolor which is made by Shewin Williams.

AFAIK, there is no relation, but I could be wrong.

Also, there are many different varieties of the stuff even in this country depending on what you are painting on. The only info I saw was that it's solvent based.
 
One way to determine similarity is to pick a color and look it up on the SDS for each manufacturer. I suspect that there's more than a little similarity.
 
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