Removing yellowing from plastics - Part 2

[Terry Yager]

Use the gloves<snip>

Geeze, even a hairdresser knows that (for sure)...

--T

[krye]

What's is creating the heat? The bulbs? I susppect that's the source.
If so, I'd move the bulbs farther away - the process needs the UV from the bulbs, not the heat.
Maybe Merlin could comment on whether or not the corn startch might create heat due to some reaction.

I can tell you exactly what happens when it gets on your hands - it burns, and after ten seconds your skin turns white. Use the gloves and some goggles/glasses. If it does that to your hands, imagine what it would do to your eyes if you got some splashed in them.

Yes, I know. I had goggles and gloves on the whole time. 30% H2O2 is pretty nasty stuff. <sarcasm>Terry, thanks for the great contribution to the thread.</sarcasm>

As far as the heat goes, it's not like the bulbs are warming up the solution. The solution is actually generating its own heat. The bulbs aren't that hot to the touch. There is a reaction happening. I remember this being mentioned previously in the thread somewhere. If not here, then here or here.

It's the next morning and this stuff is now as thick as it can get. I washed it off with the garden hose. It was almost like the frosting you'd get on a donut. Actually, it looks like jizz. Anyway, it's drying outside right now. One thing I did notice is that the solution ate away the paint on the Apple logo. So I am kind of bummed about that. Maybe I can repaint it. I'll post more before/after pictures once I have it dried off.

[Lorne]

You need to put something on some of the painted parts or some kinds of decals. I tried candle wax on metal parts and some stickers. It worked sometimes but not other times. I though of axle grease or something thick but that would withstand the heat generated, but haven't tried it yet. A really good painter's masking tape will work with the paste version of the H2O2. You just have to trim around the part you want to protect (and then cross your fingers).

[Lorne]

I finally found some time to finish my Televideo 925.

I got it back to the black and white that it used to be.

Here's the before and after photos:

TV925 keyboard - before.jpg
Televideo 925 - keyboard done.jpg
Televideo 925 - before.jpg
TV 925 done.jpg

[krye]

@Lorne: Looks awesome.

The LC III is done too. Looks like I left it in the sauce for too long. I think I over cooked it. There is no trace of yellow, but the white is a little uneven and even looks a little "frosty" in some places. I knew I should have washed it off at midnight last night, but I got into other stuff and couldn't be bothered. The Apple logo too is toast.

If anything, this serves as a good trial run for the Mac Plus and Mac SE that I'm waiting for. (I bought them off eBay last week. Still waiting for them to be delivered.)

Before:


After:


Before:


After:


Apple collectors be warned. The Apple logo does not survive this process. I'll have to find a way to mask it off in the future. Maybe hot glue?
Before:


After:

[Lorne]

Those are some pretty nice results.
What a difference !

I've found that while the paste solution works well for vertical or very large surfaces, the original liquid solution works best for the most even results.
It's either that, or you need to remove and reapply the paste a couple of times during the process to get more even results.

I toasted an Altos label, which are a lot harder to come by than an apple logo.
I wouldn't worry about it - it still looks a whole lot better than it did.

[krye]

@lorne: Totally.

Anyway, I figured out a work around for the Apple logo. I hope they are like this on all models. I noticed a hole in the case behind the logo. I stuck a pin in there and pop! The logo came out.

[Merlin]

@ Krye

Nice results you got there! Regarding the corn starch, that won't be generating the heat, the heat is due to the TAED in the 'Oxy' catalysing the peroxide.

My recommendation to you if you are getting so much heat is to dilute the peroxide back. Yes, it takes a bit longer, but the heat and possible distortion of parts is much reduced; it's also a lot safer to work with as well.

I'm glad the corn starch worked out as a gelling agent though, it was a bit of an educated guess and isn't that far off the xanthan gum method. I would suggest that you make the gel beforehand with the corn starch (you can store it this way) and only activate it with the 'Oxy' when you need to use it. The gel will be stable on it's own without the 'Oxy'.

[Lorne]

And I think Merlin would agree that if you premix it, and store it, you should store it in a container that won't see the light. I'm surprised that your H2O2 came in a clear plastic bottle. Mine came in white plastic bottles, so the UV won't degrade the H2O2. You should probably store it somewhere dark, like in a pantry.

[krye]

Thanks for the comments. I think I will definitely tone down the solution next time. It's too white! Almost "ashy". I left it in too long. Next time I'll try maybe 4 hours, wash it off, and then have a look.

Before:


After:


I just have to do the monitor, but I need a break.