I loaned my iBook G4 to a friend, and it came back with cosmetic damage to the case bottom.

Although he swears the deuced Mac(hina) sat on a dry towel the entire time he had it, it looks like some liquid got to it and eroded the shiny finish, leaving it kinda lightly textured/striated and, although still smooth to the touch, not "sticky" like the factory finish. (I can't post photos, because the damage is waaay too subtle to be captured by my camera.)

I don't really care about the damage, which is 100% cosmetic, but I want to sell the computer, and I'd like to be able to describe its condition accurately, so I figured I'd see if anybody knows what the "solvent" might have been (to save me from emptying my closets and possibly inflicting further damage through my investigative efforts).

Considering the household in which the iBook was, I have to consider alcohol a likely candidate.

Thanks.

Try to find out what type of plastic the case is made of, and whether there is any surface layer applied to the plastic after it is molded. If the case is simply molded plastic, minor surface flaws can be polished out using Meguiars plastic polish. The damage could be abrasive rather than from a solvent.

Here are some notes from the old forums (I fixed the URL):

From: http://www.macfixit.com/ultimate/Forum1/HTML/003845.html

posted 04-16-2000 07:31 PM The Meguiar's plastic polish has a new part number and packaging. The old designation was MGH-10 Mirror Glaze Plastic Polish, which meets specs MIL-C-5547 and MIL-C-18767A(ASG). This is to be the product shown at http://www.meguiarsdirect.com/detail/MEG+M1008 . The part number is 1008. (for #10, 8 ounces)

You do not need to polish first with M-1708 unless the scratch is really rough. Meguiar’s M-1008 and M-1708 are what are called chemical rather than physical abrasives. They are claimed to have no effective grit size, and to work by chemically breaking down a microscopically-thin layer of plastic. Tech support did not explain why rubbing is still necessary (Nov. 24, 2000).

Although alcohol is a good way to clean oils and waxes from the plastic surface, unless it is ignited it is unlikely to do any detectible damage. Acetone (fingernail polish remover), alkaline substances such as powdered household cleansers and Drano, possibly even a towel washed in a really harsh detergent and not well rinsed, sand, are all possibilities.

Rather than trying to perform forensic analysis to determine the causal agent could you simply describe the surface as "slightly deglazed"?

According to the text at the top of:

http://alatest.com/reviews/laptop-reviews/apple-ibook-g4/po3-1379,30/

the case is made of polycarbonate.

Polycarbonate is a tough plastic, but its kyrponite is ammonia.

I once spent a lot of time polishing the mold marks from a G4 Cube case with Meguiars plastic polish. The result was a case that was better than a new one. The Cube had to be sent back to Apple for a repair. I enclosed a letter asking them to be careful with the case. I got back a computer with a new case, with mold lines, and a form letter stating that all components of my G4 Cube had been updated to current specifications.

> [...] could you simply describe the surface as "slightly deglazed"?

Thanks for suggesting the language; it may be my only option, although I'd really like to be less ambiguous.

I guess the mold lines are a design feature.

As respects Meguiar's Polishes, their website mentions clear plastics any number of times but says nothing about opaque plastics, although I guess your experience with your Cube is telling.

On the other hand, though, I found Polishing polycarbonate, which is less than heartening (but I might give Turtle Wax a go, simply because it's readily available).

Thanks for your input.

Artie,

You are welcome.

I now recall that I did some of the initial polishing of the Cube with Wenol metal polish, which cut the plastic faster. The final pass was with Meguiars.

if its lost its shine then its probably been chemically pitted. (at a microscopic level) Plastic polish is your best bet to recover the shine. My mom uses Novus on her acrylic chairs. I can't vouch for its effectiveness on polycarbonate, it's most commonly used to polish acrylic.

I have seen Novus at good art supplies stores. It is odd that the Novus site does not have a conspicuous mention of polycarbonate.

Novus 3 cannot be used on polycarbonate:

http://www.modernplastics.com/april05/wdnovus.html

Hello MicroMatTech3,


When I access that link, I am taken to the first page of
http://reviews.cnet.com/macfixit/?tag=mfiredir

I am not clear if that page is the reference you intended.

Dianne,

I should have made it clear that it was the Meguiars URL, not the MacFixIt Forums URL, that I fixed.

but novice 1 and 2 seem to be ok for it. #3 must be too abrasive?

Novus 3 contains dipropylene glycol monomethyl ether, according to the MSDS:

http://www.novuspolish.com/msds.html

Dipropylene glycol monomethyl ether is used as a solvent in the dying of polycarbonate:

http://www.patentgenius.com/patent/5453100.html

Wow... Complicated issue!!!

The Woz iBook states that


That suggests that my iBook's lost finish/gloss is the result of a chemical reaction that scoured off its polycarbonate coating and that the best polishing may do is impart some shine to the under-case.

It occurred to me to call the issue in to AppleCare as affecting my (covered) MacBook (which appears to be made of the exact same material as the iBook), and although the tech's best suggestion was, understandably, to bring it to a Genius for a look-see, he tended towards the same thought I expressed in the previous paragraph.

I also took a look at recent eBay sales of iBooks similar to mine to try to get an idea of how much I might realize from a sale and found that it wasn't likely to be enough to justify my getting involved with ordering and testing expensive (not necessarily, but after delivery...) polishes, so I've decided to give the Turtle Wax suggestion a go...cheap, and available pretty much right around the corner.

More to come...

Thanks to everybody who's contributed input.

I just received this response to an inquiry I posted to NOVUS Polishes:


I guess that's option #2, after Turtle Wax, if I can locate a bottle at reasonable cost.

Hmmm... This,


from the response I received from NOVUS Polishes, either contradicts that or indicates lack of knowledge on the writer's part.

I'm nowhere near a chemist and can't make any kind of determination from reading the patent, nor do I care to question the writer's knowledge of a product he represents, but


from this doc suggests that abrasiveness, as specified by the writer (and speculated by V1), may, in fact, be the correct reason, not DPGM's solvency.

Edit: I'm still waiting for Turtle Wax to advise me about which, if any, of its products is suitable for polishing polycarbonate

Update... On a lark, I spent a coupl'a minutes the other night buffing my MacBook (also polycarbonate) with a relatively smooth-textured cotton handkerchief, and, lo and behold, the scratches in its top-case (the worst of which I'm pretty sure were inflicted by the Genius Bar) began smoothing out.

Note that this refers to surface scratches, as opposed to the dissolved finish that instigated this thread, but it is worth noting, all the same.