PDA

View Full Version : Why is the inside of a classic Mac painted silver, and is it OK to remove it?



krye
November 11th, 2008, 12:10 PM
OK, I did the peroxide treatment thing (http://www.vintage-computer.com/vcforum/showpost.php?p=76444&postcount=65) to an old Mac SE that I had. The only problem is that the peroxide washed off that metallic coating that is on the inside of the case.

Is that really metal or is it something else? Is it to ground the plastic case, or it is for some sort of insulation or heat transfer? Is it a big deal that 99% of that paint has been removed from my case?

Anyone know?

http://web.mac.com/ryemac3/RyeMAC3/Home/Entries/2008/11/3_Mac_SE_Restoration_files/100_4396.jpg
http://web.mac.com/ryemac3/RyeMAC3/Home/Entries/2008/11/3_Mac_SE_Restoration_files/100_4395.jpg

Terry Yager
November 11th, 2008, 12:21 PM
Probably extra RF shielding, if it's metallic. Might be a little dirtier now, RF noise-wise.

--T

paul
November 11th, 2008, 01:53 PM
Yeah, loss of shielding functionally not a big deal, may emit a bit more RF than FCC allows. Perhaps you can paint it silver to make it at least look original.

krye
November 11th, 2008, 03:14 PM
Ah yes, RF. Didn't think of that. Thanks.

Terry Yager
November 11th, 2008, 03:29 PM
Use metalized paint and shielding functionality will be restored.

--T

krye
November 12th, 2008, 08:27 AM
Use metalized paint and shielding functionality will be restored.

--T

I've been looking around for a "metal" paint. All the paint that I'm finding isn't really metal, it just looks silver, but it's not really metal.

nige the hippy
November 12th, 2008, 09:13 AM
I don't know about where you are, but certainly recently in the UK you could buy nickel spray intended for shielding from RSWWW.COM

Unless you're using it in a hospital or have radio ham neighbours, personally I wouldn't bother re-doing it.

Andrew P.
November 12th, 2008, 09:33 AM
I've been looking around for a "metal" paint. All the paint that I'm finding isn't really metal, it just looks silver, but it's not really metal.

Try to find some "zinc-rich paint". It's usually a petroleum solvent based formulation, and it's used to touch up damage on galvanized steel, such as the welded joints on hand railings, etc. The paint has colloidal zinc metal mixed into it, so once it dries, it can form a conductive surface. You may be able to get it in an aerosol can, although it may only be available from an industrial supplier, not your local hardware store.

I'm not sure how the inside of your computer case was originally coated. Some manufacturers use zinc paint. Others "sputter" the coating on -- the metal is evaporated in an electric arc and sprayed directly onto the plastic surface in a vacuum chamber, leaving a coating of pure metal without organic binders.

Druid6900
November 12th, 2008, 08:35 PM
How about aluminum foil and contact cement? :)

krye
November 13th, 2008, 09:00 AM
Home Depot has some Ralf Lauren interior metal paint in a small 26 oz can. Pretty expensive. It's $18 bucks for a small can and the labels says it causes cancer and other lung illnesses. Kind of scary. Among the ingredients listed are "Trade Secret" and "Unknown concentration". Sounds like pretty nasty stuff. I don't think painting the inside of a computer with it is a good idea. The last thing I need is the paint getting warm and the computer releasing carcinogens into my house.

I think I won't bother re-shielding it. Probably overkill, and was probably just done to keep the FCC happy.

Floppies_only
December 23rd, 2008, 01:25 PM
I don't know about where you are, but certainly recently in the UK you could buy nickel spray intended for shielding from RSWWW.COM

Unless you're using it in a hospital or have radio ham neighbours, personally I wouldn't bother re-doing it.

See if it interferes with an AM radio, an FM radio, and the television, in that order. If you want to use those devices at the same time, repaint. If you live in an apartment, the computer interferes with these items belonging to your neighbors, repaint.

Sean

Floppies_only
December 23rd, 2008, 01:26 PM
I think I won't bother re-shielding it. Probably overkill, and was probably just done to keep the FCC happy.

You can hire a paintshop with somebody who knows how to work with this safely to do it for you.

Sean

tipc
December 24th, 2008, 03:24 PM
"I've been looking around for a "metal" paint. All the paint that I'm finding isn't really metal, it just looks silver, but it's not really metal."

How's about getting some aluminum or steel filings and mixing them up in some paint and just brush it on. Has to be fine stuff though. I couldn't tell you what the ratio of paint/binder to metal should be. But it's not going to harm anything if the ratio is off.

...or you could just bond some aluminum foil to the indside of yer case there dewd.

tipc
December 24th, 2008, 03:28 PM
...or there's lead white artist paint. A company called Rowney sells it (brand available at Michael's and A.C. Moore...don't know where you live though). Takes a long time to dry though, is thick (tough for some people to even get it out of the tube!). Not likely there's enough lead content to provide adequate shielding though. It's merely a pigment that utilizes lead. There's also zinc white, less toxic (but zinc also stays in yer body, galvanized coatings are zinc mainly I think, nasty stuff to breathe and such). Ah but plain old white oil paint is titanium white, so there's no getting away from the metals...