Painting the aluminum top plate

[mingles]

I'm frustrated. I've been trying to paint the top plate of my Crack for the past few weeks. The paint I'm using is Krylon gloss red. I think it's epoxy-based. Really nasty toxic stuff. The project started out good. I sanded the plate with 220 grit and wiped the surface clean with rubbing alcohol. It looked perfect. I set up a 2'x'2' box to paint inside. I figured it would keep the dust out and contain the spray. I had a fan blowing out the window about 6 feet from the box. Another window was open on the other side of the room for ventilation.

I propped the plate on 1x4s to keep it from sitting on the floor. I shook the can for 2 minutes and sprayed with gentle even sweeps. I let it dry for 15 minutes. The coat was thin, but looked even. I turned the plate around and gave it another sweep. 15 minutes later, it looked great and was fully covered, but I was determined to give it a thick coat, so I gave it another sweep. This time dust settled in a few places near the front. It was very noticeable. I debated living with it because everything else looked so good. Two days later I used some fine steel wool to rub out the imperfections. I went over the whole top to make sure it was smooth. I'm a hopeless perfectionist!! I wiped it clean with rubbing alcohol and let it dry. I made sure the spray box was dust-free by wiping it down with a wet towel. Everything looked good. Ready for launch. I shook the can and gave the plate some gentle sweeps, but I think I put on a little too much. I came back 30 minutes later and found some of the paint crinkled in a funky way -- like ridges. The temperature was a bit colder this day... maybe 45-50 degrees. A few days later I tried sanding them down, but they weren't going away easily. I gave it another spray and the ridges came back more prominently. I couldn't think of any way to salvage it at this point, so I let it sit for a few weeks.

When the motivation hit, I used a belt sander to remove the paint... down to bare aluminum.

For my second attempt, I did my best to keep the paint area clean. I wiped down the box. I wiped down the plate. The temperature was perfect at 65 degrees. I sprayed with gentle sweeps and made sure not to put too much on. I waited 20 minutes between coats. The can says 10 minute drying time. After the third coat, a weird moire pattern appeared in a few places. I buffed them out with steel wool, cleaned the surface, and gave it another light coat. The moire came back! What am I doing wrong?! This is so frustrating! A few years ago, I painted my Seduction without any of these problems -- same paint, same method. I don't know what's going wrong this time.

I suppose this is a rant more than anything. I'm giving up. I can't stand the fumes or the frustration of not moving forward. I'm going to look for an auto body shop to see if they'll paint it. I can't imagine it costing that much. If you have recommendations for places to have this done, please let me know.

Thanks for listening!

Mark

[ToolGuyFred]

I had problems with my Crack top plate too. This was the first time I had decided to go for a paint finish rather than get the top plate anodised. In my case I tried several different undercoats which claimed to be suitable for aluminum alloys. I finished up with a spray "etch primer". I tested these on a scrap sheet of alloy before I even started with the top plate. The worst of the primers I tried left a coat of paint which could be lifted with a thumbnail.

The finish coat was spray hammer-finish copper. I did my usual (potentially dangerous) trick of three kettles of boiling water in a plastic bucket (in a far corner of the garden) then drop the spray can in to heat for ten minutes. Always seems to give a good finish but you need thick rubber gloves to handle the hot paint tin.

I accept no responsibility for injuries caused by exploding paint cans - I am just saying what works for me (have painted this way for over 20 years and haven't had one pop yet but I suppose there's always a first time...).

[dstrimbu]

... The coat was thin, but looked even. I turned the plate around and gave it another sweep. 15 minutes later, it looked great and was fully covered, but I was determined to give it a thick coat, so I gave it another sweep. ...

Ahhhh, Mark... the agony of anal retentiveness... I know it well, personally.  With the Krylon stuff, anything that resembles a heavy coat will ripple immediately.  If you want to build the finish to a heavy coat, you'll need to apply a dozen thin coats.  It's a chemistry issue, and I've actually seen ripples/moire pattern form when I give a surface just a bit more paint...  that being said, when properly applied, the Krylon paints have excellent durability.  I shot the transformer end bell on my Crack amp with satin black Krylon, and it looks like it was powder coated.

That being said... have you considered using a primer, first?  As Fred mentions, an etching primer like Rust-oleum #249322 will help adhesion.

Your final comment about the body shop - yep, that'll work, and they'll generally do it for a pittance.  My wife and I, in leaner days, had a refrigerator repainted twice at a local body shop - and it stood in three different kitchens over 25 years.

Cheers,

-Don

[Beefy]

When I did the Crack top plate, it was Krylon Hammered Finish straight onto freshly sanded aluminium. The Hammered Finish is a VERY sticky paint, and it came up a treat with four light coats.

But yes, an etch primer first can certainly prepare things for a better finish.

[coca]

Whenever I needed an aluminium top plate painted, I had it done at an automotive paint shop, and had them "VINyL WASH" the metal first, Then finish with an automotive base coat clear coat. I insisted that the top plate should come out like a sheet of glass. For me, that's the only way to go.

Bernie.

[mingles]

Thanks for the suggestions and comments. I thought I could get this right with one or two attempts, but I'm gonna bail out. I don't want to be exposed to any more toxic chemicals. Have you ever read the label on the Krylon can? I should have my head examined!! I've been spraying this in my apartment. I set up good ventilation, but it still takes a day or two for the fumes to completely disappear. I don't have a garage or workspace. It's insane to spray this stuff where you live.

Bernie, thank you for this advice:

> I had it done at an automotive paint shop, and had
> them "VINyL WASH" the metal first, Then finish
> with an automotive base coat clear coat.

I want the top plate to look perfect. The Crack will be on a table next to my listening chair. I've always had a thing for Cary's Jaguar Red top plate:

http://www.upscaleaudio.com/media/catalog/product/cache/1/thumbnail/9df78eab33525d08d6e5fb8d27136e95/s/l/slp98.jpg

I'm planning to build a custom base out of Zebra wood. I think a gloss red top will be a nice compliment.

In any case, thanks for the moral support!

[Doc B.]

This guys says Krylon has a piquant finish and should be enjoyed... well, he can't remember the rest ...
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.losteyeball.com%2Fpics%2F0721051gold1.jpg&hash=f8b5fa19b8985e105f2a4f2d7bf3332f88f5f414)

[Jim R.]

All this red!  I love it.

So far, the only project I have in the works that doesn't have some red on it is my stereomour -- that will be highly spalted birch with walnut trim and recently got the top plate back from the chrome shop with a mirror-like show chrome finish.  The rest of the trimmings on that one will be black and gold exclusively.

Mark, please don't spray that stuff in your apartment anymore -- that's crazy man.

-- Jim

[Yoder]

I like the HammerTone look, but for colored surfaces on metal I use 1 of 2 techniques for my guitar effects pedal boxes.

1) Lightly sand surface (steel wool works great), give it a few coats of your paint (it should not be too cold), then once the paint has set at least 48 hours I hit it with a few coats of lacquer (warning: polyurethane will yellow with time). Krylon makes a good lacquer for metal surfaces that's cheap in price. Let it sit for a couple of weeks (you could try a week, but if you live in a humid area then you may be disappointed with the results,) and then you can start the polishing process.

2) Use the same as above, only I bought a toaster oven and put my pieces in there for 60-120 minutes with the setting on low-med or 200 degrees. Just make sure you never use the oven for food in the future. This technique works well and gives you a baked-on paint surface. You still need to let the paint cure completely before polishing and this can take a few days depending on the humidity.