October 03, 2008

#48 - Window Frame Polishing

After a lot of trial and error, I've come up with an efficient process for removing the heavy oxidation and corrosion from the window frames and creating a near-mirror finish. My method isn't cheap. It requires an investment in consumable abrasives, pads and polishing compounds. I haven't added it up, but I know I've spent more than $200 in consumables just to polish the 9 windows' frames. That's in addition to an air compressor and an angle grinder. After trying it a few different ways, I'm convinced the best tool for the job is a pneumatic 1/4" right angle die grinder. Get a cheap one for under $30 on eBay.

Here are the steps on the aluminum frames:
1. You can waste a lot of time trying to get the heavy oxidation off your windows with the wrong tools, abrasives and polishes. You have to overcome your fear and be aggressive. This isn't the trailer's ALCLAD skin so you can use tools you'd never dream of using on the rest of the trailer.

Use 80 grit (yellow) 3M Bristle Discs in the 2" size on your grinder. Grind all surfaces that will be visible after installation. Bristle Discs are going to scratch the hell out of your frames. But they're fast and they get all the oxidation and corrosion off that you're going to get off. You might want to buy a few 1" bristle discs, too, for tight spots. Do NOT use the 3M radial bristle discs. They gouge.

2. After you've scratched all the severe oxidation and corrosion off, you need to fix the scratches. Get some 320 grit and 400 grit wet sandpapers and hand sand everything you just took the grinder to. You have to go over it a lot to get out all the swirls from the bristle discs. Don't hurry this step. Clean frequently. Make sure the swirls are gone. Now instead of swirls, you will be left with finer scratches going the length of the frames. The second photo below shows the "before and after" of the hand sanding.

3. From here on, you'll be back to the power tools. Place a cotton 1.5" cylindrical or goblet-shaped buff in your grinder. Use Nuvite F9 polish and slowly polish everything that has been sanded.

4. Use a different buff to do it again with Nuvite C polish.

5. At this point it looks pretty good. If you would like, do it again with Nuvite S and a third buff, but I'd recommend waiting until it is installed back in the trailer before worrying about Grade S.

A note about what to polish and what not to polish... While you want to get all the oxidation and corrosion off all the parts, some parts of the frame don't need to be polished through all 5 steps above. Obviously the exterior of the front frame should be a mirror. But the backs of the back frames will basically not show at all and can be left in a clean but unpolished state.

October 01, 2008

#47 - Proper Window Restoration

To begin a window restoration, the window needs to be disassembled. Front frame and back frame are separated at the hinge. Then the vertical center channels are removed from the frames. Take care with the extruded aluminum front frame channels. The 4 rusty mild steel screws that hold them in place easily break off inside the channels.

After the channels are off, the old screen is removed from the back frame and the glass is removed from the front frame. To get the glass out, you'll be removing lots of little rusty fasteners that secure the L-shaped aluminum glass holders behind the glass. Throw the screws and nuts away. You can get new screws and tension nuts from Vintage Trailer Supply.

All the dismantling is necessary so you can de-rust and repaint the steel back frame channels. You're also going to replace the old screen material, get new glass, and then spend hours and hours removing corrosion and polishing the aluminum frames. The photo below shows a pile of back frames. The first two frames show what they look like when the oxidation and corrosion have been mostly removed (but before detailing). The rest show the extremely heavy oxidation and significant corrosion you'll encounter.

If you've polished an Airstream, you know about oxidation. It's not quick to remove, but on a trailer skin it isn't really that big a deal because the oxidation is generally even and rather thin. You can read my article on polishing an Airstream if you don't know the basics.

Polishing 53-year old window frames is nothing like polishing an Airstream. Repeat: nothing. Rub your finger across the back frame's sill. Feel how rough that is?. That's extreme oxidation and corrosion. The oxidation builds up into little craggy mountains of oxide. It cannot be polished off with aluminum polish. Don't even try. You're going to be grinding it or sanding it off. After you get it off, you're going to see little pits and valleys in the aluminum. That's corrosion and you can't entirely fix it. You can minimize it by continuing to grind and sand, but some of it is going to be there when you're finished. Fortunately, the only place the corrosion will be especially noticeable after you reassemble everything is in that exterior sill area. And that's not visible when the windows are closed.

In my next post I'll detail how to remove the severe oxidation.