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      04-10-2009, 02:13 PM   #2
nadaclue
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part two

DIY Roundel Guide
Part 2

First off, my apologies for slacking and never getting around to finishing this write-up much sooner as I had promised. I got sidetracked by another project, refinishing a set of Breyton Inspirations that were color matched to my car and the roundels got pushed to the side. Plus I have a really bad habit of starting a project and then finishing it a year later.

Step 6: Painting the plastic back half

Now that everything is apart and sanded, it’s time to start laying down some paint. Here are the coatings that I used, all can be purchased from your local parts store as I didn’t use any sort of specialty paints. For the plastic backing half of the roundel, we need to use a plastic adhesion promoter and your color of basecoat. This basecoat will form the visible edge of the roundel:



And my black basecoat:



Step 6.1

Since we’re only really concerned with the outer edge of the roundel and should have gotten sanded when you sanded the aluminum face, there’s no reason to worry about further sanding. Just follow the directions on the spray paints and remember to try and do this in a clean, well ventilated environment. These are solvent based coatings and are flammable as well as contain chemicals that can be harmful if inhaled.

I applied 2 light coats of the adhesion promoter to the plastic, making sure to avoid runs and doing light coats.





Follow the directions for recoat times here, you’ve done all the hard work and you don’t want to have a shoddy looking piece because you rushed it or let it sit to long. With the adhesion promoter there is a very specifice window of time when you need to apply your basecoat, make sure to read and then re-read the directions carefully.

Step 6.2

Once I had allowed the minimum amount of time to pass, I put on a light coat of the black basecoat. Again, work in multiple light coats of paint. Don’t worry if you don’t have that high gloss shine the first time around, it’ll develop over multiple coats.

First coat:



And after my third and final coat. You can see much more shine/gloss has developed:



And that’s it for the backing. Again, remember that you can use any color you want here and it’s dependant upon your desired design. I wanted a black trim ring around mine to help set off the colors without being overly bright.

Step 7: Prepping and painting the aluminum front half

Now that the back and ring are painted the color you want, it’s time to move your attention to the front half of the roundel. Again, remember to follow all safety precautions and directions on your paint. The time you’ve put in so far to this project would be wasted if the finished product starts falling apart, and no project is worth damaging your health.

All paint was again sourced from my local auto parts store, nothing fancy or high end here but it gets the job done. For the roundel front we’ll need an etching primer, sanding primer and most likely a white basecoat. More on why you want a white basecoat in a bit.

The etching primer insures a good bond between your paint and the aluminum substrate. Aluminum is difficult to stick to, but the nature of etching primers ensures a good bond and substrate for your sanding primer and basecoat.



The sanding primer is going to allow you to build up the surface of the roundel and help hide that ghost image that we have left. Essentially what it is is a paint with a high solids content that dries very fast. This allows you to build up the primer and sand it down flat and smooth, hiding the raised ghost image.



And finally the basecoat. As I said, you’ll most likely be using a white or other light colored basecoat. I’ll explain why when we get to actually putting the design onto the roundel.



Step 7.1

Begin the painting by ensuring that the aluminum roundel is clean and free of any finger oils or sanding contaminents. Get out that acetone that you used earlier and thoroughly wipe everything down. I highly suggest where rubber gloves at this point. The oils from your hands can make it extremely difficult for the paint to adhere and you may end up with adhesion failures down the road.

As I said, the etching primer is designed to create a substrate that your primer / basecoat can stick to. This coating goes on very thin and is merely there to act as corrosion resistant barrier as well as bite into the aluminum. Two very light mist goes works well, just ensure that you end up with a smooth uniform finish and follow directions for re-coating on the label of the can.

Here you can see what my etch primed roundel looked like. You can see some of the ghost image coming through, but don’t worry as we’ll take care of that next.



Step 7.2

Once your etch primer is properly cured, it’s time to put on the sanding primer. This is a multi step process that helps smooth everything out. First I put down two coats of the sanding primer and made sure I had a nice smooth uniform film.



Then once it was cured per the cans instructions, I sanded it with 400 grit sandpaper. Don’t worry about sanding down to the green etch primer. Just be sure NOT to sand through the etch primer to the metal other wise it’s time to start over.

Repeat the painting / sanding step until you are happy with your results. How much time you initially spent sanding the aluminum down will dictate how many coats of sanding primer you’ll need. The smoother the substrate was to start with, the less primer you’ll need. I ended up with just 2 coats of primer until I was satisfied. Don’t be worried if you see some etch primer still coming through the black. The way we’re going to put on the design will help hide the minimally ghosting that’s still left. As long as it feels relatively smooth to the touch, you’ll be good to go. Here’s my finished results:



Step 7.3

Now for the last bit of painting, the basecoat. Wipe down your sanded roundel with acetone once the primer has fully cured in order to remove any dust that may have remained. Don’t worry if your rag gets a little bit of black transfer, just don’t saturate the part so that the primer begins to soften. If this happens, put the roundel aside for a day and let the coating regain its hardness.

The basecoat is pretty simple and straight forward. Again, be sure to use multiple light coats of paint. We want full color development and we don’t want a grayed out coating. Once you have a smooth finish, let it cure out for a couple of days before continuing. We want to make sure all of the solvents are out of the paint before we begin applying our image. Also, it’s important to have a smooth appearance here with no grit / dirt in your paint otherwise that will show through image. Feel free to wet sand with 1800-2000 grit sandpaper to get it smooth as possible, since I work in a clean environment that wasn’t necessary for me.





And here’s the front of the painted roundel sitting in the black back piece. The black rim will nicely frame out my design later:



So far so good. Now the painting part is done on the roundel and its time to get onto the fun part of the project, picking out your design and seeing the fruits of your labor come together.

Last edited by nadaclue; 02-13-2010 at 03:29 PM.. Reason: finally put up part 2 !
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