Rickresource Rickenbacker Forum

I have just finished machining* my new 4001 pick guard out of 3mm clear acrylic, and am ready to apply the gold finish to the back. I was wondering how important it is to choose the right finishing product.

Will automotive touch-up spray do the job, or do I need to specifically hunt down some gold (acrylic, water based?) lacquer to do the job properly?

Will any gold colour look pretty much the same, or is it important to get exactly the right hue?

Do I need to evenly dull the spraying surface on the acrylic sheet, or just peel off the paper and spray right away?

What does the final clearcoat achieve, if it's exactly the same product as the the gold coats?

*Note: My machine is actually a hand file, and it took bloody ages!

The biggest problem facing you, Mark, is not the "bloody ages" but the bloody edges!

Acrylic sheet is not stress-relieved, and will crack seriously along those filed edges if the sheet is not annealed post-machining. If you want to demonstrate this to yourself, take one of your scraps that you cut off the sheet when you were making the pickguards. Try to get a piece about 2" or 3" square...

Pour some denatured alcohol or rubbing alcohol into a glass or a clean tin can (sardine can?). Toss the scrap of acrylic into the alcohol and pull it out after a minute or so.

What do the edges look like now?

This is what the solvents in any automotive paint will do to the edges of the acrylic pickguards. Solution: sand the edges lightly with #600 wet or dry, until they are nice and smooth. When you paint the backs of the guards, get a minimum of paint on the edges of the acrylic. This means holding the spray can or gun straight-on, not at an angle.

Automotive touch-up spray can be lacquer, enamel, or a blend of the two. Water-based lacquer will not stand up if you can even get it to stick to the shiny acrylic. If you sand the surface of the acrylic sheet, you will stress-relieve it and there is a possibility of cracking then, too.

No clearcoat is necessary, as you are painting the back of the acrylic.

Not all golds are the same, as your eyes should tell you. You will need a light brassy gold, if that's any help. Do not buy gold "plating" paint, buy a gold car color.

Find a color you're happy with, in an automotive touch-up lacquer. Immerse the can in 120 F water (no hotter--explosion risk) for a few minutes before spraying--this raises the pressure inside the can and gives you a finer spray. Use four or five very light coats. Wait overnight for it to dry.

Is it possible to anneal the machined acrylic, (in hot water or an oven) or is this impractical?

Paul. Am I reading your post correctly, are you giving advice on how to get the best results from a can of s ss ss spray paint?

You gotta learn to walk before you can fly like an eagle, Brian...

Now I feel better. I know how much you dislike aerosol products and I was having trouble reconciling what I had read. LOL

Somewhere, sometime, somebody posted that one auto spray paint which matched Ric gold pretty well was Duplicolor "Gold Dust Metallic" # EDSCC343. I haven't gone out and bought any yet, but wrote it down and stuck it in my wallet - just in case of an emergency....

This is a good place to start. If you have a gold TRC that you're trying to match, however, best to spray out a sample first. Not only has RIC used a few different golds over the years, but variations in application technique when you spray a metallic onto acrylic can give you a color that can vary by two shades or more.

Hey Paul, If you get time, can you expound a bit on the stress-relief concept? I'm a little foggy on what you're getting at and just what forces are at work.

As best as I know how, and it's personal experience backed by practical knowledge, but a chemist could really give you more of the nuts and bolts of how...

When sheet acrylic is manufactured, the process leaves unresolved stresses in the molecular matrix. The plexi has flaws, just like a diamond.

Any sort of aromatic solvent attacks the plexi whenever a flaw is exposed. Since the flat sides of the plexi are annealed in manufacturing, the stress flaws are accessible best through the edge, especially when the edge is subjected to some sort of trauma--sanding, grinding, and even some types of polishing that do not heat the edges.

Apply a solvent like alcohol to the edge of a just-cut or just-ground plexi sheet, and you will immediately see little cracks begin to form, which eventually could take hold and cause the piece to fall apart, like a tempered glass windshield when it is struck with a sharp object. One difference--the crystalline structure of acrylic is more regular that a tempered glass winmdshield, judging by the shapes of the pieces after they break down.

Thanks, Paul. I hunted around for home-builder annealing techniques and found this, which was pretty typical of most instructions, but seemed do-able at home.

"Annealing

If sheet stresses caused by cutting are extremely high,crazing (fine, visible cracks that appear in the sheet over time) will occur at joints, bends, cuts, drilled holes and other fabrication areas. To eliminate the possibility of crazing, the fabricated sheet should be annealed. Annealing is a simple heating procedure which relieves stresses without changing the shape of the fabricated sheet and often increases sheet strength. To anneal sheet after fabrication: 1. Preheat oven to 175°F (80°C). 2. Remove all masking from sheet. 3. Place fabricated sheet in oven and heat it 1 hour for each millimeter of sheet thickness.(Example: Heat 3 mm sheet for 3 hours.)Minimum heating time = 2 hours for sheet 2 mm and less. 4. Turn off oven and let sheet cool slowly."

Here is another one that's a bit more technical.
http://www.polyfab.biz/annealing-acrylic.htm

I did try water-based hobby enamel (made for model airplanes, etc.) with my airbrush on a scrap of plexi and it went on evenly. Adhesion isn't spectacular (passes the medium fingernail pressure test, but not hard pressure) but it would probably work for an installation like a pickguard where it's protected from abrasion. You pretty much have to own an airbrush though to be able to apply it.

Water-based paints do not require that the acrylic be annealed.

The only caveat when annealing in a home oven is that you have a good thermometer, as most home oven thermostats are not too accurate.

Cresent Bronze Powder Corp. 1-800-445-6810
Mix bronzing powder with clear lacquer or C.V. and you will have exact Rick Gold. About $40.00 a quart can.

Thanks, Dale.

I avoided stating this because Mark does not have a spray gun.

Also, I understand that Rickenbacker no longer uses this formula, but since when, I'm not sure. But I'm pretty sure that although the pigment source has changed, the color remains pretty much the same.

You are very welcome Paul, and by the way, Very Nice Refins you are posting.