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plug finish?

Old 12-06-2009, 10:21 AM
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Default plug finish?

I am trying to find out the best finish for a plug. Should I paint it clear it and buff it or can I spray a PPG white epoxy primer and sand and buff from here. Thanks.
Old 12-06-2009, 12:03 PM
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Default RE: plug finish?

Lots of guys finish it in black so everything shows. You'll want to treat it like a finished plane, prime, sand, paint, sand, sand .sand, buff, buff. It can't be finish too well, any imperfections will be in everything you make.
Old 12-07-2009, 06:41 PM
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Default RE: plug finish?

I've used gray for my plugs, some people like black or white.

You'll want to use a quality urethane primer before painting, then a couple good coats of paint. After that, you can buff, going from hard polish to super-soft "shine-maker" polishing compound. Make sure to use clean rags to buff.

An alternative is to spray urethane clear lacquer or clear coat on top of the paint to further protect it. I've also found that clear coats develop a much better shine if polished well.

Oh, and remember - an extra half an hour of quality put into the plug will mean an entire hour less of work needed on the final product.
Old 12-07-2009, 07:18 PM
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Default RE: plug finish?

In addition to all of the previous advice. A super gloss finish in the mold is not just for cosmetic reasons. Glass parts will release easier from a mold with a gloss surface. In fact, unless parts are to be painted in the mold a gloss finish on them is not desirable as the surface has to be cleaned and sanded prior to painting.

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Old 12-08-2009, 03:17 PM
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Default RE: plug finish?

Re plug color, Generally darker colors will better hilite reflection from indirect light & contrast more so you will be able to see any underlying waviness (the polished potatoe syndrome) as well as gloss. Dont make it black if you are for example using black tooling gel on the female mold. A different underlying plug color can help show if tooling gel might be thin like on sharper corners or the apex of a plug. Generally dark female molds are better for hand layups, but if you are pre-painting or vac bagging, its not that big a deal.

Im not a paint expert but I think clears are formulated for buffing & polishing whereas pigmented paints (containing solids) maybe not as much. Just look at any show car, its always the clear you are looking at. I think clears are also less permeable so should act as a better seal for release agents. Having said that, Ive always used 2k catalysed car paints & they buff out real nice. Of course, wax mold release enhances this some more but take the paint finish as far as you possibly can, it helps with every step thereafter.

Old 12-09-2009, 12:56 AM
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Default RE: plug finish?

I use PPG Deltron urethane high build primer. Primer alone works great. Dark grey and wet sands/buffs out to a mirror finish. Unless your plug is perfect, I'd be afraid that a low build epoxy primer would be difficult to buff out without multiple applications. I do however use white epoxy primer to product primed in the mold parts. I'd agree that dark colors seem to make it easier to detect flaws. For that reason, I also add black pigment to the tool coat of the mold. Dark color also makes it easier to see if the layup is sitting correctly.

Pics of a plug I did a few years ago can be found here.

Working on a plug now for a turbine, plan on using the same technique as it worked well for me previously.

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