Clearcoat Question
 

A couple weeks ago I stripped down my beater frame, primed it, and painted it with Duplicolor Automobile rattle can paint. It looks like a total sex machine now, but the paint is chipping pretty easily, and it seems destined to return to beaterland in the not-too-distant future.

I neglected to clear coat it, because the guys who sold me the paint told me that automobile paint shouldn't be clearcoated. I recently decided they was wrong and that I would put on a clear coat after touching up the scratches, but I've since gotten the same anti-clearcoat advice from two other paint shop guys. Do these guys know what they're talking about?

Since they probably don't...any suggestions as to how to clear coat it without taking off all the components? (not exactly a quick process, and I'd rather not repeat it)

Paints generally are presented in complete systems. For example, Duplicolor's Engine Enamel system has a color component and a clear component. Some systems require a clear component, some don't have one, and in some a clear is optional.

Read the back of your paint can; if it says something about needing a clearcoat over it, then you'll know that your particular system does require a clear. Otherwise, if you want, you can go back to the store where you bought your paint and see if they have a "gloss clear" that you could use. Be aware, however, that the "gloss clear" may be identical to the paint you've already applied to your bike except that it won't have any pigment, and hence probably wouldn't give any greater resistance to chipping. Make sure to stay within the same system, because a different type of paint could potentially cause problems such as lifting or wrinkling the color coat.

Unfortunately, rattle-can paint is not as durable as professional-quality paints. You can search the forums for more information on painting your bike; it's a very common topic and you're likely to find more information than you'll ever need.

BryE is sort of right.

Let me tell you first that FULL curing takes at least 3 months some people go as far as waiting 6 for reaching total hardness before assembling all together.

Yes you can absolutely apply clear coat to acrylic Duplicolor, for maximum durability I’d recommend the Duplicolor’s clear coat for aluminum (car) rims. It is especially formulated to be durable & withstand harsh chemicals BUT here’s the catch: it must be applied within 1-2 hrs from the last paint coat otherwise it just cures to a beautiful texture & I don’t believe you want that.

So go ahead get yourself at least 3 cans of CC & 1 of paint. Give it one thin paint coat all over serving as a touch up & “fresh” base for CC. If you are going to apply decals do it now.
Apply at least 3 thin layers of CC & let it dry. It is normal to see some cloudiness especially in humid environment don’t freak out. It dries clear.

Agree with spinner guy...let the paint cure (after you apply the clear coat) until it is hard and well bonded.

ANY paint that comes in a can is an enamel, which means it uses the evaporation of the base solvents to facilitate in the curing process. Real automotive Urathane uses a two part mixing process. A resin, and a hardener which catalyzes a chemical process that causes it to harden, along with the evaporation of solvents to facilitate curing.
Two part automotive urathane is the best way to achieve a proper finish that is hard enough for general use on a bicycle. Enamels will almost always chip and flake with wear and tear.

If you don't have painting equipment, ie a spray gun and air compressor, then the local paint shop can pre-mix clear coat into a spray can for you to use within 24 hours of mixing. After that, it will harden in the can, and be useless.

I used Duplicolor with a clear coat
 

About six months ago I repainted a fork with Duplicolor and the the matching Duplicolor clear coat (done the same day). About a week later I was shocked at how delicate the paint was. Fortunately I have five bikes and I just used another for the last six months. Recently I took the painted bike off the rack, and I was once again shocked at how strong and durable the paint had turned. The paint has now been polished, waxed and the bike gleams, looking quite proffesional. My advise is to paint it and wait out your time.

Garth

What they said ;-). Also, heat will help it cure faster. I painted a (car) part that went in the engine bay with regular ol' spraypaint (rustoleum I think). It got rock hard nice and quick (a week? maybe two?). Of course you probably can't bake your (fully assembled) bike in an oven, but leaving it out in the sun will probably help it cure faster.

Is Duplicolor the most durable and economical out there these days? I was thinking of painting an old steel bike with columbus steel tubing - lots of abuse while sitting in storage and would like to get it back on the road.

Duplicolor and Plasticote are the most readily available decent quality spray can paints. Durability will jump exponentially when you make the step up to a urethane clearcoat(which is sometimes available in spray can) which will be best sprayed with a gun. The purpose being, the gun-sprayed clear will require the hardening agent to be mixed into the clear and will have a limited work time in the gun before it hardens. This is why it will harden faster and more thoroughly than the can-type which has no hardener.
The Martin-Senour paint system is what we used at the car restoration shop, which is available through NAPA Auto for a very respectable rate. DO HEED THE SAFETY NOTES however. Professional paints are fun to work with and make lovely results, but they do need to be treated with respect.
Generally, clearcoat should be the identical system as the color(though there are crossovers, listed by the paint mfg or shop) and applied within the "tack range" of the color. This is so that the evaporating hardener and solvent fuse through the clearcoat(not to be confused with blending of the color), producing for all real reasons a solid chemically continuous layer. This applies to both enamels and urethanes.
All paints on metal will benefit from a heated dry time. Factory paint shops, both automotive and bike are heated to 70f to paint, and turned up (around 150f) to cure immediately after application. When it is immediatly following application(particularly with urethane(which has a slower dry time at first) it will make the surface "flow" into a glassy smooth shine. Well worth it if you can figure something, not to mention its safer to handle without scratches when assembling.

Hope this doesn’t qualify as a hijack attempt, but I have a related question.

What if I wanted to apply some painted details. . .say, paint the lugs a different color or some home-grown graphics? In other words, small batches of paint.

If I went the Duplicolor route, with Duplicolor Clearcoat, am I restricted to using Duplicolor for the small-match details paint? Could I use something like Testor model paint?

Thanks!!

Do a test patch under your bottom bracket and find out.

(I find so much advice about what paints will work on what, and a lot of it doesn't seem to actually apply - while other bits do. I'd say just give a little test and see. Proof in your pudding.)