Wow! This could be a real concern...
The easiest way to attempt frame touchup is to find the ***exact*** manufacturer and model of paint used in the original paint job. Certain vintage frame builders chose specific brands of paint to complete their frames. Otherwise, you are entering a real minefield of choices regarding different colors, shades, and types of paints that are available.
Prehaps the best starting point is to obtain a paint manufacturer color chart and try to cross reference the frame paint with the chart. This is best done in bright sunlight or a starndard bulb where subtleties of the frame paint become more apparent. Floresencent lights are not good for paint matching because it is harder to accurately compare colors. The minefield you have to navigate is that the color and shade of paint changes over time and even between batches of paint mixtures. Colors that fade due to sun, heat, untraviolet exposure, etc. can affect paint so that exact color matches can be very difficult. I read recently that Dupont, a major paint manufacturer, now produces over 300,000 colors variations that can be made through any of their paint distibutors!
For touchup, the rule of thumb is that enamel paint can be applied over lacquer or urethane, so enamel is probably the best choice. Use a wax remover like denaturered alcohol on the area to be touched up. To enhance adherance, gently wet sand with 1000# grit sandpaper in circular motions to "scuff up" the paint. Mask off the area that needs the repaint. Some manufacturers have colors available in touchup bottles like nail polish, small spray cans (like Duplicolor), and others require a mix of different components to arrive at a custom mix.
When applying paint by brush or spraying, the hardest color to touchup is white because I small change in shade stands out like a sore thumb. Some say that black color is the easiest to touchup which is good for bike frames, but on a car with a large surface area, black also shows touchup areas easily unless blended in. Enamel solid colors are somewhat easier to try to match. Metallic colors are among the hardest to touchup because of variations in the paint due to metal flakes in the paint, types of paint, etc. This is why it is important to find the original paint manufacturer if possible!
I hope this helps...
Regards, Steve Neago
> Hi all,
>
> I was looking for some pointers on touching up scratches and/or chips in
> paint. I have one good size 4mm chip and was wondering what the best way
to
> touch it up is since I am having less than spectacular results.
>
> Should I just drop a glob into the chip and then sand it down to make it
> smooth after it hardens or should I try several thin coats to fill it in
> since it seems deep.. Also, what works best? Fingernail polish? Testors?
Auto
> Paint? Should I clear coat? I know the goal is to protect the metal but
would
> like to make it look as good as possible.
>
> Scratches would pose a different problem and I guess would require we do
not
> drink that espresso beforehand.?. A steady hand and a decent brush.?
>
> Mike "Stamford bound, no rides for two weeks" Wilkinson
> Parker, CO
>
> ps. Signs you are a bikeaholic: You buy a bike just so you can ride when
you
> are on a buisness trip! Eyeballing an ebay sale close to where I'll be for
> some cheap thrills and a chance to spin the legs:)