There was a time when a flat-finished hot rod would've been regarded as either a work in progress or the victim of an oxidated paintjob. Showing up at a show with a non-glossy ride was the car show equivalent of going to church in your underwear. Nowadays, flat paint is almost expected on traditionally inspired rods and customs. For some rodders, a coat of primer is a quick, easy, low-buck way to get a finish on their cars. For a few, a cheap paintjob is a statement against the extravagant paint on over-the-top show cars (and easier than confessing a lack of money or skill). But, many talented builders are covering their high-buck rides with well-done flat finishes, too.

Although some car shows still enforce a "no flat paint" rule, flat has become a legit alternative to glossy. Goodguys sets up special areas for "Suede & Chrome" cars. The Suede Palace is a popular part of the Grand National Roadster Show. The same goes for the Sacramento Autorama's Suede Pavilion.

As flat paint has been embraced by hot rodders, the quality of these paintjobs has improved-or maybe it's the other way around. But, describing a finish as "flat" is as vague as describing a color as "green." When you talk about levels of flatness, you're really talking about the levels of gloss or reflectivity, which can range from a mirror to a cardboard box. If you had a reflectometer in your toolbox, you could measure your paint's reflectivity and rate it on a scale from zero to 100. Paint industry guys love doing this and have specific terms for the various levels:

Less than 10 Flat
10-30 Matte
30-50 Satin
50-75 Semigloss
75-90 Reduced Sheen
More than 90 Full Gloss

What level of flatness/gloss do you want? Is it rattle-can primer or a meticulously prepped and sprayed two-stage semigloss job? Once you've decided on a look, how can you achieve it? In past articles, we asked custom painters for advice. This time, we talked to Brian Lynch-training manager for Valspar and House of Kolor-and a few other paint industry pros for the perspective from the product side.

The most basic, and maybe most common, way to get a flat finish is with colored primer. Shooting primer with no topcoat is easy and cheap, and perfectly appropriate for a low-buck rod, but offers little in the way of protection or durability. Those are secondary priorities anyway for some rodders; for others, a coat of primer is a temporary solution until they're ready for a more extensive paintjob.

Basecoat without a clearcoat is another method for going flat. Polishing would, obviously, defeat the purpose, but sanding with some 1,500- or 2,000-grit sandpaper would contribute to the desired look. Brian pointed out that cool effects can be achieved by color-sanding and polishing some areas while leaving others flat to create a contrast. As with exposed primer, this method has the disadvantage of eliminating the protection of a clearcoat.

At the other end of the spectrum is the full-system job, using primer and colored basecoat and finishing with flattened clear. When shooting a multistage flattened paintjob, Brian prefers to add the flattening agent to the clear instead of to the basecoat, since flattener can affect the paint's color and opacity. Clear does not contain pigments and other solid contents that can be compromised by flatteners.

An intermediate option is to shoot a basecoat, such as a single-stage urethane, that has had the gloss reduced by adding a flattening agent. Flattening agents contain ingredients that, when added to paint or clear, disrupt the clarity of the material, making it easy to get a non-gloss finish in any color you want. In some cases, the flattening ingredient is a wax additive; in other cases, it's an inert physical particulate (silica, for example) that floats on top to prevent reflectivity of an otherwise glossy material.

Wax-based flatteners have the advantage of less cost, ease of mixing, and familiarity. However, the softer finish presents a greater likelihood of "rub back," especially on parts that are handled frequently, such as decklids. Over time, friction can rub out the flat finish, causing it to become glossy. The inert materials in the silica-type flatteners actually contribute to surface hardness, reducing the possibility of rub back.

As you'd expect, adding more flattener reduces the level of gloss-but higher-quality paints, with more solid content, generally require more flattener to achieve the same level of flatness. According to the Gloss Reduction Table in the Valspar Technical Data Manual, a two-to-one mix of Valspar SunCryl (a lesser-priced single-stage enamel) and FX-01 flattener reduces reflectivity to 11.6, between flat and matte. However, a two-to-one mix of Valspar Omega 2K single-stage polyurethane and FX-01 only drops reflectivity to 92, which is still a full-gloss finish. Clearcoats tend to drop more quickly than high-quality urethane basecoats-which is another argument for adding flattener to the clear instead of to the basecoat.

There is no single definition of a flat finish, but the right combination of colors or levels of gloss can make a stronger impression than shiny paint. It may not be enough to get you through the gate at a "finished-car only" show, but it may be enough to silence those people who can't look at a low-gloss car without asking, "When are you gonna paint it?"