Customers desire it as it shows all the fabrication in an unadulterated perspective, naked and visible for all to see...the colored HAZ from welding, the disparate hues of the brazing material and the base metal, and the industrial beauty that is the fabrication process.
Though desired and popular, the concept of a "raw" finish on frames is seldom embraced by builders for a variety of reasons, but the most typical is the short term durability of the finish. Unlike Titanium and Aluminum, where oxidation forms on the surface and creates a protective layer over the substructure, oxidation of the steel bike is not at all desirable, manifesting in slow corrosion of the material in the form of the "R" word (shhh...it's RUST).
To protect the steel frame, the liquid paint process uses three different layers; the primer layer which is chemically designed to stabilize and seal the material, the color layer for all the purtyness you desire, and the clear layers to protect the colors and provide depth of vision. Liquid finishes are designed to chip or fail under stress/impact, releasing from the primer layer leaving the protective sheath in place. Without the primer layer, oxidation will ensue.
Powdercoats, which are becoming more popular with builders, protect the steel frame in a different fashion. Using an plasticized dust that electrostatically binds to the frame and then melts around it much like saran wrap, it is a very different process than liquid paint. Powdered finishes may use a single to multiple layers. When a powdered primer is used as the first layer, it will protect and seal much like the liquid primer, keeping oxidation physically and chemically at bay. Color and clear layers can then be built upon it. However, if pigmented layers are used without the primer, it merely acts as that proverbial saran wrap, allowing moisture to creep between the base material and the powder coat.
To achieve a raw finish, a liquid or powder clear is applied to a carefully prepared frame without a primer layer. This transleucent coat allows for the underlying characteristics to shine through. However, what you are sacrificing is the durability of the finish. In time, oxidation will creep between the finish coat and the base material, showing through in ugly spider rust and discoloration.
Early last year, I painted up one of my sponsored riders bikes in a hybrid finish; powdered clear with liquid colored panels on top. My goal was two fold...to allow folks to see the level of craftsmanship that goes into a handbuilt frame and to have a visual object lesson at the end of the season to share with y'all on the durability of such finishes. This bike was raced in all weather conditions, long off road 100's, short dirt criteriums and everything in between. The consistent factor was that it was generally abused, neglected, and put away wet in our humid Ohio climate. Anywhere that moisture can get in, it will. Most often the entry points are around the headtube after facing off the paint, areas with high wear due to cable rub or other friction, and places where the finish has been breached due to stone impacts or other damage. The pics above showed the frame right after it was completed, now here are the pics one year later.
Caution, not for the faint of heart :)
From a distance, she still looks good, maybe not as shiny and new as early in the year but still hanging in there.
Pretty yucky, eh?
Please remember, this activity is going on under your powder coat finish if your builder is not using a special primer...I restore a lot of frames and this type of corrosion is common place. Just cause you can't see it does not mean it's not there.
So, as much as I like to check out the raw finish too, if not properly prepped and cared for, the beauty can quickly turn beastly.
Jeffs frame got stripped and blasted, and is ready for it's new liquid colors for the 2010 season. Though I'm sure it will be just as beat on by the end of next year, I can assure you that the frame will be preserved and protected from this type of damage when next ready for more love.