Black Trim Restoration
by Paul Gasparola and Angela Brown
Professional Detailers Association
It is commonly believed that black is universal or always the same. It is not. Until recent years, that was true of gloss black used on automobile exteriors. Even here, recent developments have produced variations such as metallic blacks
Of prime importance to restorers are the black finishes used on many of an auto's components. As a car show judge, I often see gloss black, ever as shiny as that used on the exterior, applied to firewalls, wheel wells and other under hood components. In most cases, this is wrong.
The variations in black are typified by paint supplier listings. For example, the Eastwood Company offers chassis black, radiator black, under hood black, and satin black. Similarly, an examination of paints in hardware and automotive supply stores offer more black paint names. What's a restorer to do?
This column will provide some technical and historical background about the variations in black paint coupled with some experience-proven tips to guide you in applying the correct black finish to the various parts of your restoration project.
The variations in black colors in automotive components are differentiated by the degree of gloss. Paint gloss is measured, using specialized instruments called gloss meters, in degrees of the angle of light reflected from the source. Hence, degrees are the measure of reflectivity and range from zero degrees (a flat) to 100 degrees (full gloss). In paint practice, some prefer to specify the degree of gloss as percentage of full gloss. Therefore, 100 percent gloss is the same as 100 degrees gloss-both mean full gloss. Similarly, a 60 percent gloss is the same as 60 degrees gloss.
Any type of paint-enamel, lacquer, their acrylic modifications, and urethanes-and any color, not just black ran be mixed to any degree of gloss by adding an amount of the correct flatting agent to the base paint. To achieve a specified end result, a paint mixture is prepared, a test panel coated, and the resultant finish measured with a gloss meter. It is a trial and error process to obtain the correct volume of flatting agent to be added to the volume of base paint. Paint manufacturers provide these findings in the mixing formulas that they supply to their distributors. Alternatively, a manufacturer, with the desired degree of gloss who, in turn, determines the appropriate volume of flattening agent for the paint mixture. Using degrees of gloss instead of percentages avoids a common misinterpretation that the percentage is a measure of the amount of flattening agent added to the base paint.
Without a gloss meter, which costs between $2,000 and $3,000, exact measurement of degrees of gloss is not possible. Even those who use specifications and instruments to obtain a desired result allow for variation. This variation exists because application methods-spraying or dipping-application conditions, such as air volume, gun-to-object distance, humidity, and solvent: paint ratios, all affect the final result.
There are four gloss terms that enjoy standard usage in the coatings industry:
But these terms do not prescribe a single numeric degree of gloss, but rather a range. The accepted ranges in degrees of gloss for each term follow:
Distinguishing between these ranges can be done by eye, a gloss meter is not required. Conversely without a gloss meter, it is not possible to determine if a semi-gloss black is 50 or 60 degrees gloss.
There is another term that is commonly encountered in coatings literature-satin. This term is a marketer's term and is not employed in technical discourse; theoretically, satin could apply to any degree of gloss other than 100. However, over time, it has come to be commonly associated with paint with a gloss in the eggshell range.
The black paint applied to frames suspensions, under hood components and the like was intended primarily for protection. Economy was the driving force. Chassis Black came to be a generic term for a fast drying enamel, sometimes containing coal tar, specifically intended for use on frames and suspension parts. As a cheap coating, there was little concern about the degree of gloss although it is typically mixed without a flattening additive. It did not age well and soon lost its gloss. Additionally, the condition (degree of smoothness) of the substrate to which the paint is applied also affects the paint's reflectivity.
Using paint with less than 100 degrees gloss had another benefit; it obscured manufacturing marks. Marks remaining from drawing, stamping, and forging remained; usually there was no attempt to remove them. Accordingly, many variations in gloss are found on automotive components.
During the muscle car era, a special black paint called performance black was widely used for hood stripes and similar applications. It was typically lacquer-based, flat in gloss, and employed additives to resist glossing.
An automobiles components were produced by many different suppliers. Even if the same supplier was used, that supplier might have had more than one manufacturing plant. As previously mentioned, the method of application also affected the degree of gloss. Components were delivered and placed into bins along the assembly line and mixed with those from different lots and, potentially, different suppliers. Even within a particular car fine tend car model in a given year, there were differences between assembly plants. Therefore, conditions are ripe for variations to exist.
In absolute terms, there is no one specific degree of gloss that is correct. However, generally, the ranges of gloss described above held true, i.e., components intended to be semi-gloss will be in that range in most cases. But, like a lot of other aspects of car manufacture, fasteners for instance, production was most important and a batch of components would not have been rejected from use just because the degree of coating was not "right."
Determining what is right is the first step. Your car is often the best source of information. If you intend to show the car for judging by a particular club, then you should follow the guidelines that club supplies. If you can locate degree of gloss information for a component on a car line in the same time period, it can be reasonably assumed that the same component in another line by the same manufacturer, e.g., GM, would be finished the same way, unless the component was unique to a particular car line or model.
With the right degree of gloss determined and the parts prepared- cleaned, primed, etc.-you are ready to paint. You can mix your own paints in the trial and error method that manufacturers use to determine their specifications using gloss black and flattening agents from your paint supplier. I find, however that a little careful shopping can eliminate this step and provide a source of ready mixed paints in bulk and spray cans that are, either enamel, lacquer, or epoxy-based. Remember, your car will be judged visually, so if you stick with the four ranges-flat, eggshell, semi gloss, and gloss-the end result will replicate "as manufactured conditions".
If you have a large number of pieces to paint at the same time or ones that are large in size, such as wheel well liners, hoods, etc., then a spray gun can provide the best finish. However, for small lots and small pieces, I favor spray cans. They offer convenience, speed, and minimal overspray and minimize waste and cleanup time.
Remember to replicate "as manufactured" conditions, apply just enough paint to provide full coverage with no "holidays."
© 2000 Paul Gasparola and Angela Brown (Member Profession Concourse Detailers Association)