Q: Sometimes, after I’ve sanded and finished a piece, I’ll take it outside or into another room and notice scratches and machine marks on the surface that I didn’t see as I was working in my shop. What can I do to make sure my work isn’t covered in scratches waiting to surprise me in a different light?
-Grady Housel
Charleston, SC
A: As we excitedly approach the “finish” line of our projects, we need to slow down and check for scratches and tool marks. But even taking our time won’t do the job unless we inspect our work under light cast at a low, “raking” angle. Raking light is a critical tool in the surface preparation process. It spreads across the work, emphasizing dents and scraper/sandpaper marks, accentuating shadows, and pointing to missed spots that are difficult to see with standard room lighting. It doesn’t really “highlight” trouble spots but instead “lowdarks” them with shadows. I know I just made up a word, but it works. If you are lucky enough to have windows in your workshop, you can borrow raking light in the morning as the sun rises or in the evening as it sets. If not, you can use adjustable architect lamps, which mount to the workbench in 1⁄2" holes as shown. I use three such lamps on each bench in my shop. This set-up allows me to move the lamps around without having to fuss with unwieldy clamps or jigs, as I periodically inspect my pre-varnish surfaces. As I check over my work, I pull my lamp down to just above or next to each surface, casting light across the plane, creating shadows where there might be scratches.
Before you start applying finish to a piece, look over your work under raking light again. Be sure to pay close attention to the edges of surfaces, where most defects hide. If you find scratches or machine marks, don’t try to sand them out with the finer grits. Start with your coarsest grit, spreading further out with each finer grit. Or resand the entire surface, checking it with raking light between grits. Don’t be daunted, the second time will be faster, and your effort will shine through the finish.
