Well, disappointingly, the desk top needed a complete re-sanding. In the higher temperature conditions late yesterday afternoon the finish did not flow well and left an unacceptable orange peal surface. The orange peel was just too rough, another coat wouldn’t help. the other parts were quickly brought to smooth with a 220 grit rubdown.
I sealed the desktop’s new surface with shellac, which dried very quickly; warm today. Knocked down the nibs, and shot a coat of thinned poly. I appears that it’s critical for proper atomization with these HVLP guns to have a consistency in viscosity, and that needs to be thinner than I usually use for spraying. This will necessitate ordering a viscosity cup so I can test small batches of finish.
Normally with small projects, I only mix 2-3 ounces of finish. That’s about the minimum that you can test in a cup. I don’t know if you are all familiar with how a v. cup works. An appropriate thinner or reducer is added to the finish, mixed, and then poured in to a viscosity cup. The time in seconds that it takes for the finish to drain completely from the cup indicates the viscosity of the finish. After some trial and error testing, a record of results will build a table of thinner/finish mixes which can then be adjusted for temperature and humidity. Short answer: finish needs to be thinner. (Can’t seem to find one locally, so will rely on the internet. Really strange that Paint stores and Auto Supply stores wouldn’t have one, but that’s the case).
I was very impressed with the reduction in over-spray. The literature on the gun indicated a nearly 85% transfer rate; which means only 15% is lost to the atmosphere. Compared to standard sprayers (40%) I did expect some improvement. I was pleasantly surprised with how little of that usual surrounding cloud of vapor was evident. Odor was greatly reduced also.
Today’s weather was the same as yesterday, cool in the morning and warming to the mid 70s in the PM. I adjusted the mix and applied a nice thin coat of semi-gloss poly to the top, desktop, drawer, supports, and base. I am very pleased with the result today. The top, supports, drawer, and base are finished and ready for the rub-out waiting week. The top will need at least one more coat, possibly two. I expect to get to that tomorrow. Weatherman says cooler with a slight chance of early drizzle. Hmmmmm, looks like I’ll need to adjust my thinner ratio again.
I am not aiming for a filled semi-gloss finish. This piece was constructed from a large billet of walnut that I scavenged from a farmer in Pasco, WA, and some wormy oak that had been milled from a dead tree in North Dakota and brought out here a few years before. So there are interesting spots and various colors throughout the piece, but I wouldn’t claim it as really fine furniture.
I anticipate posting pic’s when it is complete. I haven’t taken the time to make a record of this process, since I am basically just refinishing an older piece. I’m sure the LJ’s will let me know what they think when they see it.