Friday, April 12, 2002

Mandolin #1: Finishing

After finishing, I'll be finished!



Applying the Clear Lacquer
I ordered four cans of Stew Mac's aerosol lacquer and was hoping to get 6 to 10 coats on the mando. For the first few coats, I hung the mando in the carport and coated the the whole thing. I would then bring it inside and hang it to dry. The problem with this approach is that, if not applied very sparingly, the lacquer tended to drip down the instrument, either creating runs on the surface or little hanging drops off the scroll or points. The other problem was that the burst stain coats, in addition to not having been fully absorbed into the wood because of the sealer, was lacquer soluble and thus would run along with the lacquer. For the most part, I was able to scrape the little brownish lacquer drips off the points and scroll between lacquer coats.   

After a few coats, I developed the more time consuming but consistent approach of apply coats to just one part of the mando and leaving it to dry in such a way as to minimize drips. I would hold the mando in a gloved hand and apply as light a coat as possible to the side I was working on and then rest it on the opposite side in my neck rest. The lacquer still settled a bit but at least there were no drips and the coat was more consistent. It was more difficult to use this technique on the sides but doing the treble and bass sides separately and propping the mando up on its side to dry seemed to work.

Laquered back 3 Laquered back 1

Laquered back 2 Drying side laquer 1

Wet Sanding
After 5 or 6 coats, I wet sanded with 400 grit wet/dry paper using dish soap as a lubricant. The wet sanding leveled the finish and removed any lingering runs and left a dull but consistent finish. In a few spots, the wet sanding removed lacquer that had obviously dissolved some of the stain. As a result, removing the lacquer removed the stain. I was able to touch up a couple of these spots around the f-holes using a stain pen although I had already rationalized that a "vintage" finish with some inconsistencies could potentially look intentional. Coincidentally, just about the time the stain was coming off the back of the neck, I decided that I wanted a "fiddle neck" with the finished rubbed off the back of the neck. I just kept going with the sand paper until I was almost down to wood right in the middle of the back of the neck. Enough of the stain had soaked into the endgrain that a nice flame was left.

Wet sanding 1 Wet sanding 2 Wet sanding 3 Fiddle neck

After the first wet sanding, I got a couple more coats on all surfaces (light on the fiddle neck) and went back with 600 wet/dry to make sure everything was as level as possible. Then a final very careful coat on all surfaces and a long fourteen days (according to the instructions on the can) while the lacquer cured. I recommend trying to time this period while you'll be away or busy or have two broken arms.

When the fourteen days were up, I did one more wet sand with 1000 then 1500. I had been looking into buffing wheels for drills and orbital sanders but thought I'd first try polishing by hand. I was happy to find that a couple swipes with a terry cloth pad and some 3M automotive rubbing compound followed by a clean cotton T-shirt left a mirror shine. Before I got things too perfect, I refitted the bridge to adjust to any changes caused by the finish. Then a complete polishing with rubbing compound and buffing with the T-shirt and I had one shiny mandolin. I had to ream the tuner holes a bit to get the tuner bushings back in the holes but the rest of hardware went on smoothly. A fresh set of J74 strings and...

Index of Project

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