DO NOT give the car polish a try until you have tried it and experimented with it. I'm sure I don't have to tell ya how I know this *L*
Thanks, Bill, but I've been using this Meguiars on guitars for over 30 years. Works great!
I've never heard of using such fine grits. I would use a card scraper to get a near perfect, high gloss surface. All that sanding has got to raise the grain, and you're going to lose a LOT of wood in the process. A card scraper requires a bit of practice, but makes a beautiful surface.
The sanding isn't raising the grain, Tom, because it's all under the shellac. I did use a card scraper when the back was flat and before the braces were glued on. The Micromesh
I have goes down to 12,000. I may not go that far but I have the option. At that point I can polish by hand without having to use a buffing wheel. Matter of fact, if I just go to 6,000 I can probably do the polishing by hand.
David... are you block sanding or just using your hands?
Block sanded the wood before the finish and using the same block now. No surprises that way. The only places not getting block sanded are on the neck in the small detail areas.
The Mahogany was sanded to 320 and then I used a card scraper. The shellac went on very smoothly but it still needs to be leveled if you want the pores filled, which I do. To fill the pores you can either use a pore filler - many different kinds available - or use the finish to fill the pores. I chose the latter. By applying the shellac and sanding it back down, then wiping the slurry across the grain, the pores were filled in no time. Each subsequent coat of shellac melts into the previous and as you keep sanding and taking the finish back down to a base level you finally reach the point where you can go to the finer and finer grits.
To add to what I replied to Dan
earlier on the drywall and the low spots, in retrospect it is very different. As Bill said on the wood having high/low spots, that's something I took care of in the bare wood stage. The back on this guitar is only 0.100" thick so you can't just go 'sanding crazy' once it's together. If it was the 3/4" top to a table I'd have plenty of leeway on getting the top surface flat but on this curved surface it had to be right before I glued the first brace on (the back has a domed 15' radius). Obviously there were some very minor areas that sanding and scraping took care of but before the first coat of shellac went on the back was flat (except for the dome radius...).
So where the difference comes in is that with drywall once you get the wall flat you're typically going to texture it and then paint it. All of that serves to hide any sanding scratches and minor irregularities. With the guitar and a high gloss, very thin, transparent finish that luxury of having a cover-up opaque finish is gone. Every irregularity will show. So all of the scratches have to be so small that they can't be seen.
Same with painting cars - once you get the panels flat and sanded to as fine as you want to go the car gets sprayed with an opaque paint that is usually not sanded before the clear coat goes on. And unless you're doing a show car the clear coats of today don't get sanded and buffed out to a high gloss. The clear coat just dries to a high enough sheen that further buffing and leveling isn't required. It may have a slight bit of orange peel but that's also acceptable in most car finishes, to a degree.
The final way that none of this is the same is the film thickness. Guitars are built to sound good, not just look good. The thicker the finish the poorer the guitar sounds. So I don't have the luxury of building coats to the point I'm so far away from the wood that sanding through is no longer a possibility. Nope, the finish is somewhere around 2 mils to no more than 3 mils thick and I don't want it to go any thicker.
Nitrocellulose lacquer is what I've used on guitars before and it's much easier. There's a lot of debate as to which sounds better but that's another topic. I'm using a French polish technique with the shellac more because I wanted to see if I could get the finish like I want. I know I can get it in lacquer.
Either way it's a fun build!