Acoustic Guitar Construction

I finished my latest guitar with Watco spray cans. Originally, I thought I'd finished spraying, and had begun sanding. It was then, while sanding the back with 600 grit wet paper, that I finally understood what I was looking for about leveling the surface. I finally got it. And, I was very happy with how well I had done.

However, on the top, I had only put on 2/3rd's of the number of coats that I had put on the back and sides. Aware of that, I sanded a bit more gently. Most that was not level was around the edges. But I was sanding the edges, and still going up into the body. Well I went too far and went thru the finish on the top in an area around the bridge. Not a big area, but sanded thru none the less.

So I ordered 2 more spray cans of Watco, and used them both up spraying not only the top but the back and sides again as well. Then I let it cure.

Last Sunday, I started wet sanding my guitar body again, starting with 600 grit up to 1500 grit, then with micro mesh from 4000 to 12000. Then I used the 2 finishing bottles that Ken recommends.

After doing the 600 grit, I looked at the body, and it looked flat as the top of my desk. I mean it's the best job I've done so far on leveling.

But once I put on the Wizard's Finish Cut and Shine Master, I was expecting this thing to be the absolute best guitar shine in the world.

I was sorely disappointed. I don't see reflections as sharp as I expected to get. And my concern is that I did something wrong somewhere.

Now, one thing I see, is scratches everywhere. My wife couldn't see them, but when I angled the guitar just right, mostly on the sides, I could see them. The cloths I use to put on the finishes are from an automotive store for waxing, etc. They're very soft "micro fiber" cloths, and I didn't think they left scratches.

Think it's possible I left the scratches from a long time ago? They all seem to run with the grain. And after each grit of paper and mesh, I rubbed along the grain.

It's not a terrible job by any means, but my expectations were extremely high, and thus the disappointment even greater.

If any of you have any ideas, I'm all ears.

I know many feel my pain,
Bob

Yep -- you got it right, if you don't remove every single scratch as you progress it will surely show up as a flaw after polishing, actually amplified. But if this is an entire area that appears cloudly, dull and even -- a grit may have been skipped or a rag used to wipe a course grit, could have been used to wipe off a residue from a finer grit -- this is a common mistake and often over looked --- you must use a seperate wipe rag for each grit, preferably a clean rag.

I will tell you this -- I bet your finish is every bit as good as any first or second or even third timer's. When looking at finish work -- I am careful not to unrealistically compare it to what the Martin factory can produce --- they have been at it for 180 years, give yourself a break.

Bob, I definitely feel your pain. I'm on my 3rd guitar, and I'm still in deep-learning mode. I have achieved a nice shine on the latest, but yes I can still see swirls/scratches in the finish. In my case I think that was partly caused by the small hard bits of finish that occasionally accumulate on your sandpaper, so you are scratching the finish with those, and not from the sandpaper itself. The remedy (I think) is to make sure you use plenty of water with a bit of soap, look for those bits, and change paper often.
By the way, for my final sanding I used 800 grit paper to start with. I don't know if 600 is necessarily a problem, but I think if your finish doesn't need leveling then 800 is okay to use.

After I used 800, I went to 1000/1500/2000, and then used automotive compounds. Basically turtlewax polishing compound, then Meguiar's scratch x2.0, followed by Autoglym wax. Like Ken says, each step with a different applicator and wiping rag.

For me, to improve on this I'd need to buy the buffing motor on a stand.

Bob,
I re-read your post

After doing the 600 grit, I looked at the body, and it looked flat as the top of my desk. I mean it's the best job I've done so far on leveling.

But once I put on the Wizard's Finish Cut and Shine Master, I was expecting this thing to be the absolute best guitar shine in the world.

Maybe a typo? But "Finish Cut" takes out scraches 1200 grit and finer -- if you stopped at 600 that may be part of the explaination.

Oh, no, Ken. I did not stop at 600. I continued with 800, 1200, 1500, then went to the micro mesh from 4000 up to 12000. Then I did the Finish Cut and then Shine Master.
I washed all my "micro fiber" cloths tonite, and will set them up to use one for each grit as I go back. Looking at the back, it seems pretty good now. I could see pretty good definition of items in the reflection. I'll try to take a pic tomorrow morning (I get to work from home on Thursdays now - but have to travel to a meeting by about 10:30 or so), and I'll post it. So I'm in a better frame.
I think I'll put more thought into sanding, and watch my results with each grit better.
I probably did not take out the scratches, as was said, when I went to finer grits. I probably rushed things.
I'll try hard not to over-react though, but just be sensible and see what I come up with.
I'd hate to sand thru the dang finish this time.
If mistakes are good teachers, then I'm not being cheated.
Thanks also, Ken for the words about giving myself a break. That helped.

Yes Bob, don't be too hard on yourself. I'm on my 16th and I still am struggling with this issue. My latest attempt did work out the best till now. Starting with 800, 1200, 1500 and 2000. Do not rush the finer sandings! 'Cause that was the major flaw in my former builts. After that I use now 3M perfect plus 3 extra fine polishing paste (No. 80349). This rubbed with a 3M yellow pad on my drill. Easy and almost perfect.

What I learned in the past years is not to try to make the laquer too thin in the first place. If the prep is not 100%, as we amateurs have, the extra space for sanding and rubbing is a welcome thing all the finishing stages.

Sanding though the finish is soooo annoying!

Herman

What I learned in the past years is not to try to make the laquer too thin in the first place


Bingo!

The number one finishing mistake is not putting enough on in the first place -- shame of the so called experts that needlessly warn of heavy coating doom and gloom. They are only repeating the mythological nonsense.