Sanding my Brushed Nitro finish

[TonyinNYC]

Here is another series of pics on wet sanding, this time it is on a brushed nitro finish. It was requested that I shoot a video, but I don't know how to edit, so it is a lot of me sitting there with my hand going back and forth over the guitar. Spray a little water, sand a little more. Dry, check progress, repeat. If anyone really needs, I mean REALLY needs to see a video to hear me explain some of this, I suppose I can make one, but the pics here should get you going in the right direction. It is also harder to pick up the scratches on video versus a still shot.
Lets begin, shall we?
Here we have a picture of the finish on a claro walnut back. Shiny but uneven.

Look closely and you can see little dots on the surface. Those are pores. Yes, I filled them, but I don't always get them all. Please don't be critical. Moving on, the finish has been on this guitar since I made the first video here:viewtopic.php?f=25&t=431
About three weeks have passed since I applied the finish. One thing I noticed about brushing is that since the finish goes on pretty thick compared to spraying, it takes a lot longer to dry. That means if you sand it too soon, your finish will continue to shrink as it dries and reveal pores or gaps you could not see when you finished sanding.

Here is a shot after I have started sanding.


You can see that the surface is not shiny any longer and you can also see some scratches from the paper. I was using MicroMesh when I started sanding but it was taking forever and I wanted to show some progress so I switched to 320. I would NOT recommend for anyone to use 320 to wet sand your finish unless you have done this before, your finish prep was excellent, and you check your progress very often. If you sand too much with the 320, you wont have enough finish left to sand out the sanding scratched left by the 320. Trust me.
Here is a pic after sanding with 320 for a short time:


The finish is really beginning to level out, the "dots" from the pores are gone, and I will be able to switch to a higher grit very soon.

I am about half way to where I want to be before switching grits in this shot:


Still a lot of shiny areas left, but you can see I am making progress.

Here I have wet sanded half of the back only with 320 grit. See if you can spot which side has been sanded:


Did you guess it was the right side? WINNER!!! Notice I have not completely removed all of the shiny spots. I want to leave enough lacquer on the guitar after the 320 so that I can sand out the scratch pattern with the next grit.

My process has evolved since I brushed my first guitar. I used to only sand in a circular motion with each grit. The problem with that is it becomes hard to tell if you have completely removed the scratches from the previous grit as you go up in grits. I now sand differently with each grit which is something I am only just trying on this guitar for the first time.
I am sanding with the grain using the 320 grit, then I am going to sand across the grain with the next grit, which will be 600, or MicroMesh 1500 if I am out of 600 wet/dry. I have already tried a small patch and it seems to work great! You can really see the cross hatching where you have not sanded enough. Too bad this doesn't work as well on bare wood!
I should have more pics tonight as I move up in grits.
Be especially careful when sanding near the edges of the box. It is really easy to let the sanding block tip over the edge and sand through the lacquer.
Another key point is that the harder and bigger the sanding block you use in your prep, the flatter you can get the wood. When you are wet sanding, the same applies, and will result in a smoother, flatter, more glass like finish. A small, soft block will result in a less even finish. I still dont trust myself to use the same block I use to prep the wood for wet sanding. I use the foam block that came with my MicroMesh kit.
Hope this has been helpful. More pics and info to follow as I move up the grits. I only started wet sanding this box last night, so bear with me as this will take a while!

[Dave Bagwill]

Thanks for stepping up and posting, Tony. You've got true grit.

[ken cierp]

Not seeing any pictures???

[TonyinNYC]

Picture links fixed. I used the wrong link from flickr to post. My apologies. I also added a pic I had forgotten when I first wrote the post.

[TonyinNYC]

More info, but still no video.
My idea to sand perpendicular to the last scratch pattern when I changed grits has worked out very well. Normally, I will end up with one or two spots that need attention to remove some scratches I missed that only show up when I begin polishing. I think this technique will eliminate that problem. I made a jump in grits from 320 to 600 and sanded across the box instead of tip to tail. You can see I still have some scratches left to remove. Sorry for the big pic, but it's hard to see the detail in the smaller pics.
In this pic, I am about half way through sanding with the 600 grit. The scratch pattern is running in both directions. One way from the 320 and perpendicular to that with 600, not that you can tell a difference in the size of the scratch.


In this pic, I thought I was done with the 600 and I could switch to a higher grit, but upon closer inspection, I see this:


In that pic, the scratches going up and down in the pic are from the 600 grit. The curved scratches that go left and right are from the 320. More sanding is needed!

I thought I could give some tips and warnings along the way, so here is a tip about the pic below and how to deal with the parts that are not yet level correctly, particularly because they are at the edge of the box.


Avoid the temptation to sand a bit more aggressively. It would be easy to push on the paper with some pressure to get those areas level, but if anything, use less pressure in this area to avoid sanding through your finish.
In general, you should use a very light touch when wet sanding. I use almost no pressure and I let the paper do the work. The result is a nice smooth, glassy finish. I still have a ways to go to get there, but I am working on it.
My finishes look good, but I see the flaws that maybe nobody else does and it drives me to work harder on each guitar I finish. Every little bit of info helps to get a better finish.
Questions are always welcome.