MIMF

I’m almost finished with my first build(s): two more-or-less identical OOO-12 frets made from some nice quilted cherry I got from a local saw mill and a sitka top. My question is about how to safely level the finish before working my way up through finer grits. As you can see in the photos, the first one has been completed (and, by the way, I'm really happy with the way it sounds - bright and articulate, like some maple guitars I've played). I brushed on about about 6 coats of KTM-9, following directions, and let it cure for over a month. I tried sanding with 400 wet/dry paper on a foam block with soapy water, but in spite of using what I considered a pretty delicate touch, soon began to cut all the way through the finish. I got scared and switched directly to “micro mesh soft touch finishing pads” 1200-8000 grits, then a foam pad on a drill with rubbing compound. The results are not surprising – a glossy finish full of bumps and ridges. It's more noticeable in person that in the photos.

Any suggestions to help me achieve a smoother finish on #2?

Thanks,
Dave

I tried sanding with 400 wet/dry paper on a foam block

Bingo! Use a hard rubber block for the leveling. Erasers are great, especially the huge 'joke" erasers. Cut one up into usable sizes, and you'll soon enjoy nice, level finishes. The foam block "gives" too much and follows the bumps and dips of the finish, instead of cutting through the high spots.

Also, look around the web, or the archives here, maybe, for a "grit comparison chart". Micromesh has a different grading system, where their 1800 is rather more like 320 or something. Then there's the differences between P grits and CAMI/ANSI grits. There are some BIG differences, that matter a lot to us.

400 grit is too coarse for leveling of the final coats. This is why you sanded through the finish. Your sanding between coats should already have you in the ballpark of being level. And so you could start sanding the final coats with some where above 600 grit.

Definately go with the pink-eraser as a leveling-block. I prefer cork (over foam) as a backing once you've established a level surface and you now are just working out the scratches to a gloss. I usually start with 800 (P-grade) to see if I can get away with starting there. The scratch-pattern is very shallow which makes it a few extra strokes to level, but I feel it's faster and safer than making coarser-scratches and then working-up the grits to remove the scratches. If it's not working fast-enough, you can move down in grit until you're getting the progress you're looking for.

As you get more experience, you'll be able get there faster by being more agressive with the coarser-grits and know when to stop before you do more harm than good. For now, play on the safe-side. It takes much longer to start over and refinish than to sand a little longer.

Thank you, all, for the suggestions. The eraser trick makes sense, and I like the price. Also, something was telling me that those grit numbers don't always mean the same thing, especially when one is dealing with different types of products. #2, here we go...

Dave

On my first build I used micromesh only and after burning through the finish here and there I did more spraying. After a couple more small burn-throughs I got some very good experience doing drop fills! My experience (and patience) have improved much in the year and a half since then but I learned a lot. Nice looking effort for your first build too.

+1 to what Barry said. How much level sanding did you do between coats? I do oil finishes with many more coats, but a similiar technique should work with what you're using. Start level sanding (dry with a block) with 600 or 800 after the first or second coat (because the finish is still thin, 400 will burn through too easily). After the third or fourth coat, move back to 400 or 600, getting rid of all the shiny spots is the goal. The better job you do of level sanding between coats really shows up when you start leveling the cured finish.
By the way, that looks pretty good in the photos!

Hi everybody, I'm just reading this tread and I'm finding it hard to understand why there is so much sanding going on. Maybe I'm doing something wrong but most of my level sanding is done before I start spraying and when my finish is cured I just wet sand with 1500 grit W/D and then buff to a high gloss no sweat.

It depends on what kind of finish you're using. If you're spraying Lacquer, then it all flows and melts together and is very forgiving. If you're brushing Lacquer, or spraying anything else, then you will need to even things out unless you have the best spray-skills in the world.

When I'm "sanding" the finish, I'm not putting any pressure as I skim the surface. I'm only hitting the high-spots, almost not even touching the surface. This only to fix a drip or run and smooth any sandy-textures.

If all is going well, then there is no need to sand.

...then buff to a high gloss no sweat.

Wow, I'm jealous John! You may very well be the only person on the planet that does not struggle with finishing!
I know I do!

Well, between spraying shellac and drinking rosewood juice I'm not surprised!
I Thought I knew a lot about finish when I started building guitars, I did custom paint on motorcycles in the late '60s, and I've done a lot of furniture. Guitars are different

Well Chuck,as I say maybe I'm doing something wrong but all the Guitars I've built after the first few when I was learning how to apply a sprayed finish ( water based ) have turned out great. Why would you struggle ? it's just one more part of building a Guitar that has to be mastered, it's about the only part of Guitar building that can be "fixed" if you are not happy with the finish scrape it off and start again.

I have been finishing furniture and guitars for almost thirty years now. I learned from an old master finisher who learned from his dad and grandfather back in New York where they built custom ordered reproducton furniture.

First, forget wet or dry sand paper. Please don't be offended all you wet or dry believers but (in my experience) wet or dry is like using an old 80s apple computer rather than what's available today. Slow and low tech. There is a lot better stuff.

I gave up wet or dry papers twenty years ago and now I use all 3M paper, 220 and 320 grit Gold 216U for all sanding-- bare wood and between finish coats and 800 grit Gold 216U and then 1200 grit 260L for leveling the finish before buffing.

There is nothing gained by sanding the wood or between finish coats with anything finer than 320 unless you are doing an oil finish. You need the sealer and lacquer to have something to grab onto. The scratches you make in the lacquer between coats should be deep to help the successive coats burn into to each other well.

Here is my scedual I have used for the last 25 years on guitars.

1- Final sand bare wood.
2- One coat of sealer.
3- Apply grain filler(if using open grain woods) let cure for at least 24 hours.
4- Remove excess grain filler by first wipping most of the residue of with medium/maroon Scotch Brite/woven abrasive and then sand lightly with 220 or 320.
5- Another coat of sealer let dry for one hour. Apply toner/color coat if wanted. Let dry for another hour.
6- Three coats of finish, brushed or sparayed. let cure till next day.
7- Scuff sand about 75% to 80% flatwith 220 or 320 ( I use 220) and then apply three more coats and let core till nexy day.
8- At this point sand the finish flat until ther are no clossy spots (no further) and apply three more coats to back & sides and only two more to the top.
9- On the same day apply two more light coats around the edges of the head and the edges of the body about 1/2" in from the binding. The edges are where you are most likely to sand through when leveling before buffing.
10- Let cure for two weeks to a month depending on the type of finish.
11- Sand the entire guitar 95% flat with the 800 grit 216U. Complete the leveling with the 1200 grit 260L. By the time you completely level the finish with the 1200 you will have removed the 800 grit scratches.
12- Buff.

Works Great.

Joel

Joel, that is similar to my finish schedule. And I agree with your comments on sandpaper.