Touch up finishing help

[Fiestared]

I removed the wraparound bridge on my old ibanez and drilled holes for a tune o matic. Now i have some bare wood from the plugs and som finish chips. I know hiding this might be impossible for someone like me, i am a player not luthier but would of course like to do it as best as possible. I have some black spray paint. Any tips? 

[Bizman62]

First, you've got a good start as the grain direction of your plugs matches with the body!

For a level finish you'd need to fill the pores of the plugs. If you can, try getting the plugs a bit lower, approximately the same amount as thickness of the original paint layer. A similar plug with a piece of sandpaper glued onto the tip, attached to the jaws of a pillar drill might be accurate enough. Some dishing at the edges is required but not much, that can be done with a finger and sandpaper. Apply the filler and resand just below level. Apply the black, I guess a small brush might be even better than spraying for such tiny areas. Black nail varnish might be a better choice than spray paint. Sand flush to a satin matte. Apply a coat of clear, sand level and buff. Something like that...

 

[Fiestared]

24 minutes ago, Bizman62 said:

First, you've got a good start as the grain direction of your plugs matches with the body!

For a level finish you'd need to fill the pores of the plugs. If you can, try getting the plugs a bit lower, approximately the same amount as thickness of the original paint layer. A similar plug with a piece of sandpaper glued onto the tip, attached to the jaws of a pillar drill might be accurate enough. Some dishing at the edges is required but not much, that can be done with a finger and sandpaper. Apply the filler and resand just below level. Apply the black, I guess a small brush might be even better than spraying for such tiny areas. Black nail varnish might be a better choice than spray paint. Sand flush to a satin matte. Apply a coat of clear, sand level and buff. Something like that...

 

Thank you so much for your answer. It might be having a hard time lower the plugs but I can try. Maybe black nail varnish is a good idea as you described. If I colour it black, when you say sand level, what grit would you recommend, and is it possible to wet sand with 2000 or so over thd edges, so touching to old finish aswell or will that make scratches?

[Bizman62]

You don't have to lower the plugs much, some 1/5 of a millimetre should suffice. If you don't want to build a tool, a narrow strip over your finger should do the trick. I'd start with 180 and go to 400 before filling, then go from 240 to 400 before painting. Depending on how bad brush streaks you get, sanding from 240 or 400 up to 2000 before the clear coat and after that the same. When sanding a finish, make a 45 degrees turn at every higher grit and sand until the previous scratches vanish! Another rule for sanding is to never force the paper as that would only create balls of loosened grit and lacquer dust which will dig deep grooves. You simply can't make the paper cut deeper than the grit's height which is measured in micrometres.

And yes, after you've got finish over the bare wood you can use wet paper and another yes, sand the old finish over the edges. If your hand slips simply sand that area with finer grits turning 45 deg every time you change to a finer grit. The goal is to get an almost shiny matte surface - 6000 grit isn't glossy yet but compared to the scratches you have there it will look like perfect! The final touch can be done with a rubbing compound. Basically you can to use a regular coarse paste like Biltema Rubbing 36-629 already after 2000 grit wet and a swirl remover like Biltema Polish Premium 36-84 after that. Use the pastes all over the top to make the gloss uniform.

[mattharris75]

The good thing here is that if your repair isn't perfect some of it should be covered by bridge and strings, so it shouldn't be particularly noticeable. 

[Fiestared]

32 minutes ago, Bizman62 said:

You don't have to lower the plugs much, some 1/5 of a millimetre should suffice. If you don't want to build a tool, a narrow strip over your finger should do the trick. I'd start with 180 and go to 400 before filling, then go from 240 to 400 before painting. Depending on how bad brush streaks you get, sanding from 240 or 400 up to 2000 before the clear coat and after that the same. When sanding a finish, make a 45 degrees turn at every higher grit and sand until the previous scratches vanish! Another rule for sanding is to never force the paper as that would only create balls of loosened grit and lacquer dust which will dig deep grooves. You simply can't make the paper cut deeper than the grit's height which is measured in micrometres.

And yes, after you've got finish over the bare wood you can use wet paper and another yes, sand the old finish over the edges. If your hand slips simply sand that area with finer grits turning 45 deg every time you change to a finer grit. The goal is to get an almost shiny matte surface - 6000 grit isn't glossy yet but compared to the scratches you have there it will look like perfect! The final touch can be done with a rubbing compound. Basically you can to use a regular coarse paste like Biltema Rubbing 36-629 already after 2000 grit wet and a swirl remover like Biltema Polish Premium 36-84 after that. Use the pastes all over the top to make the gloss uniform.

Thank you again for your answer! Two questions, what could i use for filler? I have some wood paste, would that work and how should i apply? Next question, maybe not professional but I have read that one can use toothpaste for polishing afrer wetsanding, like a scratch remover. Yes or no?

[Bizman62]

For such a small area wood paste should be just fine. I've even heard of gypsum based paste being used on guitars. So basically anything that fills the pores without shrinking at a later stage should do. The layer needed is so thin you don't have to worry about any cracking caused by shrinking. Just slab it there with a spatula and when it's dry, sand it level with the surface.

Tooth paste is slightly abrasive and since you most likely already have it at home there's no harm in using it. I suppose it would be as gentle as swirl remover. And as @mattharris75 said a less than perfect repair should be hidden under the bridge and strings.

[Fiestared]

16 hours ago, Bizman62 said:

For such a small area wood paste should be just fine. I've even heard of gypsum based paste being used on guitars. So basically anything that fills the pores without shrinking at a later stage should do. The layer needed is so thin you don't have to worry about any cracking caused by shrinking. Just slab it there with a spatula and when it's dry, sand it level with the surface.

Tooth paste is slightly abrasive and since you most likely already have it at home there's no harm in using it. I suppose it would be as gentle as swirl remover. And as @mattharris75 said a less than perfect repair should be hidden under the bridge and strings.

Ok! Thanks! Would you recommend that i mask the area around the plug with tape when i paint and sand or not? Without it seems easier to make it smoother with the surrounding but harder to sand withour touching the original finish around the plug...

[Bizman62]

As you say, without masking the surrounding is easier to sand. If you want to mask the area, leave about 5 - 10 mm around the plug unmasked so you can smoothen the edge. You're aiming to a shallow bowl, not sharp edges. See image:

[Fiestared]

On 3/30/2021 at 2:24 PM, Bizman62 said:

As you say, without masking the surrounding is easier to sand. If you want to mask the area, leave about 5 - 10 mm around the plug unmasked so you can smoothen the edge. You're aiming to a shallow bowl, not sharp edges. See image:

Thanks ! I made the effort and borrowed a drill press. Filled lighlty with wood paste. Now i have made a first layer of black. Looks ok but will have to even out brush strokes so probably have to paint 2 or 3 coats of colour. How long should i wait between sanding? And recommended sandpaper grits between coats? And when I am "satisfied" could i use fine paper on the whole area / surrounding original paint to smoothen it out? What grit do you recommend and as you said maybe some scratch remover? Is that applied before or after wet sanding? I noticed they sell scratch remover with color, is it better to use without color since the scratches are in the clear coat? Many questions.. thanks again for the help!

[Bizman62]

Whoa! That's a lot of questions you got there!

There usually is some advice on the paint can but if not, I'd recommend to wait overnight before sanding. Between coats some 400 wet should be good. Wipe the dust off!

As you said there's a clear coat on top you'll have to enlarge the shallow bowl a bit so you'll apply clear on clear. The grey marks the new black, the blue is old clear and the  lavender is the new clear:

After you've got the patch level with the surrounding you can sand up to 2000 wet a bit past the patch as I instructed up there. The scratch removers are finer abrasives than any papers so they come last. The fine scratches don't necessarily require any sanding before using the paste but if you want to, you can try the two finest wet papers all over the area. Most likely it's not worth the effort, though...