Touch Ups and Partial Refinishing

[Slight Return]

I'm trying to touch this up. As you can see the worn part goes through the color coat:





It's not a huge area, but I'm wondering how I can blend this in with the surrounding finish.

I do have nitrocellulose lacquer and a spraygun, and can get some black pigment to mix up. I also have some of the Behlen blush eraser, which I think is Butyl Acetate, which I've heard can help flow out nitro for spot repairs like this.

However, I'm not terribly familiar with using Butyl Acetate and don't want to make a bigger mess out of this than already exists (I don't know if that stuff is even necessary for a job like this).

I've been racking my brain over how to approach this one and I've got nothing. I'm assuming black nitro is probably the best option here, but is there anything else I could do?

I'm figuring I could spray black lacquer around the area after taping the top and back off to protect from overspray, but I'm not sure how to blend the edges of the partial refinish in with the rest of the finish. And how far around the damaged area I should refinish.

The worn areas feel pretty smooth, by the way. They don't feel recessed, like if you run your finger or nail over them, they just glide, if that information helps any.

How would you guys approach doing a touchup like this?

[Truckjohn]

Any idea what this original finish is? Nitro or poly?

Thanks

[redir]

You will want to test to see if it is nitro. If it is then a can of Stew Mac black nitro will touch that up nicely. If it's poly then I would probably dye shellac black and brush and or French Polish it in.

[mirwa]

Black is never black.

Sorry about the confusing statement, I can match a red or a blue or even a pink polka dot surface far easier than a black surface.

Must be close to a thousand shades of black that exist out in the guitar market IMO.

Before starting advise the customer that youcan make it smooth and coloured but no guarantee on exactcolour match.

From the picture and the visible wear I doubt it's a nitro more like a poly or an acrylic finish.

If they are happy then any spray can black followed by a clear coat

Steve

[mirwa]

I did not mention the repair in my reply,

tape the top and back, smooth the damaged area out 2 inches past each side of damage, shellac the exposed wood, smooth sand and follow up with 4 coats of black, allow to dry wet sand smooth respray any rub through if required and follow up with one or two coats of clear

Steve

[Slight Return]

First of all, thanks for the expert advice. I really appreciate this a lot.

Sorry I forgot to mention that it isn't nitro! Slipped my mind.

I'm not sure if it's poly or acrylic but it's a recent guitar so I'm positive it's not nitro.

But: Any safe ways to test if it's nitro or not, if only for future reference?

I've never used shellac before and I have a feeling I'm missing out on a lot because of that. Now could be a great time to learn.

When you say "dye," do you mean liquid stains? Like Transtint? Are these the only types of dyes that will work with shellac, or can you use pigments/powders? I have some Transtint dyes on hand and if those would work with shellac -- and be opaque enough -- that would be great.

Just one more question:

When you say follow up with coats of black, you mean with shellac, right? And you can use clear shellac as a finish once everything's done?

Or do you mean use the shellac as a base, then black nitro and clear nitro over that? Or black shellac and clear nitro?

I feel like this should be obvious and as redir pointed out, it could all be done with shellac -- just confused if there's any interplay between shellac and nitro I should be aware of, or are if there any inherent issues with using *only* nitro or *only* shellac.

Thanks again so much for the help. I don't want to be asking too many questions but finishing is my weakest skillset at the moment and I'm just trying to wrap my head around it. Trying not to overthink it!

[mirwa]

I use shellac basically as a pore filler, (sets a base for your paint).

Then follow up with a black acrylic / nitro or poly, if its nitro all these should apply just fine. Then clear.

I do most of my shellac work as a two pound cut.

Steve

[Slight Return]

Originally Posted by redir

You will want to test to see if it is nitro. If it is then a can of Stew Mac black nitro will touch that up nicely. If it's poly then I would probably dye shellac black and brush and or French Polish it in.

I have Renaissance wax. Would something like Meguier's 7 mirror glaze and then some Renaissance wax over the shellac finish be enough to protect it? Do people need to be aware the area is refinished with shellac, so they won't accidentally damage it by spraying and rubbing cleaner on it or something?

What do you think of using shellac as a base and color coat and then clearing with nitro instead of using wax as a protective coat over the shellac?

It sounds like color touchups in smaller areas might be easier with shellac than spraying nitro, since I could apply the shellac by hand. And then clear with nitro. Is this a misunderstanding on my part or could this work?

Originally Posted by mirwa

I use shellac basically as a pore filler, (sets a base for your paint).

Then follow up with a black acrylic / nitro or poly, if its nitro all these should apply just fine. Then clear.

I do most of my shellac work as a two pound cut.

Steve

Thank you! I have my little finishing book handy. I raised an eyebrow at "two pound cut" until I read that that means 2 ounces of shellac to 8 ounces alcohol, or a 1:4 ratio.

I'll pose the same question to you: what about dying the shellac and using that as a base coat and color coat, and then clearing with nitro to seal everything to the point where I can buff it out?

My only concern with spraying colored nitro is that if the black doesn't match too well that I'll end up spraying a much larger area with that off-black than I would with hand-rubbed, dyed shellac....what do you think?

And if using shellac as a base coat, I feel like I could kill two birds with one stone and get the black color down with it too, before clearing with nitro.

Sounds like preference comes into play here too, and there's more than one way to skin a cat. I will probably order some dye and shellac soon (I already have some clear nitro and some pigments and some sprayguns handy), and maybe post back later if I take a stab at this and run into any other issues.

Thanks again!

[redir]

Someone can correct me if I am wrong but I don't think Nitro over Poly works though for such a small touch up it probably would be ok. The beauty of nitro is that it melts into itself and becomes one homogeneous substrate. Poly doesn't nor will nitro melt into poly. It will layer on top of it and as such when you try and level it out you will have visible lines that outline the nitro fill.

Shellac is known to pretty much stick to anything and it too will melt into itself. It can also be applied very thin so the edges are easier to hide. It's never easy to do this stuff. Some people are really good at it, I never was, but sometimes I get it right real good. IMHO shellac by itself is fine and if the guitar is for a friend then you could mention it to them if you want, the only issue would be that if they touch the shellac area with alcohol it will dissolve. Otherwise it will be fine.

But if it's nitro then by all means melt in a nice top coat of nitro over the whole area once you get the color right and polish it up. Mirror glaze is fine, wax is not really necessary but okay too.

Sad is the day that guitar companies decided that the ease of use and expense of poly was better than nitro

[Slight Return]

Thanks for the reply redir.

Trying to be easier on myself here, as I agree completely with you: it's never easy to do work like this.

Sounds like alcohol is to shellac as lacquer thinner is to nitro. I'm planning on picking up some Everclear and some shellac flakes, and trying some black Transtint dye.

I'm assuming mirwa mentioned using shellac as a basecoat so the nitro will have something to adhere to, if it's true that nitro will not go over poly very well.

If that's the case I'm going to see how good I can get it to look with shellac and have some nitro ready to shoot over it afterwards if necessary.

[John Arnold]

My experience is that nitro goes over polyester just fine. It is a mechanical bond, so it's best that you don't sand the poly too smooth. 320 or 400 is smooth enough.

[redir]

Originally Posted by John Arnold

My experience is that nitro goes over polyester just fine. It is a mechanical bond, so it's best that you don't sand the poly too smooth. 320 or 400 is smooth enough.

Is it the other way around then that is the problem?

[John Arnold]

Correct. What you want is for the topcoat solvent to have no reaction with the basecoat. Polyester is impervious to lacquer thinner.

[redir]

Ok, I always get things backwards. Well there ya have it Slight Return... Good luck!

Thanks John.

[Slight Return]

Hey guys!

I ended up using the Stewmac Colortone black pigment in Behlen stringed instrument lacquer....and it was not dark enough. It was just "set" at the color it came in, which looked more deep charcoal gray than intense black.

I had a feeling that Transtint dyes might be able to "build" in intensity, because of their transparent nature. And it worked like a charm. I mixed some black Transtint dye into a roughly 50/50 mix of lacquer and lacquer thinner, loaded it in my HVLP gun, and started spraying, and it immediately darkened the pigmented area into a deep, rich black, which matched the rest of the guitar.

Of course I had the whole body taped off and newspapered and all that to keep overspray away as much as possible on the top and back. I decided to refinish almost the whole side. I forgot to mention that there was another damaged area closer to the endpin, which also affected my decision to refinish the whole side.

The black Transtint matched so well I figrued it'd be really hard to tell the difference between where the refinish ended and the original finish began, and refinishing more of the side seemed like it would make blending it easier.

I ended up leaving the pigment coats on, and just sprayed right over it, because I wanted to have plenty of coats anyway, to make sure I didn't accidentally wet sand and/or buff through to the wood. During some of the later coats I ended up going more to a 60/40 ratio to build the clearcoats up.

I let it sit for a week and a half for the finish to cure at least a little bit, then wet sanded with some Wool lube and distilled water at 1000 and 1200 grit. Then moved to some Meguiar's products and a drill with a foam buffer:

Ultra cut compound, Fine cut cleaner, Swirl remover 2.0, and then finished with #7 Mirror glaze.

There were still some fine scratches left. I've got a lot to learn when it comes to wet sanding and buffing, but I think it looks better than it did before, and I'm relatively happy with how it came out.

I just didn't want to go too crazy with correcting those mistakes, for fear that I'd wetsand or buff right through to the wood and have to start all over again.