MIMF

Hello all! I found some very helpful comments from a older thread, and was encouraged to start a new feed.

Customer requests a painting on his Takamine acoustic, cedar body.

Tattoo-outline minimalist style, creating a dreamcatcher from the sound hole and branching into an eagle near the base.

The office at a California distribution center said they used a light polyurethane for this model.

Customer initially was against sanding but I've gotten great questions and comments from the finishes thread which bring to mind how the substances will interact and adjust over time. I'm waiting on word as to whether the customer will allow me to sand back the entire panel, complete the painting (designed to convert the smallest amount of surface area possible), and refinish over everything to keep it consistent.

My final battle I believe boils down to process: for those of you who restore or have worked with "mixed media" instruments, what are your recommendations before I even touch this guitar?

I will have a full day to myself to complete the work and let it cure. He's moving north in less than 1 month so we decided to wrap this up to let it settle into it's changes as early as possible before traveling.

**The paint isn't going along the edge where a pick guard usually goes. There never was one^.~

Thanks!

A poly finish is one of the toughest to work with.
They are very hard, and will be difficult to sand to a point that you have a paintable surface.
I don't know your paint / art process, so I cannot comment on that.

To re-finish the poly afterward is not going to be easy, depending on what kind of poly it is.
Most commercial poly finishes are cured with a high power UV light.

What about using vinyl wrap material? This would leave the original finish unharmed.

Cedar is very soft wood so keep that in mind for starters if you need to pencil or ink the design in at the start. When Takamine says "light polyurethane" I'm guessing they tried to keep it fairly thin. Polyurethanes are tough but typically flexible and not terribly scratch resistant as compared to the more commonly seen polyester finishes on most factory built instruments. I'd do a very light scuff sanding with 1200 in a discrete area and see if your paints stay put as they dry. If the guitar has been polished with a silicone containing polish you may find that the paint just balls up or you get "fisheyes" where your paint migrates away from a spot. You'll have to wipe it down repeated with alcohol using fresh paper towels until the traces are all gone. Takamines aren't terribly refined instruments (though some were quite expensive) so I wouldn't hesitate to go at it as you see fit. Your clear-coat choice is going to depend on whether the owner intends to keep playing it or hang it up on the wall as art. If it's survived thus far without a pick guard then perhaps his style is not too aggressive and a few sprayed coats of rattle can Krylon clear will keep it intact. If you have an airbrush then you might go with the General Finishes Enduro-var which sands easily for the first day or two and can build up quickly. That said it specifically instructs us to use it on bare wood. I wouldn't worry about that as it has always adhered well for me over painted surfaces and marmolium.

Everyone has been fantastic with advice, thank you very much!

From what's described here, I'm going to offer the customer 2 options: to work with the current surface and deal with potential inconsistencies with adding finish, OR allow me to smooth over the design area with (thank you David and Gordon) a superfine grit so that the total end result is smooth.

Barry Daniels wrote:What about using vinyl wrap material? This would leave the original finish unharmed.

I don't think I'll be able to set up a vinyl in time for his deadline, I'd end up recommending someone else for the commission>_< Great future goals, though!

Whether the paint will bubble or not shouldn't be a problem, it's going to be 90% outline. What i already have is a very simple artist's acrylic. No, I don't have airbrush equipment but I will pick up a basic kit. Just happy to have steady hands ^.^

Gordon Bellerose wrote:A poly finish is one of the toughest to work with.
They are very hard, and will be difficult to sand to a point that you have a paintable surface.
I don't know your paint / art process, so I cannot comment on that.

To re-finish the poly afterward is not going to be easy, depending on what kind of poly it is.
Most commercial poly finishes are cured with a high power UV light.

The UV curing will be the only loose end... what happens to a poly that air-dries?

You've all been great, wish me luck! I'll post the end result for reference:)

Polyurethanes are not UV curing though some of them are 2 or 3 part catalyzed aka 2K & 3K finishes, (basically the same stuff used as a top-coat in automotive finishes). Still nasty stuff you would have to spray out doors with an organic chem filter mask and you'll only have 20-30 minutes or so to spray and then get the airbrush cleaned out before it starts to set up. This is where the waterborne polyurethanes come in as they are low tox and easy to clean up. Also you can buy them anywhere. They won't be quite as hard or clear as the solvent based versions but much cheaper and plenty adequate for a guitar.

David King wrote:Polyurethanes are not UV curing though some of them are 2 or 3 part catalyzed aka 2K & 3K finishes, (basically the same stuff used as a top-coat in automotive finishes). Still nasty stuff you would have to spray out doors with an organic chem filter mask and you'll only have 20-30 minutes or so to spray and then get the airbrush cleaned out before it starts to set up. This is where the waterborne polyurethanes come in as they are low tox and easy to clean up. Also you can buy them anywhere. They won't be quite as hard or clear as the solvent based versions but much cheaper and plenty adequate for a guitar.

I love that you brought up automotive types because a friend who was a talented mechanic for about a decade was describing today how he dealt with dry times and such, compared to how he treats his guitar these days. Crazy.
Yes, I'll have a clear plan once i just get hands on this one and feel around. Thanks!

i'll bet that shellac would stick to sanded polyurethane.
actually i think i tried french polish over endurovar (which is polyurethane) and it seems great.
and because this is the top of the guitar, i think it would be rugged enough.

Hannah, do you know how to French Polish? if not, it may be a bit late to learn considering your deadline.
google "french polish" and you will find some pretty good tutorials on youtube.
shellac does spray very well tho, so if you get an airbrush, you may be able to use that. it is difficult to get a good "whole top" finish with an airbrush.

wait for it...

Chuck Tweedy wrote:i'll bet that shellac would stick to sanded polyurethane.
actually i think i tried french polish over endurovar (which is polyurethane) and it seems great.
and because this is the top of the guitar, i think it would be rugged enough.

Hannah, do you know how to French Polish? if not, it may be a bit late to learn considering your deadline.
google "french polish" and you will find some pretty good tutorials on youtube.
shellac does spray very well tho, so if you get an airbrush, you may be able to use that. it is difficult to get a good "whole top" finish with an airbrush.

wait for it...

Hey, not a bad idea. Customer decided to tell me LAST NIGHT he's fine with a pick-up and drop-off so i have more than one day. He has not yet chosen a pick up date for me to even begin so im not rushing so hard after all>_>
I will study up on that and see what's up. Thanks!!:) I'd love to dig into these techniques after the current project, period.

The objective of sanding is to obtain a state of 'high surface energy'. When you remove material from the surface you're breaking chemical bonds, and it takes a while for the resulting 'loose ends' to find things in the air or the surface to latch onto. If you put on paint or glue during that time it bonds well. Note that this is a chemical process; you're not looking for 'tooth'; a rough surface in a mechanical sense. During WW II the Forest Product Lab did work on this and found that gluing within 15 minutes of working a surface gave a measurably stronger bond, and that planed surfaces worked better than sanded ones.

The standard test for surface energy is to spritz the surface with a mist of water. Water is a polar molecule; there is a bit of a static charge across the molecule, if you will. When the surface energy is high the charged ends of the water molecules are attracted to those open bond sites, and the water spreads out into a film. If the surface energy is low it beads up in droplets. The angle between the drop and the surface is a measure of the surface energy. I just saw a paper (in 'Science', iirc) on the problems of getting an exact measurement of that angle: it sounds 'New Age' but it's not.

I have seen products, with names like 'Sand Ban', that are purported to achieve that sort of result chemically. You could try something like that on a small spot to see what happens. You can also use a very fine abrasive, after thorough chemical cleaning to get off all of the pepperoni grease, which would minimize the amount of finish that had to be removed. Re-coat times are predicated, as near a I can tell, on allowing chemically cured finishes such as traditional varnishes and polyurethane, to mostly cure, but still have some 'loose ends' for the new coat to bond to. In brushing varnish I notice a certain 'drag' of the brush when the surface energy is high, and you get the same thing in French polishing when the surface is building fast.

So; see if you can find a chemical treatment that will do the trick without sanding. If not go with the finest abrasive you can get away with and dull the entire surface. I have found that wet sanding tends to interfere with the bond between coats of varnish: I suspect that stuff dissolved in the water is reducing the surface energy. Sand dry. Then I'd apply a very thin clear coat almost immediately, before the energy drops. If the clear coat is solvent based this should give you enough time to apply your art work. Seal it in with one or two clear coats.

Hello, makers!
FINALLY finished this damn project.
Here is a poorly lit shot of the after-poly, due to the storm which sprang up immediately following sealing and staging this thing to dry on my apartment balcony…>.<
Removed strings
Detail cleaned
No loose finish from original build, so didn’t sand first
Handpainted over the course of the past 2 days straight. Literally about 16 hours.
Was lucky the original finish was a gloss because that allowed me to simply wipe back acrylic details that weren’t to taste…customer was questioning through ALL the progress shots yesterday ssooo never doing that again, and tadah!
Lined with FrogTape and shop towels
Set outside and poured clear coat Satin finish polyurethane by Minwax (NOT my favorite, but was attainable with this deadline>.>)
Seems to be setting up smoothly, was able to foam brush the finish with minimal bubble drama
Now this damn thing is showing a shadow over the whole streak where the player had been wearing down into the wood where a pick guard would usually be. I worried he’ll freak out but this smudge is where I was attempting to remove pencil and paint, but it smeared to far into the chipped area, and it seemed very nearly normal color until the finish settled in an hour after pouring.

Am I screwed? He loved the picture, but now it’s darker there. Wish me luck…

Hannah

Sorry, trying to attach images, this should do it!
~H

Wow!

Wow - to add to Bob's/
Excellent art - many of us are jealous of your ability to lay that down in 2 days. Looks great!

Your "bad spot" needed to be sealed before you did the whole overcoat. Is it rough? Did the Minwax finish raise the grain of the spruce? The color does not look too bad, but the texture looks rough.
If the wood is damaged there from pick wear, and it still looks "pick-worn" then i would just leave it. If the grain is rough due to raised grain, I would sand very lightly to remove the fibers. Then it is your call if it needs to be recoated - or left.
He should not freak out - that is a pick-worn spot - damaged spruce is generally left alone because there's not much you, or anyone, can do to repair it.

Chuck Tweedy wrote:Wow - to add to Bob's/
Excellent art - many of us are jealous of your ability to lay that down in 2 days. Looks great!

Your "bad spot" needed to be sealed before you did the whole overcoat. Is it rough? Did the Minwax finish raise the grain of the spruce? The color does not look too bad, but the texture looks rough.
If the wood is damaged there from pick wear, and it still looks "pick-worn" then I would just leave it. If the grain is rough due to raised grain, I would sand very lightly to remove the fibers. Then it is your call if it needs to be recoated - or left.
He should not freak out - that is a pick-worn spot - damaged spruce is generally left alone because there's not much you, or anyone, can do to repair it.

Thank you!!
This spot may not be reparable physically, but I wish I'd gotten the damn darkness out before it saturated. Ugh. Yes, maybe sanding back in tomorrow evening would pick up the dark fibers and I could touch it up with clear. He knows it's beaten up but I hope he's not bothered by the new shadow. Just looks dirty that's all. If I mess with it won't the finish create edging issues or just sink in nicely? Turns out I grabbed an oil base after all, probably fine to manipulate.

Regarding the paint timeline, the DRAFT alone took 9 hours to tweak and a sharpie for Jon to review and approve the final design. The painting was awkward; not realizing the acrylic viscosity was wrong without keeping it slightly watered down to make it glide across the damn preexisting gloss made for many ugly edges, BUT the lack of "tooth" allowed for easy wipe removal of screw-ups with a damp cloth.

This you see now ended up being collectively redone about 7 times. I think. Probably more.

Anyhoo...Now that I have a thorough understanding of what type of brush to provide proper line control, what viscosity to go for, and wise prep procedure, I feel ready for just about anything^_^

I'm based in North Carolina and have reserved my off days, Friday and Saturday, for such commission work. I've always found myself digging into the local music community from singing at open mics to sharing lyrics with my dear friends who play far better than I.

You've all been wonderful help!
Goodnight!

Pre-pour clear daylight shots^_^

The guitar has a top crack in the lower bout (between the eagle and the feather) that should have been taken care of before you painted. But that is water under the bridge now.
the pick worn spot will just get beat up again, but you put some finish there to slow down the future damage.

A water-based finish will darken the raw section of grain by the sound hole when wet but should lighten up as it cures.
I think it looks great all around.