How to poly over complicated dye patterns?

[phatstats]

Hey everybody, I put a lot of time into learning how to dye wood (my first attempt to finish wood ever!) And I think I got a pretty cool result. I have the guitar grain filled and dyed up, but now I'm wondering what a procedure looks like to get this thing a polyester or urethane resin clear gloss without disturbing the dye. Ive seen a million and one procedures for polyurethane, but I'd like to go the polyester or urethane resin route simply because this is going to be my beater/gigging guitar since my present gigging guitar has appreciated to the point where I don't really feel comfortable taking it out with me and as I understand it, polyester is near bulletproof as long as you don't drop it (Im unconcerned with the suspected slight drop in acoustic resonance that is reported but unproven since this is obviously a higher gain electric anyways). I have the following questions:

1) I am terrified of polyurethaning over shellac myself due to witness lines, but I am confident this procedure would not disturb the dye itself because I have shellac'd over dye with an LVLP gun successfully on scraps so far, and as I understand it, from there the dye would be locked in and no issues would persist btwn dye itself and the polyurethane. If applied with an LVLP gun, are witness lines really as prominent/easy to get as the internet makes it seem? Ive seen some seriously ugly looking errors out there... if it's something I'll be able to avoid if I try it 3 or 4 times on scraps? Great. 10 or 20 scraps? I've got time 40, 50+ times? Maybe not... how easy is polyurethane to work with and get a mirror out of?
2) are there procedures for polyestering yourself with some sort of intermediate layer that wont disturb dye? Ive contacted Solarez about their polyester resin over shellac as an intermediate, but they have no clue, and I'd rather at least have some information that what I'm attempting will work before grabbing a gallon of the stuff and testing on scraps.

 

[Cowbell Fever!]

As far as I know poly is a ok over shellac. HOWEVER I would test to be sure, like on a scrap . If you aren't gonna spray, why not use wipe on poly?
I am sure Sadie will chime in soon as she knows virtually everything about finishing clears.

 

[phatstats]

As far as I know poly is a ok over shellac. HOWEVER I would test to be sure, like on a scrap . If you aren't gonna spray, why not use wipe on poly?
I am sure Sadie will chime in soon as she knows virtually everything about finishing clears.

Agree water based polyurethane is generally okay. The problem is polyesters and urethanes seems less certain, and in 2k automotives, a slight error -> finish never hardens. I am not wiping anything on directly over dye; all test pieces ive tried wiping the aniline dye lifts slightly which is unacceptable to me. The base coat will necessarily be LVLPd by me or a pro; too delicate. Or do you mean LVLPing shellac and then wiping on poly? Isn't that what causes witness lines when seeking a mirror finish? I now know a good bit about dying, but still nothing about glossing, so I am here to learn and could be mistaken

 

[Cowbell Fever!]

I was referencing oil based poly over shellac being fine. However, you have a lot of time in and dye you are using I don't know about. I thought you had sealed with one coat of shellac already.

In any case, test it or wait for more info !!

 

[teleme01]

i tried dying walnut yellow,  and then i tried wipe on poly and wiped off all the yellow dye, so obviously i am a bad source of what to do but am a valuable source of what not to do,  my suggestion if you want it is to apply a spray on ,  but a spray on what ?  laquer,  shelac,  sealer,  thats what i dont know

 

[Rick]

I've used the keda water based and min-wax oil based stains, with poly or true oil on top.  Never had a problem.
Got pictures?

 

[stratamania]

The only way you will know for certain and have confidence is to do some test pieces.

 

[phatstats]

The only way you will know for certain and have confidence is to do some test pieces.

I totally agree.. I just wanted to get some confidence if there were any known procedures for polyestering over dye that have been executed successfully before I drop down the cash and start practicing... if not I guess I'll just toss something at the wall

 

[phatstats]

i tried dying walnut yellow,  and then i tried wipe on poly and wiped off all the yellow dye, so obviously i am a bad source of what to do but am a valuable source of what not to do,  my suggestion if you want it is to apply a spray on ,  but a spray on what ?  laquer,  shelac,  sealer,  thats what i dont know

Yup that's what Im very afraid of.. haha. I agree spray on something... but what goes under polyester/urethane and does not disturb dye, or will reliably not put witness lines in polyurethane, seems real not clear

 

[phatstats]

I was referencing oil based poly over shellac being fine. However, you have a lot of time in and dye you are using I don't know about. I thought you had sealed with one coat of shellac already.

In any case, test it or wait for more info !!

Nope I haven't done anything yet... hoping for either a report of something that works under a polyester before sinking in the cash... I honestly didn't expect the dye to turn out well enough that I'd actually be all that concerned about getting an exact mirror finish hahaha

 

[Sadie-f]

OP, that's a fantastically beautiful body you've got going there congratulations!

First, I agree heartily with teleme01 about caution in wiping. For my current project, I used stewmac black dye, which I diluted in ethanol. It definitely mobilized some when I put oil over, and as oil must be wiped off, I went with blotting first. That used far more paper towels than I'd have liked, and also got the job done.

For this project, I'm also starting out in the critical first layers with spraying the tung oil, which I'd usually wipe on. It's too many colors, and while bleed across rainbow sections is good, I'm doing that carefully.

Once I have the colors finished, they'll be locked in with the polymerized tung oil, and I can go back to more normal methods.

Anyway back to what you're trying to do. If you have a good spray rig, then I'd say just spray polyurethane direct onto the dyed wood, maybe starting in thin layers.

If you're not blessed with fancy equipment, then I'd agree with Jack that a first layer of shellac is your best first defense and a way to isolate the dyes from following layers. That said, while  shellac is considered to be a universal base for all things to follow, I don't know that that universal applies to urethane's and polyesters, so I think you need to do research on that specifically.  Also you need to get a wax-free shellac, that's really important if you go that way.

I've sprayed isocyanate cured urethanes as well as water-based urethanes and once you have a base that's all really easy, again, provided you have a spray rig.

Testing, testing

 

[NedRyerson]

Shellac is an amazing substance.  Off-topic, but I'm doing a fabric-topped body right now, and so far, shellac has been the only thing to effectively protect the fibers of the fabric and mitigating color bleed before I top-coat it with something more protective. I've tried both poly and epoxy, and I'm leaning toward the epoxy.

 

[teleme01]

yes,  so i think the recomendation is rattle can shellac,  but the question is should you first spray it with sealer ?

 

[Rick]

What dye did you use?

 

[phatstats]

What dye did you use?

It's all keda in a 3 layer sandback. When I realized it was gonna turn out badass after layer 1 dried, I started taking videos which have all my dye recipes/concentrations recorded as well which I'll post when I get it glossed up!

 

[stratamania]

Perhaps using a 2K Poly spray might give you the durability being sought but make the job straightforward. I would still advise a test run just to be certain and for confidence purposes.