Fret “shadows” when spraying tinted nitro? Way to avoid?

[Jmfranc]

Have a couple nice maple necks that were just completed and now time to spray with nitro.

Doing another strat neck and want to avoid problems I’ve had in the past that’s mainly the tint nitro layer not being even on the fretboard. On either side of the frets I get either a “shadow” where the tint is lighter than the rest of the surface or it ends up heavier on one side. I’ve tried vertically flipping my neck after each coat and still had the issue. Any tips on how to get a even coat?

I use stewmac nitro that I tint using their amber dye. I’ve used cans, prival sprayers, and a paint gun w air compressor. I’ve used the lightest possible coats which took me at least 7 or 8 coats to get the color I want and it was still a very thin finish when it was done. I’ve considered wiping on the amber dye mixed with acetone so I could get it even and then just spray clear but it doesn’t have the right look.

And spraying with no frets on the neck worked well until I pressed the frets in and the nitro cracked (massive crack between tuner holes when pressing in the bushings). I think I’ve tried it all. I’ve painted over a hundred bodies but the necks are killing me.

 

[KokoTele]

Lower air pressure, thinner lacquer so it still atomizes well with lower pressure, and experiment with the fan pattern.

I think there are two issues: one is that the high pressure air from the gun gets too turbulent at that corner and can't push it's way in there. The air at the surface stagnates and pushes the high pressure air away. The other is that if the spray approaches the surface at an angle, the fret itself blocks the wind and the paint droplets sail downwind a little ways.

I think the last time I mixed up a batch of neck amber, I increased the amount of tint I put in the lacquer so it would deliver a similar amount of color with a thinner film thickness.

 

[eallen]

If you are spraying you tint coat heavy your shadow may actually be the result of the color pooling around the fret. Go with like passes and go straight with the pattern.

Eric

 

[Sea Devil]

I haven't actually done this, but my instinct would be to spray with the neck on a horizontal surface, shooting from both sides and never along its length before the back of the neck is sprayed. I would then probably use thinner to remove all the finish that had ended up on the back, "tapering" it a little along the fretboard edge, then flip the neck over and spray the other side. Only a tiny amount of easily removable overspray (bounce-back and/or drift) would ever hit the fretboard side, and blending the edges would be easy.

The "shadows" you talk about might be the result of finish pooling around the edges of the frets just because it's still wet (see below -- a question of surface tension), but would more likely result from shooting along the length of the neck or shooting it in a vertical or tilted position.

 

[stratisfied]

Use an airbrush on the fretboard. You can build the color up evenly with more control and avoid puddles.

 

[Boreas]

I don't see any way of avoiding what @Sea Devil illustrated above. This is typical of spraying over the frets, and isn't a problem with spraying clear. I actually TRY to get those fillets. So:

1. Spray without the frets. Chamfer the fret slots with a file before pressing in frets to avoid chipping.

2. If spraying with frets on, try spraying just a couple DARK coats with the fretboard flat and level. Use enough tint to get it to your desired color fast, then switch over to numerous coats of clear until you are happy with the thickness. This way any pooling/fillets will not be darker at the frets.

 

[stratisfied]

Fenders have always had the finish overlapping the frets on maple fretboards. It seals off the fret slot from moisture and hand smegma.

 

[Beebe]

I ran into this as well, using amber shellac.

The problem for me was too much wet tinted material on the surface. My guess was that some kind of surface tension was causing flow.

My solution was getting the color I wanted with fewer coats (heavier tint in your case), or waiting longer between light coats.

Once I got the color I wanted, I still needed to be careful to keep the clear coats of Platina Shellac from melting into the tinted layers below. If I sprayed the clear too heavy it would cause the tinted layers to flow.

So I'd suggest spraying almost dry thin coats of the tinted material, and the same for most of the clear coats. You can spray the last few clear coats a little heavier handed to get the final surface to flow as there should be a pretty thick coat of dried clear protecting the tinted layer.

...at least that's the mindset I approach it with.

Edit: Where I described the tinted layers "flowing" I mean "traveling"... Towards the frets, or in areas without frets it might travel away from the wet area, like a drip of solvent would carry the material away in a ring.

You only want localized flow, like one droplet flowing into it's neighbors on the surface but for the flow to stop there.

 

[Silverface]

Are you spraying with the neck on a flat surface? It sounds like that. If so, you are spraying at an angle to the surface, which causes all sorts of problems with mil thickness and can cause thicker buildup at one side, with resulting color float.

I always shoot surfaces suspended or held vertically, and carefully maintain an even path with each pass (you should be making VERY thin passes - generally 3 per coat - with flow/coalescence and coverage beginning to occur ataround the third coat.

You want to spray absolutely parallel to the surface; with the rounded portion of necks you have to spray even more thinly and build the thickness, color depth and obtain coalescence more slowly, rotating the neck bit by bit.

Air spray is very difficult to use on curved surfaces and on fretted boards; this is where an HVLP really has serious advantages, as you can dial down to 4-5 PSI material pressure, which the large air volume (not pressure!) provided by the turbine giving you very fine atomization. This provides far more control over thickness and also has a side benefit of added pigment dispersion - plus almost no overspray or "bounceback"

If you are having the material flow with a fairly even gloss with your first or second coat you applying it WAY too thickly, trapping volatiles in the film. This is especially true of certain Colortone lacquers. Check the MSDS and if you see "alkyd resin" it's definitely a "lacquer enal - lacuer lblended with oil-based paint resin. These have to be sprayed VERY thin - I suggest only two passes per coat and flow (coalescence") and coverage not starting until the 3rd or preferably 4th coat.

The wetting agents/flow agents (surfactants) in all coatings are evaporative materials that both disperse and collect pigment - and they love to pull pigment into corners. Because lacquers dry only by evaporation (there is no such thing as a "cure time" for lacquer), and "lacquer enamel" blends dry more slowly, the thicker the coat the more time for pigment to be sucked into corners - like fret edges.

A coat of properly applied conventional lacquer dries completely in 30-60 minutes; but lacquers like some Colortone and virtually all Deft lacquers are actually lacquer blended with alkyd (oil based) enamel (aka "lacquer enamels" - not to be confused with Mohawks "lacquer enamel", which is simply a trade name for one of their pigmented lacquer lines), and a single coat may require several hours to a day or more to dry.

If you apply thick coats with trapped volatiles, pigment WILL collect in the corners, and it CAN happen even with thin coats; I don't use any lacquer enamels as the problem can occur at places like edges of neck pockets as well - and even with thin coats because of the extended evaporation period.

Tinting yourself can also be an issue, as you need to continually agitate the material after mixing (and unless you have a paint shaker handy, you need to hand-blend/stir for a minimum of 30 minutes to obtain even dispersion. Don't use a powered mixer on lacquer unless its an (expensive!!) explosion-proof unit, as the sparks can ignite the fumes causing a flash fire (I've watched it happen jus-t after advising a paint not to do it and him telling me "oh, it's no problem - and burn all the hair on his arms).

So vertical, 90-degree spraying (no "golf swings") with pieces suspended or mounted and not laying flat; VERY thin coats; extended material agitation (before loading, even if the gun has an agitation-type cup) combined with as low a pressure as you can get (with a very small needle/air cap) with precisely calculated thinning using a stopwatch and #2 Zahn cup should get you decent results.

That's the other critical factor - PRECISE thinning, and having the proper needle and air cap for lacquer. If the thinning is not exactly right for the material and air pressures AND being timed using a Zahn cup There are usually issues on more than just the fretboard.

Air spray and proper thinning/spray pressure using lacquers takes either professional training, of hit-or-miss experience or a lot of luck - and it's exponentially harder using slower-dry products.

I used to teach classes in equipment usage, and die-hards that wanted to stick with air spray - and I'm talking professional painters - switched to HVLP only while kicking and screaming at first, but once they were trained in how to use it properly most never used conventional air spray again.

 

[Old Verle Miller]

What Sea Devil suggested - go horizontal, face up. Lots of light coats. Do the back and sides later in the vertical, keeping overspray away from the fretboard.

 

[KokoTele]

Lots of good information above, just not for the problem that jmfranc described

Think of tan lines next to the frets instead of dark spots. The finish can be tricky to lay down right next to the fret.