Repel spots in water based lacquer?

[Kaisergrendel]

Hi all, I'm building a set of speakers with some Colortone WB lacquer from Stewmac. Before I actually touch the speakers I'm doing some sample boards. Having some weird problems with my 3rd one. I've asked a luthier's forum where I learned most of these finishing tips from but so far nobody's come up with an answer.

I sprayed my first neat coat of WB lacquer today on my 3rd sample board. Like the washcoats before, I'm getting small circular spots between 2-5mm in diameter in the coat where the lacquer has dried incredibly fast (or has shifted off the region.) while the rest of the coat is still wet.

After letting the first day's coats dry on my 3rd sample board the fast-drying spots have now become dimples in the finish. There's no particular pattern to the way the spots appear, they're just generally scattered across the surface. Here's what I did to the board previously:

1. Filled with turps-based grain filler. Sanded with stearate free paper.
2. Filled with Timbermate (water based filler). Sanded with stearate free paper.
3. Stained with spirit-based dye.
4. Lightly scuffed with synthetic abrasive pad.
5. Mixed WB lacquer with spirit-based dye, toned edges.
6. Sprayed 3 medium thickness coats of WB lacquer.

I have a feeling these are "repel spots," but I can't find much documentation about it. They're definitely not fisheyes as they're still in contact with the veneer, which in my mind rules out the turpentine in the grain filler rejecting the WB lacquer. Can anyone tell me what this is?

[tea lady]

Water based laquor with spirit based dye? I wouldn't think they would mix. More like emulsify for a bit like salad dressing before separating again. Wouldn't you need to use water based dye? The spots are prolly spots of spirit dye that then wont take water based on top! That's what I reckon anyway.

[Kaisergrendel]

Water based laquor with spirit based dye? I wouldn't think they would mix. More like emulsify for a bit like salad dressing before separating again. Wouldn't you need to use water based dye? The spots are prolly spots of spirit dye that then wont take water based on top! That's what I reckon anyway.

At first I thought that might be the case, but during toning the lacquer and dye were mixed together and quickly shot out atomized through a spray gun at a *very* low material setting, close to letting out no material at all. The droplets immediately flashed off on the veneer, so there was little chance of the emulsion breaking apart. The mixture was sprayed the heaviest on the edges of the board and almost never in the middle but there isn't an over-representation of the spots anywhere on the board - the pattern is random and regular. In addition, I rubbed in quite a heavy coat of spirit dye as the base color before the toning even started.

Now that I've tried to I remember the repel spots first appearing during the washcoats stages, before any of the dye even reached the board. I just didn't take note as they disappeared once the washcoats dried, probably because the coat was so thin. At this point it could either be contamination from the veneer backing glue, oil contamination from the spray gun, or the turps-based grain filler. Fairly sure I can eliminate timbermate as a problem.

[tea lady]

or the turps-based grain filler. Fairly sure I can eliminate timbermate as a problem.

Could be. Maybe you could try a water based grain filler? Or a shellac grain filler? (Which is mello based . )

Why do you want to use water based laquor? Fume probs? I can't stand the smell either. But it dries really quickly, and part of how it works is that the next coat partially dissolves the last so it keys is. I would guess the water based one would not do that. It would just be another layer. So any "resist spots" never get smoothed over no matter what you do.

[The Bleeder]

You say the "patern is random and regular"....... I'd be leaning to an oil/(may even be water) contamination.

What has the compressor hose be used for..... Check your water traps .. try a new hose....

Eliminate the compressor and it fitting first.

[Kaisergrendel]

Could be. Maybe you could try a water based grain filler? Or a shellac grain filler? (Which is mello based . )

Why do you want to use water based laquor? Fume probs? I can't stand the smell either. But it dries really quickly, and part of how it works is that the next coat partially dissolves the last so it keys is. I would guess the water based one would not do that. It would just be another layer. So any "resist spots" never get smoothed over no matter what you do.

Timbermate is water based. I just whip it up with water and it's ready to be used to fill grain. I used a different grain filler *before* applying timbermate called Wattyl Grain Filler. It was a nasty thick goop that was a nightmare to sand off. It didn't even fill most of the holes, hence why I went back to Timbermate.

Mostly because my current spray booth would probably explode if I used nitro. I don't have the money or means to construct an explosion proof booth. I was looking around in Melbourne for nitro for months, and when I finally found it, I realized it just wasn't going to be safe enough for me to use.

I picked the WB lacquer I'm using because it's designed to mimic nitro in terms of workability. STEWMAC.COM : ColorTone Waterbase Lacquer

It burns in, dries fast, and cures hard enough to buff to a mirror finish.

You say the "patern is random and regular"....... I'd be leaning to an oil/(may even be water) contamination.

What has the compressor hose be used for..... Check your water traps .. try a new hose....

Eliminate the compressor and it fitting first.

The entire compressor setup including the hose is relatively brand new and only has ever been used for either straight air gunning (cleaning) or spraying WB lacquer. There were no repel problems with my first two boards.

There's a filter at the mouth of the compressor, and another one attached directly to the gun itself. The one at the compressor works so well that the one under the gun never gets a single drop of condensation.

I'm going out to spray another few coats and see if the repel spots multiply (pointing towards a problem in the compressor rather than something that's on the board.) Will report back.

[Kaisergrendel]

Update: Sprayed 3 coats today. For the first 2 coats I thought I had it under control but the craters came back more and more with each coat. I submerge the spray gun nozzle in DA(metho) between coats to keep it wet. My suspicions are now focused on this.

The thing is before this I always primed the gun with metho before spraying the WB lacquer. It simply could be a case of high concentrations of unsprayed metho being left behind in the chamber and the nozzle.

[tea lady]

Pokig around on that site, they have this stuff called "fish eye flow out". Caused by silicon or other contamination. Unfortunately that don't ship it outside the US! But I guess this sort of this is a common problem. It might give you a different term to google.



STEWMAC.COM : Details about Fisheye Flowout

[tea lady]

Update: Sprayed 3 coats today. For the first 2 coats I thought I had it under control but the craters came back more and more with each coat. I submerge the spray gun nozzle in DA(metho) between coats to keep it wet. My suspicions are now focused on this.

The thing is before this I always primed the gun with metho before spraying the WB lacquer. It simply could be a case of high concentrations of unsprayed metho being left behind in the chamber and the nozzle.

Is that what they recommend? After a quick read I have a vague memory of them saying something about 50/50 mix of metho and water. What about emailing the company?

[ian]

Timbermate is water based. I just whip it up with water and it's ready to be used to fill grain. I used a different grain filler *before* applying timbermate called Wattyl Grain Filler. It was a nasty thick goop that was a nightmare to sand off. It didn't even fill most of the holes, hence why I went back to Timbermate.

Mostly because my current spray booth would probably explode if I used nitro. I don't have the money or means to construct an explosion proof booth. I was looking around in Melbourne for nitro for months, and when I finally found it, I realized it just wasn't going to be safe enough for me to use.

I picked the WB lacquer I'm using because it's designed to mimic nitro in terms of workability. STEWMAC.COM : ColorTone Waterbase Lacquer

It burns in, dries fast, and cures hard enough to buff to a mirror finish.

The entire compressor setup including the hose is relatively brand new and only has ever been used for either straight air gunning (cleaning) or spraying WB lacquer. There were no repel problems with my first two boards.

There's a filter at the mouth of the compressor, and another one attached directly to the gun itself. The one at the compressor works so well that the one under the gun never gets a single drop of condensation.

I'm going out to spray another few coats and see if the repel spots multiply (pointing towards a problem in the compressor rather than something that's on the board.) Will report back.

can you expand a bit on why you're using a grain filler?

I've successfully used the "thick goopy" Wattyl Grain Filler.
It's not intended for filling nail and screw holes.
It's a "true" grain filler that you're supposed to wipe on, let partially dry and then scrap the excess filler off the surface using a squeegee and/or coarse hessian and working across the grain. When dry it forms the base for a subsequent mirror finish. Other formulations of this sort of grain filler use talc and shellac.

BUT, if you have the gear to spray lacquer, you can use the lacquer as the grain filler
spray two coats, scuff sand, then spray two more, repeat till you can no longer see the pores — then start on your top coats.


your spot problem sounds like it's probably oil and water from the compressor — do you have a water / oil filter immediately before the line going to the gun?

[KJ401]

It sounds like silicone contamination. It could be from the turps based grain filler, could have been on the wood, might have been something on a rag you may have used at some stage to dust or wipe the timber; might even be something in the metho that shouldn't be there. If you own a diesel vehicle, it could even be particulants from the exhaust.

Using fish eye remover may well stop it happening again - and it is readily available here - try an autopaint supplier. BUT you have to deal with the craters, the spots of contamination you have. Fish eye remover will reduce the surface tension of the WB finish when its wet so it will flow out and over the silicone contamination, not around it as it is doing at the moment. If you want a flat finish, you'll have to cut back removing the craters.

Unfortunately you may have a couple of problems - you may spread the contamination as you sand. You may also find you cut through the coats of the WB finish, and end up with quite visible tidemarks.

To reduce the chance of spreading the contamination, wipe every face down with Prepsol ( or unleaded petrol). Then sand. Blow the dust off, and wipe everything down again with MEK (methyl ether ketone) - paintshops should have this. Read the ingredient label carefully to make sure it is only MEK.

Then respray - having added your fish eye remover to your finish. But before you use Fish Eye remover, make sure it is OK to use it in the WB finish you are using. It can cause far worse problems than the one you are trying to solve. Be very very sure you put a good dose of MEK through your gun after using any finish with Fish Eye remover in it.

And nitro is not so volatile that I wouldn't use it without an explosion proof booth. If you've got exposed fan motors in a confined space I might worry but it's the dry overspray dust that is actually the issue - and it can be for any solvent based finish if the overspray dust is allowed to collect and is ignited somehow. WB finishes are a lot fussier as are 2 pack - you may not be able to work out where the contamination is coming from. It may never happen again. You may not be able to sort it out. If that happens, reconsider nitro or precat.

And as for ending up with tidemarks when sanding back through the coats with WB finishes? No easy answer there, though the use of piratical and colourful language vaguely helps.

[KJ401]

Sorry - forgot to address the compressor / gun issue. Don't assume your filter is trapping everything you want it to trap - if it's a water filter, it wont necessarily be doing the job you expect with oil. Filters aint filters. The filter that came with your compressor may deliberately allow oil through the lines - it's how air tools are lubricated.

Check what type of filter you actually have - check the cartridge inside it. I'd visit the autopaint shop and buy a reasonable quality water AND oil filter and add it to my air line about half way between the compressor and the gun. Also helps if you loop your airline up from the compressor, then get it to dip - put the new filter on that dip - and then loop it back up to your gun.

If you have got oil in your lines - replace them before you put the new filter in place. Also wash your gun out with MEK a few times, strip it apart and soak everything in MEK overnight. Be careful though with any nylon or neopryene washers - they can dissolve.

[Kaisergrendel]

Pokig around on that site, they have this stuff called "fish eye flow out". Caused by silicon or other contamination. Unfortunately that don't ship it outside the US! But I guess this sort of this is a common problem. It might give you a different term to google.



STEWMAC.COM : Details about Fisheye Flowout

I can think of a locally available flow assisting additive called Floetrol, which could yield similar results. Might try that if I keep having this problem.

can you expand a bit on why you're using a grain filler?

I've successfully used the "thick goopy" Wattyl Grain Filler.
It's not intended for filling nail and screw holes.
It's a "true" grain filler that you're supposed to wipe on, let partially dry and then scrap the excess filler off the surface using a squeegee and/or coarse hessian and working across the grain. When dry it forms the base for a subsequent mirror finish. Other formulations of this sort of grain filler use talc and shellac.

BUT, if you have the gear to spray lacquer, you can use the lacquer as the grain filler
spray two coats, scuff sand, then spray two more, repeat till you can no longer see the pores — then start on your top coats.


your spot problem sounds like it's probably oil and water from the compressor — do you have a water / oil filter immediately before the line going to the gun?

Yeah, I made the mistake of leaving too much on the surface. When I tried to sand it it quickly gummed up on my discs, ruining them. I don't intend to continue using it as it's just really asking for trouble mixing it with WB lacquer.

I might try using the lacquer as a filler. The only problem is it's pretty wasteful to do it, and it costs dearly to ship more of it from the US. At the moment I'm actually quite happy with Timbermate, which is water based to boot.

There's a filter at the compressor and another filter immediately before the gun. The one near the compressor does all the work - the one near the gun is always bone dry.

Is that what they recommend? After a quick read I have a vague memory of them saying something about 50/50 mix of metho and water. What about emailing the company?

I think I remember reading somewhere to prime with metho first, then water. Can you remember where you saw this tip?

I've fired off an email to Stewmac, will see what they say.

(Not quoting as this post is long enough) KJ401: That's quite a bit to absorb! The first thing I'll try is flushing the gun with water after priming with metho. The worst case of cratering I got was after I made the mistake of spraying even when the nozzile was dripping metho. I somewhat recreated this by brushing the WB lacquer onto some scrap wood, then dripping some metho on it - it definitely repels the lacquer, but eventually dissolves into it and the coat almost flows out evenly after. My hope is that this is what happens albeit with a slightly different behaviour when I spray with a nozzle wet with metho.

As I mentioned earlier in this post, I might try a flow assist additive in place of a true fish eye eliminator as it is virtually impossible to source it in Melbourne.

I probably won't find prepsol, but possibly an equivalent. If I do fall back to unleaded petrol, how can I be sure the additives in the fuel don't cause even more problems?

My booth is about 4x4', reasonably confined, and my fan is just a domestic box fan forced into spray booth service. Add to that the fact that I use a 300W halogen inside the booth for illumination, and I don't think anyone in their right mind would attempt to spray anything combustible inside.

The filters are called "moisture filters" and didn't come with the compressor. The one I attacked to the compressor doubles as a regulator and collects a yellowish, watery+greasy liquid. This is why I think it's doing its job as far as filtering water and oil is concerned.

Addendum: I think I forgot to clarify one very important thing. These "craters" or "repel spots" aren't places where the lacquer doesn't adhere to at all - rather the lacquer THINS OUT and coats the crater thinly while the majority of the lacquer pools around the craters. The lacquer DOES flow over these spots, just at the regular thickness.

[tea lady]

You haven't got any pics? No one with a macro camera near by?

If you are worried about the booth, you are near enough to Knox Woodworkers who are setting up a spray Booth for spraying NC laquor at the moment. Maybe you could join there to use the facilities? (I am a member, but the rest of the members are OK!. )

[Kaisergrendel]

You haven't got any pics? No one with a macro camera near by?

If you are worried about the booth, you are near enough to Knox Woodworkers who are setting up a spray Booth for spraying NC laquor at the moment. Maybe you could join there to use the facilities? (I am a member, but the rest of the members are OK!. )

Now that you mentioned it, I wonder I didn't do take a picture!

Interesting, do you get to keep your work there between coats?