Finishing-Nitro-Wiping question

[PhilQ]

A question for the nitro/finishing people:

I am shooting nitro for the first time (I usually french polish my guitars). I am trying to dial in the right viscosity and shooting pattern with the gun to avoid runs. Not easy!

I have a question: I am getting white specks of dust, which I think are lacquer residues from the sanding between coats. I've just been wiping the guitar with a damp cloth, letting it dry thoroughly, and shooting again. But it doesn't seem to get rid of all the dust.

What do you/can you use as a "cleaner" to wipe the guitar before shooting again, and which won't leave problematic residues when shooting the nitro?

Thanks!!

[GolfSteve]

After sanding I usually wipe the guitar with a dry paper tower (the blue shop towels) and blow the guitar off with compressed air. Any residual lacquer dust is redisssolved when I shoot the next coat.

Occasioanally I'll wipe the guitar down with mineral spirits. I worry that this might introduce contamination, but it doesn't seem to have caused a problem yet.

My largest contamination issue seems to be due to hand lotion. Perhaps I apply lotion then head out to the shop an hour later and leave a thumb print on the headstock. A week later I shoot laquer and #($*&#.

[charles Tauber]

Standard finishing "tack" cloths work fine.

[PhilQ]

Originally Posted by charles Tauber

Standard finishing "tack" cloths work fine.

Yeah, they do. But I'm trying to minimize waste as much as I can. Thanks for the suggestions.

[charles Tauber]

Originally Posted by PhilQ

Yeah, they do. But I'm trying to minimize waste as much as I can. Thanks for the suggestions.

A laudable undertaking. One tack rag lasts me for years, when used in conjunction with a damp rag and compressed air to first remove most of the particles.

[PhilQ]

Originally Posted by charles Tauber

A laudable undertaking. One tack rag lasts me for years, when used in conjunction with a damp rag and compressed air to first remove most of the particles.

My bad, I thought they were single use. Do you store it in a zipper bag to keep it from drying out?

[charles Tauber]

Originally Posted by PhilQ

My bad, I thought they were single use. Do you store it in a zipper bag to keep it from drying out?

You can, if you'd like. I find that they don't dry out: they are coated with a waxy substance that doesn't dissipate. You can also make your own, if you feel so inclined. I buy them for a few bucks.

[PhilQ]

Originally Posted by charles Tauber

You can, if you'd like. I find that they don't dry out: they are coated with a waxy substance that doesn't dissipate. You can also make your own, if you feel so inclined. I buy them for a few bucks.

Great. Thank you. No chance of contamination with said substance?

[charles Tauber]

Originally Posted by PhilQ

Great. Thank you. No chance of contamination with said substance?

There is, yes. Don't "scrub" the surface with the tack rack, just a light wipe.

I don't use them with water-based finishes, but that isn't what you are asking about.

[mirwa]

Originally Posted by PhilQ

I am getting white specks of dust, which I think are lacquer residues from the sanding between coats.

Large sections of white specks of dust when spraying nitro usually indicates you need to add some more thinners, the mix is a bit dry and the overspray gives a white dusted appearance.

If its actually dust, then you need to clean the area a bit further before spraying

We have a spray booth, heres out prep process, cleanliness is so important

- we sweep the floor up and collect it in a pan and put it in the bin,
- we mix out paints and put the paint in the guns put them into the guns inside the booth
- hang the guitars in the booth
- wax and grease clean the guitars
- turn the extraction fans on and close the doors
- we then use a spray mop and quickly mop the floor with the fans on and door closed
- air blow down the guitars to ensure no dust on the surface
- do a test spray with the guns on the wall (paper taped to walls)
- spray guitars


Steve

[charles Tauber]

Originally Posted by PhilQ

I am getting white specks of dust, which I think are lacquer residues from the sanding between coats.

Originally Posted by mirwa

Large sections of white specks of dust when spraying nitro usually indicates you need to add some more thinners, the mix is a bit dry and the overspray gives a white dusted appearance.

If its actually dust, then you need to clean the area a bit further before spraying

Steve

Sprayed finishes require a controlled environment and meticulous process in order to get flawless results.

There are numerous aspects of the environment and process that can conspire against a perfect finish. Dust specs from sanding between coats is one of them. As Steve points out, overspray is another. Yet another is lack of cleanliness (finish build-up) at the gun nozzles.

A top-quality sprayed finish is difficult to achieve for the one-off builder/beginner. To obtain the best finish, it is important to identify the cause of the imperfections one is experiencing.

[mirwa]

Yes, well articulated,

My point was even in the most clinical of enviroments that we try to create, dust still happens.

For someone at home trying to replicate what we do in a shop, you really need to be less hard on yourself for small imperfections.

Steve

[mirwa]

Heres my Nitro spraying process, I try to do my big paint jobs on the weekends rather than during the week, just came out of the booth today doing 3 guitars.

Raw wood sand with 220 grit sandpaper dry
Prep the wood with whatever washcoat and sealer you want to use, allow to dry and level out with 350grit dry.

My first two spray coats are build coats, that is I want volume, do not really care about gloss of the gun, so I use a 1.8mm tip gravity fed gun, nitro 80/20 thinners, I will lay a mist just to create tacky surface and follow up with a full coat.

Allow to dry until minimum 4-6hrs later

I do not sand, I use a razor blade and scrape any imperfections / dust residue / runs of the initial first coat

Second coat 1.8mm tip gravity fed gun, nitro 70/30 Thinners, tack coat and then full coat

I allow the guitar to hang for about 3 days

Razor blade any major imperfections of, lightly sand the surface with around 600 sandpaper - wet and detergent

Clear gloss coat - I change my gun to a 1.4 tip gravity fed and do a nitro 60/40 thinner coat, I am looking for gloss of the gun so Ill play with my spray gun setup pressures and air feed fluid feed to achieve

Ill apply another 2 coats and sometimes I may even thin it out further to 50/50

Thats it let it dry, I leave it alone for a week, then buff time......

Sometimes you may need to sand just before final buffing, but it comes down to what finish you are after.

Thats for nitro.

For painting in acrylics / waterbases / 2 pack poly urethanes / enamels / Ultraviolets / Metalics and so forth, I have a different process for everyone of them, no two are the same.

This is what works for me, does not mean it is an industry accepted method

Steve

[Howard Klepper]

Originally Posted by PhilQ

A question for the nitro/finishing people:

I am shooting nitro for the first time (I usually french polish my guitars). I am trying to dial in the right viscosity and shooting pattern with the gun to avoid runs. Not easy!

I have a question: I am getting white specks of dust, which I think are lacquer residues from the sanding between coats. I've just been wiping the guitar with a damp cloth, letting it dry thoroughly, and shooting again. But it doesn't seem to get rid of all the dust.

What do you/can you use as a "cleaner" to wipe the guitar before shooting again, and which won't leave problematic residues when shooting the nitro?

Thanks!!

Why are you sanding between coats? There is no need for it with nitro lacquer, if the purpose is adhesion. The lacquer will melt into the coat before. Sand between coats only for the purpose of leveling. I only do that once in the course of a finish--between the body coats and the topcoat(s).

Superficial amounts of sanding dust will melt into the next coat, after you have cleared most of the dust with blowing air or with a tack cloth (BTW, raw linseed oil is usually the tacky stuff). If you have a deep pore the sanding dust may not be easy to clean out and may not melt. In that case, you didn't fill the pores well and you have a problem.

Last, the white stiff that looks like fine threads is nitro "cotton blush." A small amount of it will either wipe off or melt in the next coat. If you are getting a lot of it, it is likely either because you are spraying in too hot an ambient temperature, or using cheap thinner. You can fix that with a retarder, but that will slow the curing of the lacquer. Better to upgrade your thinner. Do not thin with the hardware store stuff. Use that for cleanup. Thin with the proprietary thinner made by a good lacquer manufacturer.

[John Arnold]

Sand between coats only for the purpose of leveling.

For leveling, I prefer a thin scraper rather than sanding. When I have level sanded, I used 220 grit stearated paper (dry).
Like Howard, I do the leveling one time. I spray nitro over two days (4-5 thin coats a day), and level the lacquer on the porous hardwood at the beginning of the second day. No between-coat leveling is necessary on the spruce, which only gets 4 or 5 coats.

Superficial amounts of sanding dust will melt into the next coat

That is the beauty of using lacquer.

I use a fan to speed up the curing time. Lacquer drying is strictly a function of evaporation.

After the lacquer has cured for a few days in front of the fan, I wet sand and buff.