Questions for users of Behlen Stringed Instrument Lacquer

[charles Tauber]

Originally Posted by Quickstep192

Each of my guns has multiple tip selections and a guide to match viscosity to tip. At higher viscosities, even with the larger tip I was getting poor results. It was only when I thinned a lot and went with a small tip that I got good results.

Sounds like you've got that variable covered.

[Howard Klepper]

Originally Posted by John Arnold

A mix of 30% Piano Lacquer and 70% Stringed Instrument Lacquer seems to be a good ratio. Caleb Smith gave that formula to Mohawk, and you can now order it direct from Mohawk, using Caleb's name. Straight Piano Lacquer is very easy to work with, and builds quickly because of the high solids. But it is susceptible to cold checking and chipping because it hardens so much.
I also thin around 10% to 15%, using Mohawk reducer. I thin more when the temperature is cold, and less when it is hot.

I use them in about the opposite ratio. The knock on the instrument lacquer has long been that it is too soft and will feel soft when cured and not sand and buff as well as the harder lacquers. But the Mohowk/Behlens furniture lacquer is too hard and checks if built to the thickness needed for a glossy guitar finish. When I talked with their technical advisor about 5-6 years ago (when MacFaddens went under) he thought the piano lacquer alone would work without checking on an acoustic guitar. The piano lacquer has some plasticizers and is not as hard as their furniture lacquer; it is made for a thicker build. I tried it alone but did get some checking reported by a client (but no chipping). So far by mixing about 3 parts piano to 1 part instrument lacquer I have had no problems with checking. Been doing that for 2-3 years now.

[pickitluther]

I've talked to two different people at Mohawk and they have no idea at all about Caleb ordering this from them ! Caleb himself told me he orders it from them.
I talked to the person who is in charge of custom mixes and he tells me it's never been done !

[Quickstep192]

I have a regulator at the gun inlet, measured with trigger pulled.

[mirwa]

Any photos of your spray gun, I ask because none of my spray guns came with variable tip sizes to swap out.

My guns come with a specific needle and cap size, which can be replaced but you have to order them in.

Steve

[Quickstep192]

This Link below is the spray gun I have. It came with 1.2, 1.3 and 1.4 tips and I added a few when I ordered it.


http://www.tcpglobal.com/DEV-GFG-670...l#.WQCIBZH3af0



I also have a touch up gun that has 1.0 1.2 and 1.5 needle/tip/air cap sets.

[mirwa]

Good gun choice, are you using a 1.4 needle and cap

Steve

[GolfSteve]

Originally Posted by Quickstep192

Thanks for the replies. I'll definitely try the mix of piano lacquer and stringed instrument.

I tried spraying the Stringed Instrument Lacquer full strength, then at 20% reduction, then at 25%. It seemed that no matter what I did, I got a lot of orange peel and bubbles.

Long story short...

I decided to "go for broke" and tried a mix that was 50% Lacquer, 43% Thinner and 7% Retarder. It seems to be working. It seemed to spray easily and even though it builds very little per coat, I can probably do four coats per hour.

Is this too thin? Is there heartbreak waiting around the corner? Is it reasonable to think that I'll need double the number of coats that would have been necessary at full strength?

I think viscosity & retarder are not the problems. I've sprayed this stuff straight and/or thinned about 15% with excellent results.

However spraying is not easy and there is a learning curve for each finish...

First get the room temperature, wood temperatures, and finish temperature right. My room is about 20 to 22 deg C. Too cold or too hot causes problems. Too humid also causes problems.

Second, using a viscosity cup and your gun's operating manual determine the tip size that your gun requires. I gave viscosities for the finishes I use to my supplier and he recommended tip sizes for me.

Third is the hard part - and for me it was trial and error until I got the hang of it - you must develop your spray technique; and the technique might be different for different finishes. e.g. when I spray water based finishes, my gun speed is much (~50%) faster than when I spray solvent based finishes - because the water based solvent has higher viscosity and requires lower coating application thickness.

• If I hold the gun too close to the surface I get orange peel. My gun recommends 8" from the surface. Take out a tape measure and check how close to the surface you're holding your gun.
• If I spray a coat too thick I get orange peel (i.e. if I move the gun too slowly).
• If I spray with insufficient pressure I get orange peel/poor atomization.
• If I spray too many coats too quickly I run into problems - either orange peel if I go back and re-spray over wet surfaces (i.e. coating is too thick), or I've ran into a variety of curing problems if I didn't let the finish dry between coats.
  
• If I hold the gun too far away from the surface I get a dry pebbly finish.
• If I spray with too much pressure I waste finish and get too much overspray.
• If I spray too quickly the coat is too thin, it doesn't flow out, and I have to spray more coats to build-up.

I had a lot of trouble until I got the first two points right (holding the gun 8" from the surface and moving the gun at the right speed to get the right coating thickness). It's frustrating, but you must find the right combination of pressure, tip size, spray distance/spray speed/coating thickness that works.

Once you figure that out you can very good results from this finish.

p.s. like you I've found that I get better results using a smaller tip size and slightly higher pressure than my supplier recommended - but this is inter-related with viscosity and coating thickness. I suspect a professional using a larger tip and lower pressure can do the job much faster or with fewer coats than I can.

[Quickstep192]

Originally Posted by mirwa

Good gun choice, are you using a 1.4 needle and cap

Steve

I'm using a 1.0 needle and cap since I've got the finish thinned 50%. The finish is nearly water thin. I tried the 1.4 cap with the finish un-thinned, but I got a lot of orange peel. Even at 25% I got orange peel. That's why I went to 50% and the smaller tip.

[mirwa]

Just accept the orange peel, it's a product of the gun design.

What's happening re the multiple little air bubbles?

[Quickstep192]

The bubbles are gone with the highly thinned finish.

But, when I sprayed at higher viscosities, the orange peel wasn't normal HVLP orange peel (like you see on a car), it was much more pronounced and required considerable sanding, not to mention the bubbles.

I'm intrigued by the conventional gun. My volume is so low that I don't need to be concerned about material usage, but overspray is a concern. Hoping to give it a try this weekend.

[mirwa]

I found this image on my hard drive, I remember it being nitro and about 2 yrs ago.

Pretty sure this I was using a conventional spray gun on final coats, I know it did not get wet sanded or buffed prior to going to the customer, it was an off the gun finish.

For info, I have many spray guns for specific purposes and results



Steve

[Quickstep192]

Yeah, yeah, yeah... Show Off! 😀

I can only dream of an off the gun finish.

[mirwa]

Years and years of doing it, also have painted a few cars as well.

I was taught by my old man, he was a professional spray painter.

The point I and I think others are making, yes you can use a spray can, but in reality your skill set and finish wont improve greatly as you have no control over the mix and settings.

This does not mean a paint job using a spray can, cannot be done and cannot look magnificent, its all technique and skills.

Mixing your own paint and being able to manipulate the pressure its being applied and the spray pattern can only lead into better quality finishes.

Steve

[Quickstep192]

I sanded my earlier coats flat, then shot a couple of coats using my conventional spray gun. It was quickly apparent that the conventional spray gun layed down a coat without orange peel. I sprayed what I thought was a nice wet coat, but when it dried, it looked more like semi-Gloss than Gloss. It's nice and flat, but not glossy. What happened?