Official Luthiers Forum!

I'm using a nice gun prolly 1-2 mm tip, HVLP. I am trying to achieve a wetter application. Seems my stuff dries pretty quick. Thoughts? (Mohawk Nitro, Behlen formulation)

do you use a wet film thickness gauge to know how thick you are spraying?

_________________
http://www.Harvestmoonguitars.com

No. I don't know what that is. But I can assure u I am blowing a lot of finish because it is too dry.

you can get them for free at a lot of paint stores or have amazon deliver one for about $10 https://www.amazon.com/82-479-Film-Gauge-1-80-Scale/dp/B01BM7MU02. It allows you to measure the film you are laying down. I check it out on a test panel using the same spray pattern I spray with. It is is handy to know because with that information and the percentage of solids in the lacquer you can calculate your dry film thickness.

You are asking formulations I would be questioning my gun setup first.

_________________
http://www.Harvestmoonguitars.com

How quick? Is it dry spaying on the surface? Could be gun set up, could also be application technique..... Make sure your gun is set up properly first like I show here https://howardguitars.blogspot.com/2015/06/spray-gun-setup-technique-by-brian.html

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Follow the gun setup on B. Howards link first. I use Mohawk Piano Lacquer but I build solid body only. I would use the Stringed Instrument lacquer for hollow body guitars. Either Mohawk or Behlen which is Mohawk anyway. They are designed to spray without thinning. Thinning gave me problems.
http://www.luthiersforum.com/forum/viewtopic.php?f=10123&t=51785

What gun? Conversion or turbine? There is a big difference between a 1mm tip and a 2mm tip...what tip set is recommended for your gun when shooting lacquers?

_________________
We have become a civilization that elevates idiots, prostitutes, and clowns. Am I still to defend it? Yes, for its principles. Yes, for what it was. Yes, for what it still may be.

-Mark Helprin, The Oceans and the Stars: A Sea Story, A War Story, A Love Story (A Novel)

I had a can of retarder. Seemed to solve the problem. the gun is an Italian thing... remember in morn. Love it though, not turbine, not conversion, true HVLP

If what you mean by "true HVLP" is a pressure pot and two hose to the gun type, you might want to try running some thinner through the fluid hose to clean it out to allow more fluid flow. You might also check that the regulators are working properly. Generally dry films are from too much air in the air/finish mix or spraying too far away.

I am happy you got things to work with your existing spray rig.

Your gun is likely a conversion gun, which just means the low volume, high pressure air from your compressor is converted to high volume, low pressure air in the gun, versus a turbine HVLP gun, where the HVLP air is generated external to the gun using a single or multi-stage turbine. While both types are essentially identical once the HVLP air is mixed with finish and applied, they have some unique issues (e.g., drying and cleaning the air for a conversion gun; cooling the hot, very dry flow for a turbine gun), so worth knowing which type.

I'm not certain 'true HVLP' is not a marketing term - compliance is more the concern with HVLP spray guns, as in compliance with 40 CFR Part 63 rules which apply to the spraying of VOC and HAP-containing finishes. The usual guideline cited for HVLP is a tip pressure of 10 PSI or less, but there are a number of ways to get there.

_________________
We have become a civilization that elevates idiots, prostitutes, and clowns. Am I still to defend it? Yes, for its principles. Yes, for what it was. Yes, for what it still may be.

-Mark Helprin, The Oceans and the Stars: A Sea Story, A War Story, A Love Story (A Novel)

Might be like swatting flies with dynamite... retarder is heavy and should only be used in modern nitro formulas when absolutely necessary. You have likely added a few weeks to your cure to buff time as it will take a while for that to gas out.

True HVLP? I have used many different designs of that over the years. From guns that look like siphon cup guns to Gravity fed. HVLP Deals mainly with the airflow through the gun, High volume of air at lower pressures to accomplish atomization as opposed top older guns that ran at higher pressures. IME the HVLP guns that are not gravity fed and are not actually pressure assisted with pressurized cups never work well.

The two hose deals with the separate head and pot are usually air over pressure or "air assisted" With most of the spray force derived from fluid pressure and a bit of air fan at the cap to just atomize, not transport the fluid. These are the peak of transfer efficiency and can be dialed in to match product instead of adding reducers and such to make product work with equipment.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

I use a Husky HVLP from Home Depot with a 1.4 mm tip. It basically looks like a standard oldschool spray gun with a gravity feed cup to me. Anyway it works fine. It came with a 1.8 tip also which I have never tried. Some people call them jamb guns too. I think it was around $50.
I don't know what the real expensive guns do differently but since I level sand before buffing anyway I couldn't see a reason to go off for the big bucks. Maybe someone on here can explain the difference.

Maybe your psi is to high. I spray mine under 30 psi depending on humidity.

_________________
Jason Moe
LaCrosse WI 54601

Are you using the best thinner you can get? Better thinners have more of some expensive ingredients that make it easier to get a good flow out. I go to a store for professional finishers and ask for their best lacquer thinner. In balancing all the variables like pressure, gun adjustments, distance of gun from surface, speed of moving the gun, amount of thinner, etc, the good thinner makes it easier to find that "sweet spot" where the finish flows out to a nice gloss and it is easy to avoid runs.

The stuff in the hardware store is only good for cleaning equipment.

What Leonard said.