Spraying spar varnish with a hvlp system?

[eflanders]

Have any of you tried spraying spar varnish with a hvlp gun? I have a rockler 1000 hvlp system that i was thinking of using. I've never sprayed any oil based product through it though. What things should I know before trying this? Such as: clean up, thinning, etc.

[Ian McColgin]

If you're using a traditional varnish, you can't. You must go through some care not to introduce air bubbles as they won't vanish as the varnish cures.

You don't ever stir varnish with the thing on the end of a drill. I never stir at all, preferring to simply decant through a varnish filter into my hand cup. I use the decanting process for any thinning of early coats. But I have seen some good varnishers who very slowly hand stir.

When applying the varnish, you essentially lay it down with just a couple of strokes always toward and over the last area varnished. No brushing back and forth as that will introduce air bubbles.

There maybe modern varnish like products that can be sprayed, so check the manufacture's sheets. But real varnish, don't even think about it.

[David G]

I have sprayed traditional long-oil, phenolic/tung spar varnish, as well as a variety of more modern topcoats, with both a conventional gun (Binks 2001) and an HVLP driven by a compressor. Either works fine, and spraying is my choice for large areas, or for surfaces with tons of topographical detail - which are time-consuming to brush without drips or holidays.

But with a turbine-driven HVLP? Only tried it once, and it was a strong fail. Since then, I've come to understand that the majority of turbine systems (like yours) just don't have the oomph to atomize more viscid materials (like spar varnish, or latex paints). You could give it a go to see for yourself, but I'm not sanguine about success.

[MoePorter]

I've sprayed Epifanes varnish many times with my old Fuji turbine HVLP. Worked fine with several versions of their varnish. I used their thinner.Moe

[Ian McColgin]

Just goes to show one can learn something new. I've never before heard of success with sprayed on varnish. There is a yacht refinisher near by who always sprays large areas, like hull topsides, and who has done some hulls bright but she uses other clear coat products, not varnish.

Couldn't find a pic, but we've a lovely lapstrake launch in the harbor that's all varnished inside and out except for the anti-foul on the bottom. A friend who is a very skilled autobody guy lacquer who watched in disbelief as one of the yard crew brushed away and then looked at the other side to realize how perfectly it went on with no brush marks or sags or holidays.

With real varnish and perhaps with other clear coats, the reflective quality of the final coat is an important part of the UV protection.

[Skegemog]

sprayed trad varnish with an HVLP turbine to finish bright interior of a wherry once, it worked OK, but ad to really pay attention to thinning to get it to work. Definitely prefer gravity gun or even better air-assisted, airless tho the later wastes some material clearing the lines. Brushing is fun for the zen of it but a pain with too many protuberances

[Ian McColgin]

For those who spray traditional varnish:

How much thinner?

How many coats?

Do you 'hot coat'?

This is idle curiosity as I will never varnish again, "No Varnish" being Meg's motto. It's just fun to learn.

[MN Dave]

Ian is probably right, and David found out why. Thinning might work, but it might be more complicated than you would like. EDIT: 4 posts since I started, so let me add that Ian's questions are very good.

Spray paints have a mixture of solvents that dry at different rates. The fastest drying ones should mostly flash off as the spray is going through the air, which is why you don't want the gun too close to the surface. The fast ones are there to thin the coating enough to spray. the others are for leveling. Bubbles are a problem because varnish is viscous. Thinning will help there.

https://solvents.americanchemistry.c...-products.html

Many spray paint formulations contain fast, medium and slow evaporating solvents. The fast evaporating solvent provides a lower initial viscosity to make application easier; the medium evaporating solvent helps prevent dripping and sagging and the slowest evaporating solvent, the last to leave the system, finalizes flow and leveling to promote a uniform film thickness and ensures the paint sticks to the substrate.

The trick is to figure out what mix and in what proportions will work. I would have to use trial and mucho error to figure out a workable mix, and it is a safe assumption that the solvents for varnish and rattle can paint are different. Rattle can solvents were easy to find. A Rustoleum aerosol spray paint (first list on google search) has a mix of:
Boiling, solvent
-42 LPG propellant
56 Acetone
80 Methyl Ethyl Ketone
126 n-Butyl Acetate
136 Ethylbenzene
140 Xylene
171 Propylene Glycol Monobutyl Ether

My first guess with a low level of confidence would be something like acetone, MEK, xylene and D-limonene. HVLP might not need the acetone. D-limonene boils at 176, is a lot like turpentine as a solvent and should be easier to get than PGME. On second thought, maybe just xylene, then go complicated if it doesn't work.

[Robert W. Long]

In the 90s I sprayed a fair amount of traditional spar varnish with my hvlp setup with great success. I always sprayed the first coat thinned half with paint thinner. The only problem I had was dealing with the stickly mess of overspray which I solved with Dexter like use of clear plastic sheeting. And no hot coating. I gave at least 24 hours between coats sometime more.

[David G]

For those who spray traditional varnish:

How much thinner?

How many coats?

Do you 'hot coat'?

This is idle curiosity as I will never varnish again, "No Varnish" being Meg's motto. It's just fun to learn.

How many, and which, thinner depended upon the brand. Some I use only whatever proprietary thinner they specify. Some are more viscous than others, and require more thinning to get to a sprayable consistency.

How many coats depended up the client, her fussiness, or his budget. Won't do less than 6, with the first heavily thinned.

Yes, I have hotcoated. But not so much to gain overall calendar time, as one has to allow for extra cure time after the second coat to avoid entrapment. Instead, it was mostly to save a round of both gun-cleaning and dust-fussiness.

I have heard other tales of success with a turbine HVLP... but I've heard far more of 'not enough oomph'. I've not checked the specs, but I always had the vague impression that the Rockler was not the most robust of units. Could be wrong. But it's a demanding use of a turbine, at best. It's likely to take someone with a bit of savvy (or a bit of luck?) to make it happen. Do you own and use a Mil Gauge? How about a Zahn #2 viscosity cup, or similar?

[L.A Marche]

I’ve been spraying with a HVLP turbine gun for almost 30 years, I’ve never sprayed varnish but I’ve sprayed poly urethane clear, latex/acrylic and alkyd paints, nitrocellulose and water based lacquers, shellac and shellac based primers.
A few things I’ve learned:
Needle size is very important, the thicker the material the bigger the needle.
Use the manufacturers suggested thinner type, water, alcohol, lacquer thinner, paint thinner etc.
Use a short air supply hose, there is a lot of friction in those one inch hoses.
Do not spray cold finish, room temperature or above.
If you thin, do so in small increments and test spray before adding more thinner. Don’t over thin the final coat as it might affect the final sheen.

[Jay Greer]

I have used a spray gun for many jobs in the past but, when I think of all the masking that must be done and the time it takes to mask I tend to lean back to laying varnish on with a brush. That is the only time I get some rest! Cleaning out a spray gun is not my thing! Plus, my Russian boar hair Linzer Varnish Brushes are now sixty years old and just getting broken in!
Jay

[Don Z.]

There is some good info above, but I think a point that is missing is that Epifanes makes a thinner explicitly for this purpose. It may be worthwhile to call their Technical Support.

http://www.epifanes.com/page/spraythinner

http://www.epifanes.com/page/contact-us