***New Article*** *LINK*

Re: ***New Article***

Stuart Hough

Thanks, Mark and Ellis! This article has exactly what I needed to assist me in deciding what system to use for my spray finishing (when I get to that point)! And as any tool nut would agree...I need all three! In all seriousness, though, I think the mini-gun system and the conversion system will be more cost-effective for me. Thanks to Mark for doing the comparo, and thanks to you, Ellis, for this site, where I have gotten the best info I could have found on this and many, many other aspects of the craft!

Re: AMEN!!!!

Larry Rupprecht

Mark's report is just what the finish-doctor ordered. I will always be too frugal [cheap] to spend the money needed without having an unbiased opinion that is based on experimentation. ....just another problem for the science/engineering schooled crowd I am part of!

Excellent work. I am expecting my finish quality will see improvement soon.

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Kneale Brownson

Click the Red WC button, look through the Home Page info for the "Support WC" link. I signed up for the PayPal version years ago.

Conventional vs HVLP

Bill Tindall, E.Tn.

HVLP is not the only choice. Some insight why you chose HVLP over conventional would aid those contemplating using spray for finishing. Is there any advantage beyond less overspray?

I never miss an opportunity to encourage serious woodworkers to learn to spray. I was lucky to get started with a mentor that worked in the tech service department of a supplier of wood finish products including CAB lacquer. I missed the frustration of wiping and brushing and gained the ability to use lacquer and conversion varnish in addition to all that is brushed.

What is the compressor requirement for your conversion gun? If I understand what you mean by conversion gun it may be equivalent to the Apollo I bought, and quit using. Mine requires an amount of compressed air that only those driving a ROS sander will have.

That Ain't All

Mark Mandell - Gone Round In New Jersey

WC, like most all websites, runs on the advertising revenue it generates. Ellis has a fine group of sponsors, but their contribution depends on their ads pulling in business. If you are going to buy stuff from any one (or all) of the companies you see on the top or margins of the message boards or the Marketplace page, go to them through the WC links in the banners and logos rather than on your own! That way WC gets credit, and the companies maintain their sponsorships of this great resource.

Several Things

Mark Mandell - Gone Round In New Jersey

Less overspray is only part of the advantage. Transfer efficiency is much better with HVLP because the droplets are driven to the surface much slower, reducing bounce-back; you get better coverage with less product and less waste. My Walcom is most efficient with pressure in the low to mid 20's. The CA Tjr works best at 10-15 psi with the compressor's regulator set at 40psi. Both of my conversion guns will run off my 2hp 6cfm framing-nailer compressor. They do much better, however, hooked to the big IR (3 hp/80 gal/12 cfm) compressor because the large storage evens out the compressor pulse for a smoother application spray.

I've heard very good things about the Apollo "Atomizer" conversion gun and was tempted to buy one to untether from the pressure pot on medium size jobs, but rigging up with a PPS cup on the Walcom was easier and cheaper. If you were trying to run that Apollo at the same pressure you use with a conventional gun, I'm not surprised you didn't like the results; no doubt you were overloading the needle and air cap. Try it 20 psi.

you named only one

Bill Tindall, E.Tn.

Overspray, transfer efficiency....it is all the same metric and it is better for HVLP which is why, in the face of otherwise just fine spray technology, HVLP was mandated in CA. Otherwise I doubt it would have ever been developed. Your presumption of why I stopped using the Apollo gun missed the mark. I have been spraying furniture for decades and I always read instructions for new equipment.

I will pen an alternative to HVLP soon with many advantages of conventional over HVLP. Few of us can find any significant benefit from just better transfer efficiency. I found HVLP better for the insides of drawers and no where else.

One was Enough I Think

Mark Mandell - Gone Round In New Jersey

Transfer efficiency is, in my world, the name of the game when spraying finish.

The rest of my response had to do with your complaint about necessary CFMs.

So what, exactly, did you dislike about the Apollo? What finish were you using and what was the sub-parr result? I used to rub out finishes, but the Walsom gives results "off the gun" that make further treatment unnecessary.

Re: you named only one

Larry Clinton At Frankfort, (Central) Indiana

I have to agree with Bill, I have several conventional guns - mostly Bink's and a couple of cheaper HVLP guns. I also was responsible for setting up some spray booth operations when I was working as a manufacturing Engineer prior to retirement. At that time I experimented with conventional guns, HVLP, and Airless systems.

Transfer efficiency is NOT an issue for me - nor is over spray. I do not use large amounts of finishing materials. I can spray a far wider viscosity range of materials with my Bink's guns than the HVLP units.

I can far better control the atomization with the Bink's guns and obtain a fine finish with thicker and finer material. This is important to me as I can vary the amount of solvent and retarder to obtain the results I want when the temperature and humidity varies.

I do use the HVLP occasionally when I have to spray into a deep shelving or chest interior. Normally I spray the inside of these and then switch to conventional for the outside.

Not My Job

Mark Mandell - Gone Round In New Jersey

to do a whole treatise on the range of spraying equipment available. My stated purpose was to compare conversion gun HVLP with a currently available quality turbine driven system; nothing more.

I am not advocating that any given type of sprayer is better than any other nor do I have either the time or the inclination to get into a debate on the subject. "If you like your _____, you can keep your______."

While I haven't looked, I'd be very surprised if there aren't any number of Internet forums running where spray painting aficionados can come to blows over whose rig is best.

Personal preferences aside, I've no doubt that the various equipment options work better than others given the range of coatings in use and the item being coated. Over the last 50 years I've had occasion to use conventional guns as well as airless spray equipment.

For what I do, what I have does what I need and want.

my experience agrees with all your points

Comparing HVLP vs Conventional

Bill Tindall, E.Tn.

This discussion is a good practice run at a future Article on conventional spray guns.

If your only exposure to spraying finish is from woodworking stores and popular press you might conclude that HVLP technology is the best, or even the only way to go. Those contemplating acquiring spray capability should have all the data, and encouragement to learn to spray. Conventional spray equipment has its advantages, discussed below.

I use a suction feed DeVilbiss JGA 502 with a #30 cap and the 3M PPS system with the full selection of cups from 100 mL to 500 mL. I spray conversion varnish, oil based paint, oil based varnishes, stain, shellac, Target water based finishes, automotive finishes-in about that order of frequency. The selection of PPS cups makes it practical to finish large surfaces or do detailed touch-up and stain shading with my gun. The PPS cups allow spraying in any gun orientation, even upside down, and easy cleaning. The smaller cups result in a compact assembly that is easier to navigate among furniture parts to be finished, an advantage not to be overlooked.

Disadvantages of Conventional

1. Complexity DeVilbiss made/makes numerous guns that to my eye look the same as the JGA 502. Repeat for Binks and then add other lesser known makers and knock-offs from Harbor Freight. For each of these guns there is a cap and needle that must be selected for the spraying task at hand. Without expert help from Devilbiss tech service, or the aid of the person in your nearby auto body supply shop, the beginner may not get a gun that works optimally for their needs. I was lucky when I started. A professional finisher said, “buy the 502 with a 30 cap”. This combination is optimized for lacquer but it works well for what I spray. There are equivalents. The challenge is to find someone to help make informed choices.

2. Transfer efficiency HVLP transfers somewhat more finish from the reservoir to the furniture. The result is somewhat less overspray and substantially less-blow back when spraying inside corners, or insides in general. The transfer efficiency difference isn’t that great. The amount of stuff we typically spray over the life of our equipment is not enough to generate an economic benefit for HVLP.

Advantages of Conventional

1. Cost Almost any air compressor is adequate to spray furniture with a conventional gun. I have sprayed a door, on site, with a tiny compressor used to drive a pin nailer. Used guns are readily available on Ebay and elsewhere. Son-in-law bought a JGA 502 that had hardly been used for $50.

2. Learning curve I often spray stuff for those that don’t have the equipment. I will usually get the project started and by the end I have them spraying their work. Finish viscosity, air pressure, flow and fan adjustments, and distance from the target are all critical variables in getting a good result. It is generally accepted that convention guns have a much wider acceptable range for these variables. I tried HVLP with a high quality Apollo gun. I found that I had to be more careful adjusting these variables with this HVLP equipment. I got acceptable results with conventional or HVLP but there is no doubt which I would prefer for teaching someone new to spray finishing.

to answer your questions

Bill Tindall, E.Tn.

Transfer efficiency has no relevance to my spraying needs. The technology has to have some other advantage to kindle my enthusiasm, and it doesn't. Equipment cost and learning curve can be significant disadvantages.

"So what, exactly, did you dislike about the Apollo?" I could get equivalent results with conversion varnish but the latitude for variables was tighter with the Apollo gun. I realized the cost benefit (transfer efficiency) I hoped for was not worth the extra effort using the Apollo. Navigating the DeVilbiss with small PPS cup around furniture was a more pleasant task.

" I used to rub out finishes, but the Walsom gives results "off the gun" that make further treatment unnecessary. " This statement is puzzling. When I get orange peel I add a retarding solvent. I don't consider the effect has anything to do with the gun adjustments, at least within the latitude of typical. But then, many agree that atomization with conventional is easier to achieve.