Matching the Spray-Gun to the Finish
A discussion of pressure-pot, airless, and air-assisted gun choices, focusing on which rig is best for applying which type of formula. July 17, 2008
I have a well-established custom cabinet building business, and in the last couple of years I have been offering my cabinets finished, rather than site finished, mainly for the increase in remodels, and also as a profit facet of my business. I do mainly stain, seal, semi-gloss lacquer, and the occasional paint/glaze finish.
I have been using gravity feed spray guns, a 1.4mm to apply stains, water clear sealer and clear coats, and a 2.00mm to apply primers and paint, mostly alkyd oil base and latex finishes. I get great results, but thought of switching to a pump, Kremlin, Graco, Binks, or other... Spraying these type coatings, what would be my best option - pump with air assist, pressure pot, multiple pressure pots, airless?
I would like something that would be quick to change finishes - sealer, clear, etc., possibly through a manifold with ball valves, drawing straight from 5's on sealer and clear, and a third on the manifold for flushing solvent. I think I currently waste a lot of finish and solvent on changeover and gun washout.
I run maybe a house of cabinets a week - mostly thermofused clad cases with matching edgebanding and finishing doors and end panels separate. Also thoughts on curing lamps, conveyored oven, or other to speed moving through the drying racks. Eager for your suggestions on a workable system.
From contributor R:
If you are looking for quick and cheap, then go to Home Depot and get two $300 a piece airless paint sprayers with 25ft hoses. Get 208 or 210 fine finishing tips for spraying. Use 1 for clears and 1 for pigmented. If you have a small job, then use a 2qt pot and gun. Smaller than that, use the gravity gun. If you were using a high dollar finish like WB or conversion varnish, then the Kremlin would be worth a look.
From contributor C:
I still believe in pressure pots and cup guns, so others will have to answer the AAA and other types. That said, I find I can adjust the pots to whatever I need to do, from light dry/mist coats to as heavy of a coat as I want, though the best pots are going to cost you quite a bit (Devillbiss, Binks, etc.). There are other good pots out there such as Astro's 2 and 5 gallon air agitated models that are an excellent buy. Mine are 5 years old and still working fine. The only thing changed is regulators. The 5's are great for putting 5 gal pails in, as are the 2's. The 5's are reserved for my main sealer and top coat applications, with the 2's for primer, color, stain/glaze, and 2 for specialty coatings. The cup guns are also one-item guns set up for further stain/glaze apps, bleach, retarder, metallics, pearls, shellac, polytung, and others. All together I have invested about 6 K in 6 pots and 20 guns and accessories. If I had to do it all over again, I would not change a thing, and I will continue this way if I need more in the future. All the Astro cup guns are fitted with Devillbiss TLC cups for easy cleaning and the pots are Teflon lined also. I rarely have to stop and clean any spray equipment out because of my setup, and waste is nil. With the type and amount of painted faux finishes and high end naturals I do, I need as much flexibility as possible and this system works better for me than any AAA, airless, or pump system I've ever used, except for the Poly Pro plural component system I used to have for polyester work.
From contributor P:
Some of your choices/goals conflict with one another. Having a single system with the ability to siphon from 5 gallon pails with quick and easy cleanup (switching between the various coatings) is one of the strengths of an air-assisted airless (AAA) pump system. You also get the ability to spray much faster than you're used to with excellent atomization and less overspray.
But... the AAA spray system is not a good choice for spraying house paints. These paints are designed to be applied by brush or roller and are so thick that they will bog down the AAA pump. It takes a lot of thinning to get them to go through the pump, which is counterproductive since you'll have to apply extra coats to get good coverage. And there's the concern that over-thinning latex paint can weaken its durability properties.
If you want to stick with the house paints, an airless sprayer is the better choice. These pumps work at much higher pressure than a AAA and are able to spray the paint easily and very fast. Cleanup is not as easy and switching betweens pails of material would be more time consuming.
A pressure pot is very versatile, since you can spray a wide range of materials with the right spray gun (e.g., Binks 2001). You will need to swap out needle/nozzles to fit the viscosity of the material you're spraying or have 2-3 different pots. Cleanup is just a little more work than it is for a cup gun as long as you use disposable pot liners.
My preference would be to use spray finishes instead of house paints along with the AAA pump and manifold you mentioned. You can get lacquer or conversion varnish to match any paint color and use that in place of the latex and oil-base paint. Or you could use a waterborne spray paint in place of the latex and CV in place of the oil-base paint. Switching between waterborne and solvent based finishes does add a couple extra steps in the cleaning process that could be avoided by sticking to all solvent based finishes.
From the original questioner:
With the pressure pots, is it possible to leave them set up - dedicated for sealer or top coat - utilizing two pressure pots? With the pump, the same scenario - close the sealer valve, open the clear valve, flush into the sealer container until you are pumping clear? Also, is thinning the material for flowout necessary with either system?
From contributor C:
On the pressure pots, yes, you leave them set up for sealer in one, top coat in the other. If you're using more than one main topcoat but not as much, you can get the two gallon size for those. There is no cleaning out when using dedicated pots, but if for some reason you have to, it's easy to do, especially with the Teflon lined types. I normally come in to work, turn the air on, and then the pot agitator is on and by the time I'm ready to start - 15 or 20 minutes - the material is stirred and I just turn it way down to keep it stirred the rest of the day. All the sealers, sheen coats are perfectly maintained this way.
Thinning/reducing is only necessary when there are wide temperature swings, as would be just as true of AAA or airless. The reason I don't use AAA mainly is because I do a lot of glazes and special affects that I can't spray - flash/mist/dry - coats on without disturbing the effects I create. They're just not good at that or creating high end Baker/Mastercraft/Karges types of clear wood finishes. For stain/sealer/tone/topcoat situations, I know they're the type preferred by many here, but I find the pots much more versatile than any of them. For the price of a first class AAA pump/setup, I can buy three dedicated 5 gal pressure pots dual regulation/air agitated - VS - 1 all purpose pump system.
From contributor L:
I am 1000% with contributor C on this. I have 6 pressure pots and about 5 gravity cup guns. The thing is, I might have $1000 sunk into 3 Kremlin pressure feed HVLPs and 5 pressure feed Walcom Geo 1.7 fx97s. All of these on Speedaire pressure pots. EBay - if you know what you are looking for, it is there. Every finisher must value flexibility in all its meanings. The pressure pots can blast full viscosity wall paint with the right fluid passages, and spray the finest of ultra thin off the gun table top finishes.
From contributor S:
With contributor R. If you want speed, go airless with a 209 or 311 tip and turn the pressure all the way down. You have to move fast, though.
From contributor H:
With all the different types of coatings out there, go with stainless. I use acid cat products. Learned the hard way when a clear job went south, the interior of pot was a mess. Once and done, stainless all the way.
From contributor P:
A pressure pot won't blast full viscosity wall paint. I've tried, and it's too thick. I have sprayed a lot of Polomyx, which is a very thick textured wall coating using a pressure pot, but unthinned latex is just too thick to spray well.
Pressure pots are more versatile than most spray guns because you can adjust the pressure that forces the coating to travel through the fluid hose to the spray gun, but there is a limit. If the coating is too thick, it won't come out of the nozzle at a decent rate, even if you use the largest needle available. And it takes a lot of atomization air pressure to break these thick coatings into fine enough droplets to get a smooth result.
No one system is the best in every situation. For speed and excellent results with spray finishes, AAA is a top choice. A pressure pot is a drop-in replacement for a regular spray gun with the added benefit that you can spray a lot more material between refills. And you don't have to hold the weight of the finish you're spraying, since it's in the pot, not the spray gun cup.
Neither AAA or a pressure pot is a good choice for spraying house paint. If you want to spray house paint, get an airless rig.
From contributor C:
I can't speak for the largest fluid tip and needle assemblies, but I can tell you that at OSF, I had a 1'8" setup on the Devillbiss guns for unthinned latex for Abercrombie and Finch storefronts that laid it on with no problem at all. Also sprayed textured latex and asphaltum, mastics, and others - no problem. If you'd like to see the results, stop by any of the pickled pine storefront locations nationwide and look at the painted glazed work inside. Other specialty finishes included the textured columns at the Structure stores, and the columns in all the Limited/Express stores. There is no coating used in the wood industry that I've run across that cannot be sprayed from a pressure pot setup. I also had one specialty Binks gun with a 1/4 inch fluid tip for spraying Seagraves polyester textured coatings - the ones with the 1/8" pieces of colored poly granules. I don't think the questioner plans on spraying any of the ones I mentioned outside of oil base or latex - it surely can be done.
From contributor P:
I'll guess you meant 1.8mm instead of 1'8" (1 foot, 8 inches) and that you were referring to the size of the opening in the fluid nozzle. On that line of thought, the 1.8mm needle/nozzle will allow thicker coatings to flow than a smaller size will, and a 2.2mm N/N will allow even thicker coatings to flow. But you still have to get them to flow at a rate that's fast enough to pass for production spraying while achieving good enough atomization to produce a smooth, flat finish. You can't get good flow rate and atomization without significantly thinning house paint. A little research into the rheology of the paint will clarify why this is true. Yes, it's possible to spray really thick stuff using a pressure pot system... The rubbery liner you see on pickup trucks is a good example. If your spray apparatus has an opening that's large enough and you don't need to atomize the coating, you can spray pretty much any fluid or paste.