Spraying WB Poly; questions from a new sprayer

[Hugh MacDonald]

I'm new to spraying and recently acquired an Accuspray three-stage turbine rig. I'm going to be spraying Target Coatings WB 9000 Super Clear Polyurethane on maple cabinet face frames and carcase parts. Naturally I have loads of questions about spraying and need to do a lot of practice first to help answer those questions, but I was wondering if anybody who has sprayed WB polys or similar WB products has any advice on optimal gun setup to get started with.

The Accuspray came with two sets of needle tips/nozzles and two aircaps, the 1.1mm (43) and 1.3mm (51) needles/nozzles and the 5 and 7 aircaps. According to the Accuspray manual the 43 nozzle is suited for "medium viscosity materials" while the 51 is best for "heavier viscosity materials" without giving much else in the way of viscosity specs in Zahn seconds or otherwise. The 5 and 7 aircaps, meanwhile, will give you "no orange peel" and "almost no orange peel," respectively. Based on your experiences and the viscosities of the Target EM9000 and other WB polys in general, what would be a good starting point on nozzle and aircap setups with these products? I understand that most of spray-finish quality is going to be based on practice and experience; I'm just looking for the best starting point, based on what I have, so I don't waste too much of the Target EM9000 before getting up to speed.

Also, for future reference (I'm interested in spraying lots of product now that I have a sprayer, and the various Target finishes get really positive endorsements here), what setups do you use when spraying WB "lacquers," varnishes, shellacs, paints (or the tinted Target EM6000 series)?

I'm also in the middle of putting together a shopmade spraybooth to be used in the shop. What, in your opinions, would be the minimum CFM requirement for an exhaust fan, for spraying exclusively WB finishes. I've seen a lot of numbers offered here from guys who set up their booths, from 2200CFM to 6000CFM, so I'm not sure what basic requirement would be for efficient removal of fumes and particles. Can it become a problem when you're moving a lot of air, at relatively high speed, across your workpiece, such that the fan pulls your finish away before it has a chance to land upon the workpiece?

Many thanks for your help.

[Jim Becker]

I'm not familiar with your gun, but with my HVLP conversion gun, I use the same setup for all of the Target Coatings products I spray as well as for shellac. For my Wagner gun, that's a number 2 cap with a #3 needle. I believe that's close to your "43". I suggest you try that with the 5 cap and see what your results are spraying on some scrap for practice. I can't help with any turbine adjustments since I don't use one...

[Hugh MacDonald]

Jim, thanks for the response. I was hoping you might add something as I've seen your posts on other finishing threads and you also recommended the Target finishes. I've been doing a little spraying on scraps. It's been hard to tell the difference in result between the different nozzles and aircaps. Both setups seem to atomize the finish well. But I can say that the result, so far, is not very good. The finish is a little bit rough. I'm experimenting with lighter and heavier coats, although the can recommends spraying a 1-3 mil coat, and that's what I would call a light coat.

Do you guys thin the EM9000 poly a little bit for spraying? Or go with it right out of the can?

[Jim Becker]

In general, water borne finishes are not really designed to be thinned. You have to remember that the water is a carrier and not the solvent for the finish. When you add more water (or other liquid) to "thin" the finish, you're spreading the actual finish molecules out farther. You can thin a finish like shellac and solvent-based lacquer much easier in that you reduce them with their own solvents. With water bornes, about 10% is the limit and IMHO, best results come from using them in their "out of the container" consistency unless the manufacturer suggests otherwise.

For what you describe, the remedy likely has to do with gun adjustment. An additional challenge is that a turbine's air tends to be much warmer than compressor air, so it's also going to have an effect on spray settings. That said, laying down coats of finish out of any gun requires some practice to get the "feel" of how the finish sprays, both for gun settings and how you move it during the process. I know that on my gun, for the finishes I actually spray, I need my gun's adjustment for how far the trigger moves the needle to be set at exactly 1.5 revolutions from closed with the air pressure settings I use for my dedicated spray finishing "drop" and the regulator on the gun. That took me time to get worked out, but it's been remarkably consistent over the long haul. I think you need to get a little more finish coming out of your gun to try and avoid it going down too dry and feeling a little rough. There has to be enough of a wet coat that it can level before it dries appreciably and that may be what you are noticing as an issue. Experiment. Yea, it cost a little for the finish, but the goal is to get a setup that's repeatable which saves time and finish in the long run.

[Tim Howell]

You never gave the dimensions of your finishing room in cu ft. Can’t help but think it would make a difference. 6x10x 8 just don’t setup the same as 20x20x12 room.

[Hugh MacDonald]

The spray booth area is about 6' x 6' x 7' with one open side, to allow for airflow. In other words, not totally enclosed.

[Mark Kornell]

6x6x7 = 252 cu ft. You want to size the fan to be able to recirculate the room about 3 times a minute, so a 750 cfm fan should be adequate, in theory. Add in some filters before the fan, and up that to 1000 cfm - in theory. In practice, with an open side to the booth, you need more cfm, but how much depends on how close to the fan your work will be, the shape of the booth, the size of the overall room is, and where the make up air is coming from.

Too much airflow is a problem, in two ways. First, you want your finish to land on your work without airflow changing its direction or sucking it away entirely. Ideally, only the overspray gets sucked away. When spraying, it is fairly important to have a consistent and even spray pattern landing on the work, so the fan shouldn't be affecting the airflow too much. The second reason is that excessive airflow will cause your finish to dry faster, which lessens the time it has to flow out, which can lead to orange peel.

Personally, I'd go with a 2000ish cfm fan, and experiment with workpiece placement. If you have the ability, place the fan at a lower level than the spray table - gravity is your friend in carrying away overspray.

[Mark Kornell]

And, to address the question of spraying the Target 9000sc - I've sprayed a few gallons of both the gloss and satin direct from the can using my Iwata LPH-400LV. I use a 1.4 mm needle/nozzle, and it comes out like glass. It goes on a little pebbly, but as it dries it flows out dead level after about 20 minutes. Spray two coats on subsequent days, then on the 3rd day, light sand to remove dust nibs, then a final coat. I did try spraying with 1.3 n/n set, but didn't like the results quite as much. My guess is that the 1.3 n/n over-atomized the 9000sc, and while it went on in a finer spray, the smaller spray particles dried faster, not giving it enough time to flow out completely. Probably could have dealt with that by upping the material flow on the gun, or laying on a heavier coat - hard to experiment since you can't tell what the ultimate results will be for 15 or 20 minutes, so I just went back to the 1.4 with gun settings I knew would work.

There is tons of information on the Target Coatings forums, and Mr. Target - Jeff Weiss - seems to be readily available to answer questions.

Haven't sprayed Target's WB shellac, but I do spray a 1.5# shellac I mix myself. As it is considerably less viscous than the 9000sc, I use a smaller n/n. The smallest I can get for the Iwata is a 1.2mm, but a 1.1 or even a 1.0 would likely work better.

[John TenEyck]

I use a temporary spray booth about the same size as yours, also open on one 6 foot end. I had a 400 CFM fan venting it to the outside, and that was OK except when I sprayed large projects. Continuous spraying would slowly overwhelm it and eventually fill my shop with overspray; however, I never really had a problem with overspray leaving a rough surface on my project. I recently went to a 1200 CFM fan (my dust collector, actually - I bypassed the bags and vent it directly out a window) and it is almost too much capacity. I had to install a baffle plate in front of the inlet to keep it from sucking finish away from the work that was at that end of the booth. But it works great, and I can spray continously with no overspray getting out of the booth. Note: I only spray WB products.