Hi everyone-
I recently made the decision to spray my furniture/cabinets (with lacquer). Since I am relatively new to the spray gun, I have been spraying my pieces prior to assembly (with proper masking of appropriate joinery areas). I would like to make the switch to spraying assembled work – especially when it comes to cabinets. Any suggestions? I’ve read a couple of books on spray finishing (including Andy Charron) and have been following the advice on order of motion and technique, but still seem to be getting runs and sags. Am I simply “putting it on” too wet or ??? Would love to hear what works for others..thanks..
Replies
If you are getting runs, you are putting too much material on either in one or successive coats. This could be from holding the gun too close, and/or, too much thinning of the product. What product are you using and are you adding thinner or retarder? What type of gun and what size tip?
You probably understand getting the right fluid/air mix from your reading. If you are using HVLP, they often spray a round pattern which can take some practice with overlapping. It's also easy to linger when you stop at inside corners. If the problem is mostly in corners, you may have to let off the trigger a little earlier. Sometimes small changes in air pressure as well as adjustments to the fluid control can make a difference. Keeping the gun the right distance can be an issue also, too close and the air will blow the material around.
Lacquer melts into previous coats. Too much material will activate the first coats and then they act as one. Thick build up with lacquer can cause future crazing problems also. The old time 10 coat applications were done with a conventional gun and put on whisper light. Hvlp puts a lot of material on in comparison. Often two coats is plenty. I think you will get better looking and lasting results by blocking out the finish and polishing rather than trying to get a mirror finish off the gun. The more you build the more likely you will have problems. Anything beyond 3mils is unnecessary for most work. I only say this because that was the mistake I made when I started, over doing it. This site has some good information.
http://www.seagravecoatings.com/Trouble2.htm
Every finish handles a little differently and will vary with how heavily you can apply them before they sag or run. I think the best approach to getting started spraying is to use the same finish all the time, keep it the same temperature all the time, and thin it the same amount all the time. That way you will master that finish and eliminate the variables that would require you to adjust your spray technique.
Thinning and temperature affect viscosity (how thick or runny the finish is). Thinner (watery) finishes need to be applied in thinner coats and vice versa. As the temperture of the finish goes down, it will become thicker and spray differently... you'll have to spray a little slower and/or increase fluid flow and atomization air pressure. Maintaining the finish at the same temperature all the time keeps the viscosity stable so it sprays the same every time.
Thin the finish as needed to get good fluid flow and atomization (fine mist). The more you thin the finish, the more it will want to sag and run so you'll have to spray light wet coats.
Now it's just a matter of practice. If at all possible, use a side light to reflect off the surface you're spraying so that you can see each spray pass. One of those flood lamps on a stand works well for this. Your goal is to lay down light, overlapping, even wet spray passes that flow out to form a continuos film. Maintain a consistent distance from the surface and hand speed as well as the amount you overlap each spray pass.
If you want to get more scientific about it, you can measure the viscosity of the finish you're spraying as well as how thick you're spraying each pass. There's a desxcription of the process at this link - http://www.finishwiz.com/viscosityandwetmils.htm
In the mean time, there's some info on repairing sags and runs at this link - http://www.finishwiz.com/runsag.htm
http://www.finishwiz.com
I've been moving around between different products (although mostly from the ML Campbell Co. - either the Duravar or the Dull-15 precatalyzed. Incidentally, any suggestions on a durable product that has a real satin finish and goes with an open-pore look?). Not sure of the size tip (a mid level I would think). I use HVLP (Fuji) with a non-bleeder gun.
I think I'm basically laying it on too thick and need to move the hand a bit faster, thin a tad less, and take someone's advice of releasing a bit earlier in the corners. I try to hold the gun about 6 inches off the surface, but maybe I will try backing that off a touch as well...
PF, you have answered some of your own questions. Backing away from the piece to find the optimum spot for the fan spray from your gun would probably be your best advice. Less fluid maybe, air control is important. I would try minimizing all the settings and then spraying on cardboard to see what the effect is. This constitutes practice and is easily transferable to your real piece. In short, 6 inches is usually too close. aloha, mike
Paul ... Thanks for the link on fixing runs and sags. Happy new year
Brian
Happy New Year Brian. :)Paul
http://www.finishwiz.com
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