Spray-Gun Technique to Prevent Orange-Peel

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Spanish The right pressure settings should do the trick. March 18, 2005

Question
I'm at my wits end. I get orange peel with every setting, and every type of finsh applied. I've gone from a 94 air nozzle to a 91, high pressure to low pressure and thinning my lacquer, polyurethane, varnish, to not thinning. Is there anyone who is getting great results using the Binks

Forum Responses
(Finishing Forum)
From contributor R:
I have used Binks Mach 1 for years without trouble. Have you tried a retarder instead of thinning? Orange peel is usually from drying to fast.


From contributor G:
Binks Mach 1 SL is a great gun. What product are you spraying and what are you thinning with? What viscosity are you spraying at? What are your pot pressure settings? Try your viscosity about 25 sec Ford #4 (20 sec Zahn #2) with about 10 lb fluid and 40 lb air with the gun feed flow about 1 full turn open and experiment from there. That should get you in the.

From contributor A:
My Binks Mach 1 became a super gun when I installed the special kit that regulates the air pressure that pressurizes the quart cup. Assuming you're using a quart cup, the kit allows you to dial in the pressure on the inside of the cup independently of the atomization pressure. Cup pressure should be a fraction of atomization pressure, but is usually the same. This can lead to overspray and orange peel.

Don't count on your Binks distributor to know about this. Mine didn't, so I went to the Binks website and found the parts. When I gave him the part numbers, he ordered the kit and it was easy to install. It makes the gun a little heavier, but not so much as to make you want to remove it.



From the original questioner:
I'll check out the Binks site for the kit and give that a try. I don't think that the gauge that is below the handle gives you the info that you really need though.

From contributor B:
If you’re getting orange peel after all you've done then I would check your gun to see if the air vent is blocked.

From Paul Snyder, forum technical advisor:
Start by making sure the viscosity of the finish is right for the needle/nozzle/air-cap you have on the gun. If the finish is too thick, it won't atomize well. Use a viscosity cup to measure the finish and thin as needed. Here's a description of using a viscosity cup - Measuring Viscosity.

Then make sure the gun is atomizing the finish well. The finish should break up into tiny droplets when you have the settings right. If the finish isn't atomized well, the spray pattern will look more like the picture below on the left. Good atomization looks like the picture on the right.

Left Side


Click here for full size image

Right Side


Click here for full size image

If you're still getting orange peel once you have the gun atomizing well, make sure you're keeping the spray gun the proper distance from the surface and moving at the right speed to maintain an even wet coat that's not too thin or thick (wet mils). If you're still getting orange peel, then adding retarder should take care of it. There are some tips to eliminate orange peel at this link - Eliminating Orange Peel.

http://www.furniturefinishwizard.com/orangepeel.htm

When everything is working right, the sprayed surface should look almost like glass when it's wet.




From the original questioner:
I'm thinking that my problem is that I just don't understand how to set up the air pressure. What do you recommend the pressure at the air compressor should be? I have one of those small knob controlled regulators at the base of my gun. What do you recommend I set that to? I realize that the settings are different for different liquids, but I need a starting point.

From Paul Snyder, forum technical advisor:
After thinning your finish to the proper viscosity, try this to get started;

* Open the cheater valve at the bottom of the gun handle all the way and leave it there.

* Set the air pressure to the gun at 35-40 PSI.

* Spray a few test shots and adjust the fan width to about 7" wide at 7" - 8" from the nozzle.

* Spray some test spray passes on cardboard, craft paper, or scrap boards and adjust the fluid flow until it atomizes well. If you're getting large droplets, turn the fluid down.

* Now turn the atomization air down to the lowest setting that still gives you good atomization with minimal overspray.

If you use a wider fan pattern, you'll need more fluid and more air pressure.

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