Converting a Pressure Pot to Liquid-Flow Application

      Can a pressure pot be adapted to apply stain as a flowing liquid, not a spray? October 14, 2010

I have a permanent, production situation where I need a continuous stain application. We can't use our lineal spray system for several reasons. So I'm wondering if I can take a dual regulated pressure pot and get the pressure low enough so it's almost a gravity drip type with no overspray. It only has to be applied to the part, then the stain would be spread with hand pad applicators.

Forum Responses
(Finishing Forum)
From contributor L:
I'm not sure why you'd need to lower the pressure, but stain can be applied from a pressure pot. Only thing - you'd do better with a pot with an agitator so the heavier components of the stain won't settle out, causing color variations.

From the original questioner:
I do have experience with pressure pots, just haven't owned one in a few years. I'm mainly wondering if I can get it to simply run out without really spraying.

From contributor L:
Let it spray - you'll get better and faster coverage.

From contributor R:
Just turn off the atomizing air.

From the original questioner:
I can not spray this. I am quite versed in all types of finishing, as I have sprayed millions of lineal feet of various products and all sorts of millwork for 25 years. I am simply asking a mechanical question about pressure pots. I will not reveal the particulars of this application, other than this product and process has to be wiped in. I am looking for some way to get the stain on the part without spraying - just hoping to save the time of dipping a pad or roller so frequently.

From contributor R:
Somewhere in those millions of gallons you must have realized there are 2 controls on a professional pressure pot. One is for fluid pressure, one is for atomizing air. By turning off the atomizing air, you get a stream of whatever magical fluid you are using and then I guess you will have to figure out the rest yourself.

From contributor J:
It depends on the viscosity of your stain, but I would think you will need to regulate the air twice. Regulate your main line down to the upper limit of the low pressure regulator, then dial in the low pressure regulator to get the flow you need. If you can not atomize the product at all, you could use some type of custom made nozzle that makes sort of a curtain that you can run your material under. If you do plan on using some atomizing air, regulate it separately from a T at your main line and again in two stages.

From contributor M:
You could use the pressure pot to continuously add stain into the application pad, dispensing with the gun or curtain coating step altogether.

From contributor E:
Contributor R has it right on. No spray, turn off the atomizing air and it will come out like a nice little stream. Seems to me it would be a lot faster to just dunk a pad into the can of stain than to spray a thin line that needs to be spread around.

Here is how I stain. Turn atomizing air down really low so it is sort of sputtering out of the gun in the fan pattern. I spray the work piece like this. I then use a stain soaked rag to spread and wipe down the door. The rag stays wet simply from spreading the sprayed stain around, so no need to go back to the can. I then switch to some clean dry rags to remove the excess stain.

From the original questioner:
Thanks. That is how we normally stain also. This application has to be done differently and rubbed in rather than wiped off. I'm going to see about plumbing the stain directly into a wiping pad with some sort of an on off valve.

From contributor E:
What I do does rub the stain in. You just spatter it all over the wood with the gun, then rub it in with a soaked rag. The rag stays soaked as it rubs the spatter in. Then you use the clean rags to wipe up the excess.

From contributor J:
I think contributor M and the questioner have a great idea. It is obviously something that has to be more thoroughly worked into the wood than a regular wiping stain. In this case a pressure fed felt pad or something like that could be awesome, as long as the pieces you are staining do not have a lot of complex profiles.

From contributor R:
When I wanted to wipe the stain on the automated Makor finish line, we sprayed the stain on through the guns and removed the last gun, replacing it with a brush which pushed the stain into all the profiles, and then just hand wiped the stain off as it went into the stacker. This was for running trim. I don't know if that will work in your situation or not.

From contributor K:
It sounds like you don't even really need a standard spray gun. Something akin to an air blow nozzle might work well. Many of them have a brass end that can be unscrewed and replaced with a fitting. The fitting would hold a short copper tube, which could be "adjusted" (read "smashed") to limit fluid flow. You could add a valve before the gun to further regulate flow.

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