Cleaning an Air-Assisted Airless after^ Using Pigmented Products

If you use the same AAA gun for applying pigmented as well as clear finishes, you should practice careful cleaning. April 19, 2011

My pride and joy is my Kremlin AAA. So far I have only used it for clear finishes and now have some projects come up using white and gray pigmented finishes. I produced the samples with my old cup gun and was reminded how well the Kremlin really does work. With 25' of hose, will I be weeping and gnashing my teeth trying to get it clean for clear coats if I pump pigmented products through it? I use MLC Magnamax.

Forum Responses
(Finishing Forum)
From contributor R:
You have to clean your hoses very thoroughly. Lacquer or acetone. Or, do like I did, and invest in another set of fluid and air hoses dedicated to pigmented coatings. But you still have to run a least a gallon of cleaner through the pump.

From contributor L:
First pigmented job I did, I had white specks showing in my clears for quite a while after. I would send my pigmented jobs out for shooting.

I invested in another fluid line and some end caps for the other non in use line. When I put a line in storage, I run some dirty thinner through it first and get most of the pigments out of the line, and then clear the line from liquid by pulling the siphon tube out of the material. Then pour a new bunch of thinner in a new cup and pump it through the Kremlin into the used thinner cup. When it turns clear, I cycle it in the new cup for a few minutes and then pull the lines off the gun and pump and cap them, trapping the fresh thinner in the line.

When switching over, I will run fresh thinner through the line and clean the screen at the gun. I do this until no more particles show up in the filter, usually about the third time. Then you are good to go. This works for both the clear and pigmented lines.

From contributor H:

I would buy another hose for about 70 bucks. Save time, money, and sleepless nights. Take the lower part of the pump apart and check the lower ball check. Should take you less than 30 minutes to inspect it.

From Paul Snyder, forum technical advisor:
I switch back and forth between pigmented and clear solvent finishes all the time and have never had a problem. I just run some lacquer thinner through the pump between coatings.

From contributor M:
I also swap back and forth between clear and pigmented finishes without any problems. My only advice is to flush the system with a hot/fast lacquer thinner (not temperature). One that flashes fast - it's usually the cheap stuff. To me it seems to clean faster then a standard or slow drying thinner.

From contributor G:
I have had problems cleaning my Kremlin 10:14 pump after using Clawlock primer. Every time I need to pull the pump apart and clean the upper and lower pump ball. This is after running first the dirty thinner and then clean thinner. I also need to clean the gun screen every time. I have gone back to my pressure pot system for the primer, but use the Kremlin for the pigmented topcoat with no problems (MLC Resistant).

From the original questioner:
Thanks for all the input. I also spoke with my Kremlin rep today. His suggestion:

1. Do a quick clean to get the lion's share of pigmented product out.
2. Clean the gun filter.
3. Dial back the fluid pressure a bit (still enough pressure there so the pump cycles smoothly).
4. Secure the gun so it dispenses back into the solvent container you're pulling from, clamp or wire the trigger so it's on, and let the thing cycle for an hour or two.
5. Check the gun filters again and repeat if needed, or if you really feel like it, open up the lower portion of the pump, physically clean it, reassemble and you're good to go.

Another thing that's nice is each piece will get clearcoated, as I'll need to lock down a glaze, so if I get a tiny bit of fleck, it won't be the end of the world. So between Kremlin and everyone here with boots on the ground, I'll give it a go. I think I'll try one color, see how it goes, and then see if I want to go through it with the second project. Thanks!

From contributor N:
We used to switch hoses, but as a couple of posters and your rep said, just take the tip out and let the pump cycle slowly for a while. I really doubt you'll have any problem.

From contributor E:
I agree with both the one set people and the two set people. You can use one set of hoses and more thinner cycled during the clean or use two sets and less thinner.

On big jobs I tend to be less patient with the cleaning when I'm in a hurry to go from clear to white, so I use two sets of hoses. Like contributor L, I trap clean thinner in a hose when I hang it up for storage to keep it wet.