Air-Assisted Airless: Advice for a New User

Tip choice, spray technique, and equipment care and maintenance advice for a finisher who has just purchased his first AAA setup. February 17, 2014

I bit the bullet and ordered a Cat AAA system, which should be here later this week. I've been using a demo pump for the last couple days and have some questions.

First, I've been using a 411 tip on the Cougar gun spraying Resistant thinned about 10-15% and am getting a great finish on doors. However, beaded face frames are proving a bit of a challenge. How do the different tip sizes affect the spray? I know I can get a wider/narrower fan, but does it also change the amount of fluid coming out?

Second, when I spray the doors they look terrible! Like someone blew a handful of dust on them while I was spraying. After they flash off for several minutes they clean up and once fully dry they look fine! Is this normal?

Lastly, do you guys generally use separate fluid hoses for pigmented and clear coats? This kit is pushing the budget as is right now, not to mention I don't really shoot all that much material so am not going to be adding a separate pump anytime soon. But am a little worried about whether or not I'll get contamination once I run pigmented finish through.

I do plan on asking the rep about this stuff as well when my kit comes in. I just want to have as much info as possible so I'm not starting from scratch.

Forum Responses
(Finishing Forum)
From contributor D:
What type of problems are you getting from the beaded face frames vs. non beaded? Also, why on earth are you still spraying Resistant, instead of changing over to Stealth? Are you following reduction to achieve proper viscosity first, and then setting your fluid and air pressures? has more than enough literature to answer your questions about gun/tip/ setup/material viscosity/approximate sq. footage/product pricing calculator (for extra hoses) and cleaning kits. Since you are using a loaner, I'm assuming it's through your MLC rep? I would get with him/her and work on spray technique using the different tips, ideally a .409 but make sure the pre-atomizing spacer is removed from the tip (your distributor will most likely send you a .409f and it will have the h2o spacer in it).

From contributor L:
Doesn't matter what it looks like wet. How it looks and feels when dry is all that counts. Resistant through a AAA pump can be a challenge at times. The shearing of the pump can introduce bubbles which lead to a bumpy finish. If you aren't getting this then don't worry about it.

I use Stealth and I thin it about 15%. They say to do 30% but I have no luck with that.

From contributor J:
I use a 511 tip for almost everything. Primers, CV, pigmented topcoats, waterborne. Everything. I prefer the really wide fan for covering parts like big panels and big doors faster. Primers and pigmented I thin about 10%, no thinner on clears. This of course would be different based on the products you use. As mentioned, look at Stealth. It's a better product. You will find the odd product that doesn't like going through a pump because of the shearing of the fluid that can occur.

Tip size, 1st number is the angle - 5, which will spray a 10" wide pattern. A 4 will spray an 8" pattern, etc. Second number is the orifice size. 11 is 0.0011".

So if you keep the orifice size the same and change the angle to a larger fan, the same amount of material will come out of the tip, but spread over a slightly larger area in turn making the coating thickness slightly thinner. Very slight. This assumes every other variable remains constant. So if you slow your hand down, you could then put a thicker coat on.

Hope that makes sense. I use a single hose. I also make sure to flush and clean it out very well after every use. I leave it full of thinner and under pressure when not in use. I can't remember ever getting a white spec on another job. And as contributor L says, it's the dry film that needs to look pretty, not the wet film.

From the original questioner:
Thanks guys. I'm having a tough time getting the right amount of finish with the beaded face frames. As I've only had the pump for a couple days I haven't tried normal face frames yet, so can't compare. It's probably just a matter of getting used to the gun, but getting enough finish on the inside of the frames without putting too much on the beads has been hit-or-miss. The worst is with the wrap around face frames - like upper wall cabinets with a side panel. I've done one twice and still can't get the right amount of finish on - too many sags! I'm sure I'll get the hang of it but was just wondering if anyone else ran into this when switching from a painfully slow turbine to AAA?

As far as Stealth, I haven't tried it yet. I'll have to ask the rep about it next time I talk to him. Then again non-biased info is good to have also! I've been using Resistant for years and haven't had any problems so what is Stealth going to offer over Resistant?

I'll check out the site later also. I just like to get firsthand info from guys using this stuff in real world. Numbers are great when you understand them, but sometimes it's better to have someone with experience say "start out with these 2 tips sizes and go from there." I think I'm going to start with the 409 and 411, unless anyone has other suggestions?

It's good to hear guys are shooting both clear and pigment with a single hose. I think I'll try that for a while and if I run into problems I can always change over later!

From contributor J:
I would suggest a 409 and a 511. 409 will be better for small parts - like the face frames - as you will have a narrower pattern and a slightly thinner wet film. 511 will be better for large (8" wide and bigger) parts. The wider pattern and larger orifice will let you really move fast. I find I use the 511 for almost everything.

Go to ebay and order an ultrasonic jewelry cleaner. Get one with a metal inside bit so you can use thinners or whatever in it. You can get them for about $25 shipped from china. This is absolutely the easiest and fastest way to clean a tip.

You will also want a set of tip broaches. Every once in a while, a particle will clog the orifice and you need the broaches to clean it out. Should cost about $20 for a 10 pack. They are reusable, so a 10 pack will last a long time. I think it's been about 2 years since I ordered them last.

When done spraying, even if stopping for 20 minutes, store your tips and aircap in a baby food jar full of thinner and use a thinner soaked rag to wipe the tip of the gun clean. Make sure you stay on top of the throat lube, and keep the piston above it clean. When done spraying for the day, make sure you store the pump with the piston in the down position. This is to help prevent getting a stuck ball. Get a stuck ball and your $100 for a pump rebuild kit.

When storing for the day, I leave the lines full of thinner and under pressure. This helps prevent a film from forming on the inside of the fluid hose. To clean at the end of the day, purge lines of finish. Use a dirty thinner to flush out finish residue, then use virgin thinner to flush out the dirty thinner. So 3 pails. Waste, dirty thinner, virgin thinner.

Purge the dirty thinner into the waste. Then purge the virgin thinner into the dirty thinner for a little bit, then continue to purge the virgin thinner into itself. Next day, purge the virgin thinner back into the virgin thinner pail, and prime the lines with finish and you're good to go.

Following this regimen, I was 4 years until I needed to rebuild my pump.