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Problems spraying primer

Discussion in 'The Hokey Ass Message Board' started by Tcoupe, Jul 27, 2009.

  1. Tcoupe
    Joined: Nov 14, 2003
    Posts: 314


    Trying my hand at polyester primer again because I have heard people go on and on about how amazing it is. Well I can't get the shit to spray right at all. At first I used a cheap gravity feed conventional gun with a 2.0 tip, it would spray ok but I had to hold the gun real close to the 2 inches away and then I had to travel real slow, even then it left a lot of orange peel. I could turn the fan down to almost zero and spray but thats just not a very good way to do it. After trying other options like thinning and adjusting the gun every which way. I opted to buy a new gun...a HVLP gravity feed with a 2.5 tip. Its not the most expensive gun ever, but it seems like a good one. Now I just tried it out with some slick sand, same would'nt spray at all unless I turned the fan down all the way, then it was like a hose. I tried adjusting the fluid tip and the air pressure till I was blue in the face and got no results. There are two air regulators one at the bottom of the handle and one right where the air line connects. I can thin the stuff down like milk and get a good even spray but that defeats the purpose of the slick sand I think.

    One more thing, I noticed on the new HVLP gun is the paint in the cup bubbles when I pull the trigger, not a whole lot just kinda blurps every once in a while.

    I have painted before, 2k primers, metallic base coats and clears...I got good results from these so I am thinking that there has to be a simple explanation for this.

    What are your thoughts on this, the max air pressure at the air cap is exactly
    do you know what psi you have at the cap? Is this stuff just too thick? Will I just need to spray more coats if I do thin it to get a good build?
  2. You have enough volume of air? What size and how much hose? A good moisture trap and filter? Are they clean? Is the cup vent pluged? Can be a lot of reasons for whats happening. What tip size does the material call for? Are you shure the mix and reducer is right? Cap and tip clean?
  3. Tcoupe
    Joined: Nov 14, 2003
    Posts: 314


    Compressor is rated 7cfm at 40psi and gun calls for 4.2 - 7.1cfm with 29 psi recommended.

    3/8 hose 25ft long just changed all of my air fittings over to bigger high flow fittings.

    I have two moisture traps, one mounted on the wall between compressor and line leading to hook up on wall and one on hose where it connects to wall. Also have disposable moisture filter on gun. Yes clean and emptied often.

    Cup vent is not plugged.

    Slick sand calls for 1.7-2.4 I tried 1.7, 2.0 and finally 2.5.

    The slick sand does not have a reducer...its mixed with a catalyst. It can be thinned with acetone though.

    Hope this helps...anything else anyone can think of?
  4. philly the greek
    Joined: Feb 15, 2009
    Posts: 1,862

    philly the greek
    from so . cal.

    I would reduce it down til it sprays on wet , and put on multiple coats to build up the mil thickness. Just a thought.

  5. Abomb
    Joined: Oct 14, 2006
    Posts: 1,659


    I think it's probably too thick to properly atomize....First I'd try upping the pressure, I can never get the volume or flow I like at the manufacturer's recommended pressure, if that doesn't work, your reduced to reducing ..........
  6. David Totten
    Joined: Nov 21, 2005
    Posts: 248

    David Totten

    A 2.5 tip should spray polyester with no problem . Do you have the trigger control screwed out ? If so thin with acetone until it sprays and flows like paint. Some orange peel is normal with polyester.
  7. skullhat
    Joined: May 30, 2009
    Posts: 892


    i would agree with what the guys have been postin, and would add to double check the fluid nozzle, as bubling in the pot is usually caused by a clogged tip or air cap

  8. chopolds
    Joined: Oct 22, 2001
    Posts: 5,879

    from howell, nj
    1. Kustom Painters

    Also check that the nozzle is tightened up. That will cause bubbling in the cup. If the gun is new, take it apart and check it for any things that might keep the nozzle from seating (burrs, chips of metal, even deep scratchs). Especially common in the cheaper spray guns.
  9. pimpin paint
    Joined: May 31, 2005
    Posts: 4,937

    pimpin paint
    from so cal


    This does sound, as Chopolds pointed out , as an internal gun problem.
    But I've another question, is there a gage at the gun body, and what does it read? The gage at the air transformer could be a liar! How does the gun shoot straight thinner, with a wet, well formed pattern?


    Always cover the cap/needle with a rag when attempting this! Failure to do so may result in paint under pressure being injected into your skin and into the bloodstream resulting in blood poisoning! A late painter friend of mine "Jimmy the Greek" ,only had nine diggets on his hands. When I asked how he lost the one finger he said "cleaning a spray gun under pressure"

    Swankey Devils C.C.
    "Spending A Nation Into Generational Debt Is Not An Act Of Comapssion!"
  10. ken1939
    Joined: Jul 5, 2008
    Posts: 1,558


    I had issues with this too. It depended for me on temps and humidity. Most of the time, I would mix the catalyst for the Slick Sand ( really do like that brand though) and ad "some" ascetone not alot. Just to keep the pot life longer.

    I tended to have it cure faster than I wanted. Mainly during spraying. I would get more runs than orange peel. Pressure and needle size is important. Wetsanded with 320. Not fun, but the outcome was well worth it.

    I then topped that off with 5 Star Hotrod Primer.
  11. Slag Kustom
    Joined: May 10, 2004
    Posts: 4,312

    Slag Kustom

    if there is a little bubbles in the cup it could be a vent issue and the culp is gulping air from the fluid tip
  12. D-fens
    Joined: Aug 30, 2007
    Posts: 369

    from Huntsville

    Like everybody else says. Thin it just enough where it'll spray and rock it.

    Some guns just don't seem to like filler primers. I use PPG K36 mixed as filler primer sometimes, and my good Devilbiss gun won't spray it. Picked up a cheap HF "primer" gun and it does fine with a 2.0 tip.
  13. plodge55aqua
    Joined: Jan 4, 2009
    Posts: 1,710

    from Alberta

    make sure your vent on the cap is clear..
  14. SlowandLow63
    Joined: Sep 18, 2004
    Posts: 5,953

    from Central NJ

    Thats good advice and something I never even thought of. Thank you.
  15. Rio Grande Valley Deuce
    Joined: Jul 10, 2005
    Posts: 529

    Rio Grande Valley Deuce


    I'm not an expert painter, but I've applied a lot of primer with an inexpensive, but new spray guns using about 20 psi. I've usually filled the paint gun with about 75% primer and 25% thinner (or recommended thinning fluid and %). My experience has been that the primer is ready to apply when the mixture is at about a milky consistency. The paint gun will need to be adjusted to apply it to your preference, thin or thick. We've usually spray it about 8 to 10 inches away from the metal.

    Hope this helps
  16. gotwood
    Joined: Apr 6, 2007
    Posts: 264

    from NYC

    Load the gun with acetone and see if she sprays? If so you are probably good at the gun. Problem with ploy high build primers is you have to disassemble and clean the gun after each use. It will harden in the gun. Another problem is it setting up as you are spraying and clogging tip.

    Clean gun thoroughly if it sprays acetone. Load it up with a bit or primer no hardener. See if it sprays. You really have to pull out the screw with some set ups so let if come out heavy as you are only testing. If you can't get a heavy spray pattern you probably have a pressure problem.

    Be careful thinning as it kind of kills the idea of using a high build surfacer and also can cause problems if you do not give enough time between coats.

    I am going with hardener problem but check in order otherwise you are just guessing and throwing away paint. By the way my cheap 2.0 off shore Sata copy works better than my Sata real deal.
    Joined: Nov 17, 2007
    Posts: 381


    i kinda had the same problem,but i sprayed once and it was so so,i ended up turning up the pressure and reducing a little and it worked ok.. im using a 2.0 tip also
  18. hotflint
    Joined: May 9, 2009
    Posts: 310


  19. mikhett
    Joined: Jan 22, 2005
    Posts: 1,412

    from jackson nj

    Make sure you discard the little screen filter in the cup that comes with most gf guns. Throw it in the trash and strain your paint. I always reduce poly with acetone till it sprays wet. I usually use 40 psi at the gun with a astro 2.o hvlp primer gun. Dont worry about the 10 psi at the tip.
    reagen likes this.
  20. SlowandLow63
    Joined: Sep 18, 2004
    Posts: 5,953

    from Central NJ

    Another good point. I leave them out for everything except for clear and single stage. I still think the problem is in the gun if he's getting bubbles in the cup, but having the filter in there could result in a crappy spray pattern.
  21. Tcoupe
    Joined: Nov 14, 2003
    Posts: 314


    I flushed the gun with straight acetone when I first got it because it had some yellow gummed up stuff inside it and assembly lube on the needle. After I got it cleaned it sprayed the acetone great, the fan would go from about 10 inchs down to about an inch pattern. I did take out the little filter before spraying the primer so that one is out. Im going to try to thin it down as suggested and see what will happen. Thanks guys.

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