Clumpy spray with siphon gun
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    Default Clumpy spray with siphon gun

    Just putting the first coat of rustoleum 7400 primer on my bridgeport mill. It is coming out clumpy. I am using a siphon gun that was given to me. I do not have any experience with a spray gun. Any suggestions on what I am doing wrong?

    Sent from my SM-G900V using Tapatalk

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    Could be one of several things,

    Paint is too thick, not enough reducer/thinner
    Too much air pressure at the tip
    Too far away from the surface
    Too much fan pattern pressure
    Not enough overlap

    If I was a rookie with an ol' school spray rig, I'd probably practice a bit on some sheet goods, ie: scrap metal, busted up doors or fenders from car wrecks, cardboard, whatever you can find free or cheap. You need to get some skills to do the job to get the results you're looking for.

    Oh, and please don't overlook the minimum breathing protection required

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    Ok I will look for some items to practice on. Can I scuff up the primer on the bridgeport and reprimer? Or do I need to take it back down to metal? It is pretty chalky.

    Sent from my SM-G900V using Tapatalk

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    To get the results you're looking for, I would recommend getting the surface back to smooth again. Try wiping it off with paint thinner, then sand with 80 or 120 grit to finish it. Don't over worry about removing all the primer, just focus on smooth.

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    Did you strain the paint? That is critical to getting a smooth finish. Paint stores sell strainers, but you can make a finer mesh strainer from silk screen cloth as it is available in 400-600 thread per inch.

    The critical thing spraying is not to spray too much, keep the gun perpendicular to the work surface at the same distance.

    When I put polyurethane on my "fine work" bench top made from cabinet grade plywood with a lip to keep small parts from falling off I shot around 5 coats. The thin coats dry quickly. It came out beautifully despite being my first attempt at air spraying. I had previously done a lot of airless, but was not about to put polyurethane in an airless sprayer.

    Another advantage to thin coats which dry quickly is there is less risk of dust adhering to the paint. Pick up a book on auto body painting or go by a shop and take a couple of the guys to lunch. they'll set you straight.

    Reg

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    What are you using for a reducer. You say the paint is 'chalky' which to me would mean very very dry, not tacky or gooey. If it really is a dry chalky condition it means it was cooked with a very hot reducer..too hot, like lacquer thinner. It dried almost on contact and had zero chance to flow out and gloss.

    Stuart

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    Quote Originally Posted by rhb View Post
    Did you strain the paint? That is critical to getting a smooth finish. Paint stores sell strainers, but you can make a finer mesh strainer from silk screen cloth as it is available in 400-600 thread per inch.

    The critical thing spraying is not to spray too much, keep the gun perpendicular to the work surface at the same distance.

    When I put polyurethane on my "fine work" bench top made from cabinet grade plywood with a lip to keep small parts from falling off I shot around 5 coats. The thin coats dry quickly. It came out beautifully despite being my first attempt at air spraying. I had previously done a lot of airless, but was not about to put polyurethane in an airless sprayer.

    Another advantage to thin coats which dry quickly is there is less risk of dust adhering to the paint. Pick up a book on auto body painting or go by a shop and take a couple of the guys to lunch. they'll set you straight.

    Reg
    No I did not strain it. I just bought some strainers today at harbor freight before I read your post. I just bought the 60 to 70 mesh strainers, will that be good enough?

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    Quote Originally Posted by atomarc View Post
    What are you using for a reducer. You say the paint is 'chalky' which to me would mean very very dry, not tacky or gooey. If it really is a dry chalky condition it means it was cooked with a very hot reducer..too hot, like lacquer thinner. It dried almost on contact and had zero chance to flow out and gloss.

    Stuart

    I used acetone which is what rustoleum suggests. Maybe I didn't have the right mixture. It was a pretty warm day too, I don't know if that matters.

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    The Acetone certainly would evaporate pronto, especially on a warm day. If you're going to try this again, don't use Acetone, use a synthetic reducer, or if it's a real warm day, use regular 'paint thinner'. Both those reducers are available at your neighborhood ACE hardware. The synthetic reducer is called 'painters solvent' while the paint thinner is labeled...paint thinner.

    The items listed above are just part of the equation. The other concerns are how thick or thin you mix the paint and the settings on your spray gun. I'd check out YouTube for a beginners video on spray painting.

    Stuart

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    It looks super dry from the pics. You want to be getting primer on pretty wet in this situation. Can strain primer with a corse strainer, practise on carboard/masking paper taped to the wall. Make sure your gun has a big enough setup as you'll need it with syphon, gravity gun much nicer to use. Plenty on youtube. This guy's pretty good YouTube
    Check acetone as a reducer, that really doesn't sound right.

    Happy spraying

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    Quote Originally Posted by atomarc View Post
    The Acetone certainly would evaporate pronto, especially on a warm day. If you're going to try this again, don't use Acetone, use a synthetic reducer, or if it's a real warm day, use regular 'paint thinner'. Both those reducers are available at your neighborhood ACE hardware. The synthetic reducer is called 'painters solvent' while the paint thinner is labeled...paint thinner.

    The items listed above are just part of the equation. The other concerns are how thick or thin you mix the paint and the settings on your spray gun. I'd check out YouTube for a beginners video on spray painting.

    Stuart
    I watched quite a few videos, not too many on the siphon style gun. I have read that sometimes rustoleum takes a long time to dry. The rustoleum representative told me acetone should be used to thin before I bought the paint, but I thought it would help it dry faster to. Thanks for the suggestions.

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    Quote Originally Posted by Demon73 View Post
    It looks super dry from the pics. You want to be getting primer on pretty wet in this situation. Can strain primer with a corse strainer, practise on carboard/masking paper taped to the wall. Make sure your gun has a big enough setup as you'll need it with syphon, gravity gun much nicer to use. Plenty on youtube. This guy's pretty good YouTube
    Check acetone as a reducer, that really doesn't sound right.

    Happy spraying
    I have a 10hp, 120 gallon compressor that goes through a filter and desiccant system. The Rustoleum representative told me acetone was the same as their thinner that was recommended. Thanks for the link. Any suggestions on a gravity gun?

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    I have used a Binks #7 for a mazillion years and it works perfectly, and like any spray gun, siphon or gravity, you need to know how to use it..and how to use the material you're spraying..and how to prep the item to be sprayed.

    An enamel like Rustoleum isn't made to dry fast, and when you use a hot reducer like Acetone or lacquer thinner, it won't allow the paint to flow out and will kill its gloss. I have painted quite a bit using Rustoleum products and the recipe always includes a hardener and some Marson Smoothie. The paint dries fast and hard and stays glossy.

    HVLP (gravity) guns are all over the place and cheap too, but you still need to know how to use one..they're probably more fussy to use than a good old siphon gun.

    That's been my experience.

    Stuart

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    I agree with what atomarc (Stuart) is saying about drying to fast because of to fast a thinner.
    If you want to try the thinner you have hold the gun a little closer to the part and move slower to put a thicker layer of paint, which will take longer than 1/2 a second to dry. Also dont paint it when it is hot outside, paint earlier in the morning so the heat is not helping the fast drying paint dry faster.
    Try it on a part that is easy to wipe off, if it works keep going, if not then you have to get slower thinner.

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    I should have mentioned that the paint is partially drying in the air on its way to the part being painted. That is why slower thinner and/or cooler temps will help you. It needs to be wet when it gets to the part.

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    Acetone is going to flash dry, I would suggest plain paint thinner with a dash of Penetrol. Always test and set your gun before shooting the item you want to paint, as mentioned above even a plain piece of cardboard will suffice. And wear a respirator!

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    Thanks for all the suggestions. I will give you an update when I try them out.

    Sent from my SM-G900V using Tapatalk

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    I thinned the primer with paint thinner this time, 15%. It looked good to me on the cardboard. Then started painting and it did the same thing on the mill. The siphon gun I think has a 1.4 tip. If you thin primer/paint too much what will it do? The primer seems thin to me already, but I've only rolled paint on houses.

    Sent from my SM-G900V using Tapatalk

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    I forgot to add a picture of where I was trying to build it up more and slowed down my movement and was very close. It looked a lot better but seemed like I was too close, on the verge of running.

    Sent from my SM-G900V using Tapatalk

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    That looks better in the pic. That is more like what you want to see, paint that got on wet and flowed a bit. For your dry spray problem the amount of thinner is not as important as the speed in which it dries - more thinner will just make it run. Leave the can open for a while if you got to much thinner in it, stir often to keep a skin from forming on top.
    Just keep the gun close, adjust it for more paint volume if you can, and also adjust the fan so it is wide. Dont worry about getting runs, they will sand out very easy and you need to know at what point it will run so you can correct for it with faster travel, farther away or adjust gun volume for less paint.


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