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Thread: Newbie: Some Basic Questions

  1. #1
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    Default Newbie: Some Basic Questions

    Hello! Lots of questions here, but if anyone can help with any of them, I'd be grateful!

    Background:
    I've never painted before but would like to paint my '72 Corvette (which I am custom-building ground-up) in the garage. I plan on bright red polyurethane bc/cc.

    Compressor: Old Sanborn purchased from a friend; he said it does 18cfm@100psi, 80 gal. tank, 5 hp. He said it supported two painters at once in his shop years back (what kind of guns...?). From the little bit of research I've done on compressors, the numbers this thing puts out seem very high for just 5 hp.

    I am a perfectionist and (with some practise) want the job to look very professional/top-notch. While I am certainly not looking to blow money on a gun with bells and whistles only the experienced can appreciate, I am also not opposed to paying more if it means more user-friendliness or a higher chance of achieving an excellent job.

    Questions:
    Do my compressor specs sound realistic for only 5 hp?
    Will my compressor limit me to a certain type of gun?

    Knowing I will be very slow and cautious, will this affect what gun I buy, or just what settings/tips I use? I've heard some guns lay the paint down too "fast": is this just a result of the tip sized used, such that the same gun could be "slowed down" with a different tip?

    Can one gun do everything: primer, bc, cc, just by swapping out tip sizes? Why do I read of people using a dedicated primer gun?

    Is it true the "compliant" guns are the best of both worlds, conventional and LVLP? Should I only consider a compliant gun, or would a good HVLP or LVLP do the trick? Which type would minimize the overspray cloud?

    Thank you!
    Patricia Brown

  2. #2
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    Default Answers...

    Questions:
    Do my compressor specs sound realistic for only 5 hp?
    Will my compressor limit me to a certain type of gun?
    Yes that sounds right for 5 hp and you should be able to use any type of automotive-type spray gun you want.

    Knowing I will be very slow and cautious, will this affect what gun I buy, or just what settings/tips I use? I've heard some guns lay the paint down too "fast": is this just a result of the tip sized used, such that the same gun could be "slowed down" with a different tip?
    Some guns are faster than others while others may be easier to control. I don't recommend trying to slow things down by changing tips. The tip size is usually determined by the viscosity of the materials you're spraying.

    Can one gun do everything: primer, bc, cc, just by swapping out tip sizes? Why do I read of people using a dedicated primer gun?
    One gun can do it all as long as you take more care to clean out the primer. Primer clings to the guns interior surfaces more than most paint does and you need to be more vigilant in order to remove it properly. If you use a dedicated primer gun it's usually not as critical because a speck or two of primer coming out while shooting more primer is no big deal.

    Is it true the "compliant" guns are the best of both worlds, conventional and LVLP? Should I only consider a compliant gun, or would a good HVLP or LVLP do the trick? Which type would minimize the overspray cloud?
    Compliant guns use a higher air pressure at the air cap which tends to atomize the paint better but also makes the gun a little more difficult for the novice to control than HVLP. HVLP uses lower air pressure but more air volume to atomize the paint (your compressor will still work) and that lower pressure creates less of an air pillow on the surface and thereby generates less overspray and helps make the application of the paint more consistent. While you may get a little more orange peel with HVLP you will almost always need to sand and polish the paint in order to get a really good job so compliant or HVLP makes little difference to the person who only paints occasionally. I'm an advocate for HVLP for most new painters who want the best results when they are in the learning stage.

    There are a couple of excellent HVLP guns on the market so it comes down to how much you want to spend. The DeVilbiss GTI comes with three fluid tips and costs just under $300 and the Dura-Block 007 comes with three separate heads as well as cups, stand and inlet regulator for $479. Dura-Block also makes a less expensive HVLP gun called the 7003GMS which is being offered with two fluid tips until the end of the month, this gun sells for $129.

  3. #3
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    Len, thank you for all the help!

    So when shopping for a gun, how do I know if it would be too fast or not? Or would any HVLP be slow enough for a beginner?

    To clarify: Is it correct that "fast" refers to the gun atomizing the paint so well it flashes off very quickly, thus making it difficult to get around the car before the first part flashes off, causing a yucky finish where it overlaps?

    So if I'm going to try to do it all with one gun, it would be very important to select a gun that comes with multiple tip sizes, as primer, bc, and cc all require different tips?

    Between the $129 Dura-Block and the $479 Dura-Block, what would be the main difference(s)?

    Thank you,
    Patricia Brown

  4. #4
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    Default

    Background:
    I've never painted before but would like to paint my '72 Corvette (which I am custom-building ground-up) in the garage. I plan on bright red polyurethane bc/cc.

    Compressor: Old Sanborn purchased from a friend; he said it does 18cfm@100psi, 80 gal. tank, 5 hp. He said it supported two painters at once in his shop years back (what kind of guns...?). From the little bit of research I've done on compressors, the numbers this thing puts out seem very high for just 5 hp.

    ================================================== =======
    That sounds about right, but your going to need more than just the compressor. You will need a good water trap, high flow connectors a good
    hose and some form of dryer for the air, tyypically the air dryer can come
    as part of the water trap.

    ================================================== =======

    I am a perfectionist and (with some practise) want the job to look very professional/top-notch. While I am certainly not looking to blow money on a gun with bells and whistles only the experienced can appreciate, I am also not opposed to paying more if it means more user-friendliness or a higher chance of achieving an excellent job.

    Questions:
    Do my compressor specs sound realistic for only 5 hp?
    Will my compressor limit me to a certain type of gun?

    ================================================== =======
    That compressor will work fine..
    ================================================== =======

    Knowing I will be very slow and cautious, will this affect what gun I buy, or just what settings/tips I use? I've heard some guns lay the paint down too "fast": is this just a result of the tip sized used, such that the same gun could be "slowed down" with a different tip?

    ================================================== =======
    The speed at which a gun lays down paint depends on the viscosity of the
    paint and also the tip / cap, Look at the gun like a tap. Open the tap more and more will flow out.

    ================================================== =======

    Can one gun do everything: primer, bc, cc, just by swapping out tip sizes? Why do I read of people using a dedicated primer gun?

    ================================================== =======
    One gun can do pretty much everything, but primer can be tricky as it is
    typically thicker in viscosity than standard paint. A typical tip size for primer
    is 1.8mm but for high build epoxy primer this might not be enough. 1.8, 1.4
    will work good if you reduce or thin the primer prior to application.

    People use a dedicated primer gun for various reasons mainly I believe
    they wish to keep their high end gun for just paint. On the flip side a high
    quality gun could be used for primer too, Since your paint is going to be applied on top of primer a higher quality gun might lay the primer flatter
    so hense you would have a better surface to paint on.

    ================================================== =======

    Is it true the "compliant" guns are the best of both worlds, conventional and LVLP? Should I only consider a compliant gun, or would a good HVLP or LVLP do the trick? Which type would minimize the overspray cloud?

    ================================================== =======
    I think the HVLP Stuff is BS, HVLP is just a standard that dictates a 10psi cap pressure on the gun. Regardless if the gun is HVLP or not its pretty easy to up the air pressure and the gun is no longer compliant with the HVLP standard

    I use a Devilbiss GFG670 which is a compliant gun. I would go with something similar to that. If you wish to keep overspray down you can reduce the air pressure into the gun but not to the point of where it cant atomize the paint.

    ================================================== =======

    One other thing. Before you decide to go ahead and paint, learn as much
    as you can. One important factor is the paint viscosity and methods used
    to reduce or thin the paint to a sprayable viscosity. You can have the best
    equipment in the world but if that paint is the wrong viscosity your end result
    will be very poor. You might consider getting a ZAHN 2 cup to check the
    mixed paint viscosity prior to application.

    There is also a video available for purchase on this site, as a beginner it might save you alot of hair pulling if you go ahead and get it.

    What paint do you have in mind ???

    Good Luck on your project.... Thanks X

  5. #5
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    Hi X,

    Thanks for the pointers. Yes, I am aware I will need a good desicant filter for my compressor. I do not yet have one. I am under the impression an in-line, right-at-the-gun, disposable type is acceptable. I would LOVE to be able to use the re-chargeable type (the expensive ones where you can replace the media, rather than throw the whole thing away), but I called Milton Industries (I'm presently using Milton's F-R-L units) and the guy said their rechargeable desicant filter would not function well with only 5 hp compressor. He said I would have to use the little throw-away type at the gun. Maybe there's another brand out there that would work...

    You bring up a good point about a more expensive gun possibly laying the primer down flatter and better, thus making a better base for the paint. Len was saying primer can be a bit hard to clean out of the gun, but if I'm very careful I could be ok running primer and paint through the same gun. I like the idea of spraying the best primer layer I can.

    Yes, I just ordered the video off this site. I have been scraping together any info I can before buying a gun or anything. I have a couple of the Paintucation videos, also, and plenty of books. Typically the books leave me feeling like the whole thing is impossible, but I know it can't be rocket science.

    If you know of any other videos, articles, etc. on painting, please let me know. I'm always keeping my eyes out.

    I don't yet have a particular brand of paint in mind. It has been drummed into my mind to pick a system/brand and stick with it all the way through. Quite frankly, I don't know anything about one brand over another; about all I know is that there are some big names that sound familiar! That will be another whole can of worms to deal with. Actually, I'm probably a year or so out on the actual paint job. I'm building the car and am doing some fiberglass repairs right now. I almost have the firewall spiffed up, and I will need to primer and paint it (black) before too long, as the body will be going back on the chassis relatively soon. But the exterior body paint (red) won't happen 'til the whole car is done. Regardless, I'm beginning to wonder what paint system to pick and gun to use, as I might as well do the firewall with what I'll be doing the rest with.

    Thank you for your help,
    Patricia

  6. #6
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    Default HVLP/Compliant

    If you look at the tip of an HVLP gun and the tip of a compliant gun you'll see that the gap between the fluid tip and the air cap is much larger on the HVLP. This causes the gun to use more CFM at a lower pressure. The pressure can be increased until the gun is no longer HVLP but it can also distort the pattern when the pressure is increased so it's not really BS as x711 indicates, it's engineering. A decent HVLP gun is slower in that the motion of your arm when applying the paint is actually slower and the control is better because you're not chasing the gun around the car and the lower air pressure makes the paint application more consistent; less runs and dry spots. The "compliant" gun will break the paint up into smaller droplets but you will get more of the paint in the air and less on the car than when you use a decent HVLP gun.

    One thing that should be noted is that it's better to buy a decent HVLP than to try to go with an inexpensive HVLP. Stick with HVLP guns that are at least $100 or more. If you can't afford $100 go with a conventional spray gun. A general rule is that the more you spend on a gun the easier it is to use so get the best gun that you can afford.
    Last edited by Len; 01-12-2006 at 10:27 PM.

  7. #7
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    Len,

    HVLP makes sense to me, then, as I definitely want to minimize overspray and "cloud" conditions. I have to do this in my garage, so the less mess the better. I like the idea of slow application, too.

    Yes, I'm expecting to pay well over $100 for a good gun. Of the 3 you mentioned, the DeVilbiss GTI ($300), the Dura-Block 007 ($479), and the 7003GMS ($129), which would yield the best results for a newbie? Would they all handle primer through cc? What's the difference between the two Dura-Blocks, other than lots of $?

    Patricia

  8. #8
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    Default Dura-Block Guns

    The two Dura-Block guns are very different. The 7003GMS is a low end HVLP gun that works well but not nearly as well as the 007. The 007 is like buying three high-end guns for the price of one. Check out the details on the 007 at the link below he picture. The GMS is a low budget gun that produces good results for the money but the 007 is a high-end gun that is very efficient with it's air and paint usage as well as being able to apply an excellent finish using primer, single stage and base/clear.


  9. #9
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    Len, thank you for the info on the guns. Is there an advantage to having multiple heads rather than just tips? It sounds like many guns come with multiple tips, but I haven't heard much about multiple heads. What is the advantage?

    Also, IF I were to flub up and accidentally damage a head by leaving a speck of primer in it, such that it no longer did a great job spraying top coat, can I a replacement head be purchased from Dura-Block?

    On a seperate note, I was at a different site where a few guys were raving over their (cheap) Astro Pneumatic guns, which are apparently copies of other brands' high-end guns. They talked like they were great, especially the LVLP model, EVO4014. They are so cheap there must be some compromise somewhere...do you know anything about these guns?

    Patricia

  10. #10
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    Let me follow up on my earlier statement about thinking HVLP is BS.

    I was referring to the difference between a HVLP gun and a gun which falls
    in the middle ground of conventional and hvlp such as devilbiss gfg670 plus gun.

    When painting it is desirable to atomize the paint correctly, Even when painting slow with a hvlp gun you may find that you have the gun set for its specs but it still is failing to atomize the paint so the paint you paid alot of $$$$ for is going on the panel and turning out not looking too good. Painting clear would be a very good example of this. "In this situation you may opt to up the air pressure in the hope of atomizing the paint better" At this point
    your HVLP Spec goes out the window.

    In the last few years manufacturers such as Sata,Devilbiss etc have shifted away from HVLP and on to what they call Plus guns or higher efficiency guns.
    The reason is this. Atomizing problems with the paint and productivity for the end user"

    These higher efficiency guns can emulate a hvlp gun where needed but can
    also be setup to spray similar to a conventional gun but without massive overspray problems.

    I have both HVLP guns and the newer style high efficiency guns, as a part
    time painter I work better and get better results either working slow or fast
    with the non HVLP labeled guns i.e the Plus type guns.

    Before you go out and purchase a high end gun it might be an idea to
    purchase a low cost hvlp gun to get a feel for the process first then proceed
    from there. Whatever you decide make sure you can get replacement parts
    for the gun. Factor this into your purchase decision.

    This is where I was coming from when I said HVLP was bs.

    Thanks.... X

  11. #11
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    X,

    Are these guns you mention that fall in the middle ground, such as the DeVilbiss Plus, considered Compliant-type?

    And what would be the symptoms of paint not atomizing well...orange peel? or other? Because you can always just sand orange peel off, right?

    Thanks, Patricia

  12. #12
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    Hi Patricia,

    These guns would be considered by some to be Compliant-type. Devilbiss
    touts there gun to have the following features.

    Model No.
    GFG-670
    ======================================
    powerful atomization Twice
    the energy vailable n HVLP guns

    >>>>> Very important <<<<<<<<<<<
    ======================================
    Powerful productivity Super Fast
    fluid Flow for high speed painting

    >>> If running at full trigger, paint can be put down fast if needed<<<<
    =======================================
    powerful efficiency equal to or
    better than HVLP ransfer efficiency "From experiance.. "Better"

    >>>>>>> Very important <<<<<<<<<<<<<<

    =======================================

    Some symptoms of poor atomization would be,

    Heavy coating loaded with orange peel.
    Un-Even coating or needing excessive coats to hide primer undercoat.
    Using more paint than is needed.
    Difficulty in laying out the paint at a wide fan width, Paint would be heavy
    in the middle, dryer closer to edge of fan.

    On the ones above that come to mind, Peel would be a big one followed closely by un-even coating.

    You cant just look at sanding out peel as a simplified thing to do. For single
    stage paint you will spend many hours wet sanding away until the paint is flat. "Keep the word Flat in your mind"

    On a base coat clear coat application, typically you will see the peel in the clear as its technology is very similar to simple single stage paint. No big deal
    right just sand it out ??? "Wrong"

    Blow through that clear layer to the base coat, and you will be re-painting
    either the clear or both.. "Get the idea"

    The key to the whole process is the ability to lay the paint as flat or as some
    call as slick as possible. For BC/CC this means little or no peel in the clear.

    For single stage paint this means very mild or no peel.

    The other important factor is the Viscosity of the paint, that is also Key.

    Get the viscosity correct and couple that with a Plus technology gun and
    you will be off to the races or at least have a fighting chance right out the
    gate.

    When you start out painting things go wrong even for a seasoned pro.
    I am no pro... You stand a far better chance of achieving your desired
    results if you purchase a good gun. You will find yourself saying FU@#
    this a whole lot less and in general you will enjoy the learning experience
    alot more ! "Remember paint aint cheap, so you want it to go on even and smooth"

    On the gun options many local jobbers or your local automotive paint store
    might be able to give you a loaner gun to try before you buy. That might
    be worth checking out.

    Oh btw, you mentioned paint in a previous post. See my post today on the
    auto-air color water based paint, this paint might be a option for you.

    Best regards X

  13. #13
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    Quote Originally Posted by X711

    Before you go out and purchase a high end gun it might be an idea to
    purchase a low cost hvlp gun to get a feel for the process first then proceed
    from there. Whatever you decide make sure you can get replacement parts
    for the gun. Factor this into your purchase decision.
    HVLP guns are a novices dream, they are easier to handle because of the lower pressure coming from the tip but I would never recommend purchasing a low cost HVLP because they usually don't spray well.

    True the HVLPs don't break the paint up as well as a compliant but some orange peel isn't as much of a factor if you are planning on polishing the paint when you're done like most folks that want a good job and they will still need to polish even if they use a "compliant" gun. I would rather see a person lay down a consistant coating from an HVLP gun than a super smooth coat that has runs and dry spots that are more likely from a gun that has a higher pressure at the air cap.

  14. #14
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    Hi X,

    Thank you for explaining the results of poor atomization. I was under the impression any orange peel could always just be sanded out, but it sounds like if you have too much peel it can become a real mess.

    I've also wondered if you get minor peel in the color coat (why should it be limited only to the clear coat?), do you sand that out before clearing? Will it show if you ignore it and proceed and only sand out the clear?

    Len,

    So you recommend a high-quality HVLP over a compliant-type because the HVLP will generally lay down a more consistant coat with fewer runs, sags, etc. for a first-timer ("slow" gun)? And while the HVLP may cause minor peel, it is not so much that some sanding and polishing (which I certainly don't mind doing) can't remove? I certainly don't want serious peel problems such as X mentions...but that sounds like more what you'd run into with a cheapo gun that does not atomize well.

    Here's a thought I've wondered about: if I understand properly, the only way to avoid all/almost all peel is by using a "fast" gun that lays it out slick, which sounds more difficult to control for a beginner. So if I go with a "slower" gun I can expect some peeling. With this in mind, should I do extra coats of paint to allow for wet sanding some of it back off? I don't have any idea how many coats of paint get sanded off during the sanding/polishing stage and if that should be compensated for. How many coats should I be looking at for bc/cc (and that will allow a safety margin for lots of future detailing/buffing with a rotary machine)? At how many layers of bc and cc will problems show themselves from too much paint? My car, by the way, is stripped to bare fiberglass, so I will not have old paint underneath.

    Thank you, Len and X, for all your help! I'm beginning to feel like some of this is making sense.

    Patricia

  15. #15
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    Hi Patricia

    In a base coat clear coat system the base paint looks dull and flat, no shine
    to it typically its not so prone to orange peel.

    For the best result you need to get the paint on the panel to lay as flat
    as possible.

    If there is minor orange peel in the base coat you could sand it out prior to
    application of the clear coat.

    When you put the clear coat on the car, Every dust nib, small scratch thats
    on the base coat will show. If your using a dark color all these little imperfections will show up real well !. If there is orange peel in the base coat
    this will also show up.

    Thanks .. X

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