Whats the hype with HVLP paint guns?

Scott Long

Registered User
I see they are pretty pricey considering their standard counterparts. I can get a siphon feed gun for around $25 and a gravity feed for $65. If I step up to an HVLP gun it adds about $100 to the price. Whats the big deal.

High volume low pressure I think it means. I am just looking for a good gun to paint with and was thinking that I'm only gonna use it once or twice and then its gonna sit on my shelf, would I be ok with a siphon or gravity feed gun or do I need the HVLP? I know prep is the most important part of painting a car so does the gun make that big of a difference?
 
I'm leaning more towards the gravity feed since they have clear resovoirs so you can see when you get low, also I was told siphon feed guns will blow air if you run them low and that can cause the paint to splatter and cause you to have to resand and reshoot some areas.

I also see some guns listed as LVLP must be low volume.

Anyone recommend gravity feed over siphon? I think the gravity feed will be smoother because its pulls it down rather than up through a tube. Might be easier to clean also.
 
HVLP's have a transfer efficiency of 60-95%, while non-HVLP spray guns have a transfer efficiency of as little as 30-50%. Gravity guns feed better than the siphons do, but the siphons do have some advantages.
 
I was a painter from 1989 through 1993, so I'm a little outdated.

I prefered gravity fed over siphon fed.

HVLP was fairly new back then. They use a little less paint without filling the air with a lot of overspray, such as traditional siphon feed guns do.

If you are planning on painting a car, and want it to look good, then please buy Divilbis (spelling?) guns. One gravity feed to spray primers with and one gravity feed to strickely spray paint.

For my paint gun, I had two nozzles and fluid needles. One for base coat, and a little bit larger one to spray clearcoat.

Do not use lacquir primer. Only use two part urithane primer.
 
I just bought a gravity feed HVLP since I don't want to waste a lot of paint and have a lot of over spray.

Maybe I'll buy a 2nd one for primer, what is the advantage of using a seperate gun to spray paint and primer? Just so it doesn't clog up or ?

Also about the nozzles, the gun I bought says it has an adjustable nozzle on it so I can adjust the size of the pattern. Now when spraying clear coat do you want to spray a wider pattern than the actual paint itself?

Sorry, I'm new to this. I appreciate the advice.
 
The advantage of two guns is that you won't have to change fluid tips. i use a 1.7 for primer and a 1.3 for paint and clear, in my sata guns. i usually keep the pattern the same 6-8 inches, but change the overlap. primer and paint i overlap about 50%, and about 75% with the clear.
 
Ok I see now the tip size is different. That allows the primer to be laid on thicker?

What would you recommed as far as sanding grit to use before laying primer, and then after its primed, before laying paint.

I was thinking after the old paint is sanded off, use 300 grit to smooth it and then prime it, sand the primer with 600, then spray the paint. Should I sand the paint before I clear it? What grit would you recommend. Also after the clear is sprayed, is 1500 grit enough to wet sand it before I buff it and call it done?
 
the change in tip size is because the primer is thicker than paint and you do wanna lay it on thicker. i generally use 400 before primer, then 400 and 600 after. dont sand paint, just clear right over it. after i clear i usually hit it with 1000, 1500, then 2000. if you wet sand and buff too soon you'll end up dulling the finish, so make sure to allow enough cure time.
 
ok so if there is a drip or anything you still clear it and then sand it?

I would let it sit over night and at least 12 hours to dry before I wet sanded it. Is that sufficient?
 
if there is a run or sag, you can lightly sand with 600 or shave it off with a razor blade. i always bake and then let sit for 24 to 48 hours before i sand, but i dunno if you have that option available to you. just ask your paint supplier, they should be able to tell what will be sufficient for the products you're gonna use.
 
I will be doing this in a 2 car garage that will be cleaned thouroghly. All the sanding and washing/degreasing will be done outside so no dust gets in the garage. Then the car is gonna go in the garage get a final wipedown and then primed. It will go back outside to get sanded after its primed, and then back in the garage for the paint and clear. Its not a heated garage, but its sealed up very well and there's no drafts. I'd love a heated paint booth but thats not possible. Its a daily driver not a show car so it doesn't have to be the greatest paint job around. It will be my first complete paint job. I have some friends that said they will let me paint their cars after they see how mine turns out and will pay money so I could start doing this on the side as I get more experience.
 
thats a good way to start out, and it is an easy way to make some money, so good luck and cant wait to see the finished product
 
HVLP guns require a higher volume air compressor than a standard gun so make sure your compressor can handle it. Check the flow rating they require, they can be very significant.

Optimum tip size depends on the paint you're using and what you're used to. Make sure you practice.

Base Coat/Clear coat paints also put off VOC's that require the painter to use a self contained fresh air system.
 
I was gonna order a respirator, i can't afford the big suit and fresh air helmet i've seen at some body shops. I guess I'll have to frequently take breaks to get away from the fumes.
 
Just note that there are a limited number of respirators certified for proection from isocyanates that are the dangerious compound in the base coat/clear coat systems. 3m 6001 is one.

The isocyanates are colorless, oderless, and can create neurolgical and significant resperatory problems. The resistance to these compounds is very different from one person to another. With enough exposure even the most resistant person will become affected eventually.

Make sure things are well ventilated and that you track the usage on your cartridges as you won't be able to smell when they aren't doing the job anymore.
 
you should be fine. i just painted a trailer with single stage dupont, using a standard respirator. because i cant see crap out of my brothers "space suit". i was in a paint booth, but still, it wont kill you.
 
Single stage paint uses chemicals that are bad for you, but you can smell them. So anything that keeps the smell out should be good.

though single stage urethanes like Imron have their special breathing equipment needs as well.

If you haven't seen it yet, you may want to review this thread. I never did paint the car myself... yet. But the thread had some good info in it.
http://www.sccoa.com/forums/showthread.php?t=45673&highlight=paint
 
Thanks for the link Mike. I think I'm gonna just use some regular primer. I'll try to get it sanded down as far as I can, but I had to do some body filler in a few spots and I need to hide them under primer so that they don't show through the new paint. I had a spot of rust in the middle of the lower part of my drivers door the size of a quarter. It wouldn't grind down or sand with what I had so I had to get a small circle cutter and cut it out. There is a layer directly behind it so I sanded it and then used filler to build back out and smooth it in with the door. I'll go over the entire car with a dual action sander to get it all smooth and level before I shoot the primer.

I'm now leaning towards single stage paint since I don't want to mess up my lungs from the clear coat, and its just not feasible for me to buy a air mask and an fresh air system for my paint jobs. I plan to do my silver car first, once I get the experience and see how it turns out, I'll do my black car. I'm thinking a gallon of primer, a gallon of paint, a gallon of hardener, and a gallon of reducer should be enough for this job and will keep me at or under $300 for supplies. I just bought a gun, and some other air tools to use for other projects, so I've already got some money into tools for this project. Now I just need to get my garage cleaned out and push the other SC out in the driveway so I can park the car in the garage at an angle to give me the most room to walk around it and work.

After I get done painting the car I'll probably be so stoked I will want to repaint my riding mower. LOL.
 
Oh here's another dumb question but if I get a gallon of primer, do I need to add reducer/hardener to it before I apply it to the car? I would think maybe hardener but not reducer, but what do I know. I'm learing this all for the first time.
 
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