Hvlp versus conventional spray gun

BULLSEYE!!

The "V" in HVLP means VOLUME and your AIRPRESSURE needs to have VOLUME of airflow to make the gun function. If you have inadequate air volume from your system either too small of an air compressor, or too small of a feed line to your gun or any regulator or fitting between your air source and gun that restricts the flow, it will decrease the performance of the gun. HVLP also increases the fluid transfer, so more material is being applied. You also need to use thinners and reducers that will flow the excess material smoother, usually a grade slower in evaporation temp (reducer) than you would use in a conventional spray gun. The higher air pressure in conventional spray equipment does tend to evaporate some solvent in the spray process. Orange peel is more prevelent in newer paints with HVLP, because most newer paint systems are made to be baked which reflows the paint film as it is heated.


All of the above is usually not possible with a low buck small air compressor and small airlines in the basic home garage.

Most production painters deal with this everyday and have their materials, system, and technique "dialed in" with their equipment. It's a fairly big leap, for a once a year garage painter, to get all the equipment and materials working together for one job.


Gravity feed guns (non HVLP) are a real good in between for the garage painter. They still have a more efficient fluid transfer than siphon feed guns and produce good results while saving some material and lessening overspray. They are also easy to get good with.

I'm still a fan of conventional spray equipment for my garage paintjobs. I get good results with low buck equipment. If I were still spraying for a living, I would be heavy in the HVLP mode.

overspray

 

Orange peel is one thing, the bumps I sprayed were big enough to call breasts....millions of breasts all over the car...big nipples, little nipples.....you name it I sprayed it trying to figure out that piece of shit over the course of several paint jobs. I finally got tired of wet sanding and buffing everything trying to fix the shit.

 

I like nipples!

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Here's the whole post I did when helping Eyeball get ready to paint his 32 roadster.

http://www.jalopyjournal.com/forum/showthread.php?t=225633&showall=1

 

Even going shop to shop can be a pain.... different systems, steel lines,where and how the traps/ filters are setup. Being able to adapt is an acquired skill, when in doubt pull out the old #7's and have at it.

Everyone takes their knocks but what is a shame and often funny at times too is having a tech school kid brag on his $1200 digital gun but he can't get it to work. I've cleaned the upholstery glue out of my junk Sharp just to prove the point that it's the painter not the gun.

 

the new epa rule 40 cfr subpart 6h will change a lot of the hotrodders mind on hvlp guns, it seams that by 2011 you have to take the epa test and prove that you can use a hvlp gun, and will have to show your card to buy paint, !!! it's all comming boys ,the old days are slipping away, the home shop painter ain't got a lot to worry about, be the shop owners will !!!! it will cost a lot $$$$$ if you get caught, so don't get caught ???

 

All I've learned is tip size is important ,50 lbs at nozzle ,I switched over but It is still trial and error ,Manufacturers only give you tip sizes for new paint ,I used a 1.6 for Enamel Centari .Next time I paint Im gonna try a 1.4 .....1.6 Came out peely Cut and buffed ,As far as pressure at tip ,I have no idea how to measure this....

 

The HVLP is a little different. I use a Devilbiss gravity feed with a 1.2 mm tip. It's as close to the good old JGA as I can get. Atomization was the problem I always had. The HVLP's always seem too heavy. I find I can spray with 20 - 22 lbs. of air pressure at the gun and it works great. I use a lot of light triggering to get the atomization I want. I remember a painter telling me that with a HVLP you put the paint on like using a brush. Slower and heavier!! You'll find once you get use to it, it works well. Here's some of my paint work with the HVLP. The Green Jag. is off the gun and the Black Ford P/U has been colour sanded and polished.

The Old Tinbasher

 

Because ALL manufacturers had difficulty with "mid coat adhesion", meaning that there was an issue with the bond between the base and the clear.

I can't say what caused this with your Honda, but if my clear flaked off it would probably be because I let the base dry too long before clearing and did not sand the base to make up for the loss of the chemical bond.

The paint IS better today, but it is more expensive also.

 

I have tried many different guns as a garage painter. I think painters relate to the gun like women, you try like hell to figure them out, bitch about them and blame them when it goes bad. Then go out and get another one.

I use an Iwata LPH400. If you took it away I'd quit. I do believe that a good painter can compensate for inferior equipment, but an inferior painter needs good equpment. "Reading" the spray pattern is key, the paint needs to be thinner than in the older days and I lay an extra coat and slightly slower reducers / activators in my clear. I also recommend reading "setting the gun" on SPI's website. If the coats are thinner, there is more solvents to flash out. Too many guys put too much material on for the air pressure used. Here are a couple recent jobs sprayed. (please dont LOL). I'll admit that I "nib" and buff because I hate dirt and I believe that I will never get a dirt free finish.

Hopes this helps.

 

35 I agree, I believe a lot of the problem is mixture thickness coming out of the gun. back in the day we had high pressure guns so the reduced material was broken up more coming out of the nozzle. Newer paints are higher viscosity, (thicker) materials. I use a cheap, I mean cheap NAPA HVLP, 1.4 and 1.7 nozzle sizes for base, clear guns. For base colors it's no big deal, reduce 1 to 1. For clears I always over reduce and move faster, still using the lower air pressure for the HVLP. I get comparible finishes to what I use to get with a #7 binks siphon gun. I always color sand and buff all my jobs so that's not a big deal, but the amount of color sanding is, so I always like to get as nice a finish texture as I can. It's a fine line when applying the clear. I think a lot of us try to get factory finishes in our home workshops from the current paints. The current finishes are designed to be used by shops that have well ventilated, ie, downdraft booth's, or good crossflow booth's with plenty of airflow across the vehicle and baking capabilities. These new paints are not designed with us home shooters in mind. Take for instance the runs you may get in your home brewed job. You shoot it like we use to..air pressure, gun setting ect and wonder WTF, why am I getting runs? It looked fine a minute ago. Well, you don't have the airflow to pull the solvents away quick enough to make it dry at the correct rate. So what you thought was fine,(which would have been 20 yrs ago) is now NOT RIGHT for the type of materials you are now applying. Capish? Reduce the clear more and move faster. Put on more coats, not the high build two coats that are recommended . JMO, your results may vary.

 

Reread Overspray's post #31...dead on the money.
the only thing I would add is that HVLP was pretty new technology 10 years ago and alot has been learned since then.
a newer RP or "compliant" gun with a smallish (1.4 or smaller) tip will usually work pretty well in a poor guys garage. Plan on about 100-150 bucks for one.
Satas and Iwatas rule the shops around here,but most of us don't paint enough to warrant the price tag.
$69.99 for a 3 gun kit = junk...don't bother.
I also wonder if the 40 year old lacquer job sits outside all the time and has never been waxed?

 

old thread, excellent topic- the sharper guys in the painting industry have learned to read between the lines, in regard to HVLP. like most new technology, there's some bs-ing going on. first off, true HVLP was a pressurized system powered by a turbine, and the spray gun head was a bleeder type- meaning air constantly exits the air cap, and paint was bled into the airstream when the trigger was pulled. these types of spray guns atomize very well- even the cheap ones made back in the day with the screw-on cups. most of them had a plug or knob that could switch the cup from siphon feed, to pressure cup. I got one for $5 at a yard sale, it looked like a piece of junk- but it atomized paint into a fine mist amazingly. when HVLP was later mandated by law, the guns marketed as HVLP weren't really HVLP per se, in the traditional sense. they were simply air limited caps with small tips for the fluid nozzle- a choked down spray gun. you could achieve the same results by putting the smallest .040" "33" air/fluid nozzles and needle tip, in an old Binks #7, and turn down the needle adjustment and air pressure- presto- you have an old siphon feed gun that will atomize and save paint, just like an HVLP- and will spray BC/CC urethanes and today's thinner paints. but you're making the adjustments mechanically, manually, and a custom setup choice of air cap, nozzles, needle tip yourself- rather than already being built into the gun as sold. the old siphon guns were sold with a relatively "rich" setup for paint, and huge spray pattern, to be used with high air pressure- to save time, and paint fast.
what makes an HVLP gun HVLP, is limited size air caps and fluid nozzles. whereas old school guns could be bought with huge needle valves up to .120" back in the day, a "big" HVLP nozzle is .070", and most are smaller than that- around .030"-.060"
there's a video up on youtube where an old painter come right out and says, "listen guys, you don't have to bs people- if your HVLP gun is pumped up to 60 psi, it's not really HVLP anymore" - and he's right. what many painters are doing is cranking up the air pressure on HVLP guns, to where it was on the old siphon guns years ago.
IMO, even turning it up to 30-40 psi isn't really HVLP. We used to spray lacquer at that pressure, to reduce overspray and orange peel, when doing a blow-in spot repair on a fender or door.
in reality, you can install smaller caps/nozzles/needles in any old siphon feed gun, and turn the needle in to lean it out, and move in closer with the gun and you're basically painting the same as any HVLP. it's just that with the new HVLP guns, the entire gun and nozzle setup is already leaned down to begin with. think of it as this- instead of being adjustable on a scale of 1 to 10, it's only adjustable on a scale of 1 to 5. the stops are set lower by the orifice sizes in the gun and nozzles/air cap.
what makes a new gun HVLP ? a smaller air cap. smaller caps atomize finer. larger caps throw more paint, but give a textured finish. time to wake up and smell the coffee- HVLP is a gimmick, it simply advertising.
think of it as this- first there was mono music recordings- then stereo- then quadraphonic- now there is surround sound. first there was shellac records, then vinyl, then reel to reel, 8-track, and cassette. now there's CD.

but if you have a really good old 1976 Pioneer 200 watt, silver faced stereo amp and speakers, that's all you really need to play Dark Side of the Moon on 33rpm vinyl. your electric bill is going to be higher with the old amp, it's going to waste a few more kilowatts per month. (laughter...) but it's gonna sound really good- as good as that new CD surround system, and probably even better. it's all relative. a lot of the perceived technological "gain" of HVLP, is simply pumped up advertising and hype- ushered in by the emissions laws, and federal/state mandates. remember, first they outlawed the old spray guns, then they told us the new ones were better.

sorta like they stopped putting the 426 Hemi in Chryslers in the early 1970's, by outlawing it for emissions....and later told us that a 318 with lean burn was better, cuz it got better mileage.

yeh....right....