Bounceback w/HVLP??

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I finally tried using my new Fuji HVLP sprayer this past weekend. I'm painting the inside of a shelving unit made of plywood. Its rather deep, 22 inches. I started out with a Benjamin-Moore oil based primer ("Fresh Start"), which I thinned with mineral spiritis to get the 20-25 seconds in the viscosity cup as the instructions call for.
I followed the instruction book's recommendations; the air flow control fully on, the paint control backed out so the trigger wouldn't move and the air cap even with the nozzle. I then turned in the paint control until I was getting what looked like the right amount of paint on the wood, and painted the inside of one cavity. The result looks OK. It feels a little rough, though, as if I had used a water based finish and raised the grain.
From what I have read, the rough finish might be due to the paint drying too quickly, so I'll try adding a little Penetrol to the primer and see if that helps.
What surprised me was the amount of paint mist that came back at me out of the shelving unit. I wound up with dried paint droplets on my glasses, on my respirator, on my arm, in my hair, and on the gun. There seemed to be a paint fog in the air. Was I doing something wrong to cause that? I tried backing off the air control (and adjusting the paint control accordingly), but that didn't seem to reduce the amount of bounce back.
Can anyone offer any words of advice or wisdom?
TIA!
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Art Greenberg
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Art Greenberg wrote:

How far was the tip of the gun from the work?
I usually use my Fuji 6 inches or so off the surface. I'll normally get some finish in the air, but not what I'd call lots of bounce, once the air flow control (the one on the hose) is turned down.
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On Mon, 06 Aug 2007 13:16:54 -0400, B A R R Y wrote:

5-6 inches.

Its impossible to compare our experience without some objective measure. But I'd say I was getting a lot of finish in the air, much more than I expected.
My only prior experience with HVLP was at WW shows, where I sprayed an unknown paint (probably latex) onto a paper pad on an easel. And I did not see _any_ bounceback there. I'm sure the floor in front of the easel would show the paint color if there was as much as I've experienced here.
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Art Greenberg wrote:

The materials Robert mentioned that I spray without thinning time at more like 18 seconds on the included vis cup. With that stuff, I use a #4 setup with a gravity cup or #3 with the pressurized siphon or remote pot.
I'd try thinning further, or a #5 setup. The #4 is still pretty small. I'm actually familiar with Fresh Start and Enamel Underbody, but I've only applied it with a brush or roller. Both are quite thick from the can, but the Fresh Start version I'm familiar with is water based. Are you thinking of "Enamel Underbody" primer?
My favorite primers for spraying are BIN pigmented shellac and auto body primers. Either are dreams to spray, and can be overcoated by virtually anything. I've also used clear Zinnser Seal Coat as a paint primer, with excellent results.
You can also ask your local Ben Moore dealer if they have specific information for spraying. I poked around the BM site, looking for a data sheet. The only spraying BM mentions on paper for either "Fresh Start" or "Enamel Underbody" is airless, but they may be able to get local knowledge from the BM rep for HVLP.
If you saw latex sprayed at a show, chances are they had either a #5 or #6 setup (or another brand's equivelent) installed.
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On Tue, 07 Aug 2007 07:10:52 -0400, B A R R Y wrote:

I'm using the pressurized 1 quart cup, with the #4.

I'd have to order the #5. I can try thinning more - I have a small quantity of the already-thinned primer, and I can add more mineral spirits to it.

No, this is definitely Fresh Start. The can says "Fresh Start Alkyd All-Purpose Primer, White, 024 00". It is not as thick as their better latex paints, but it is pretty thick.

Thanks for the suggestions, something to try. Shellac might be good to experiment with, since cleanup is easier than with the oil based products, and it won't raise grain.
My first use of the sprayer, soon after I received it, was an experiment with unthinned oil-based Killz. It seemed to work OK on a test target (scrap plywood). Unfortunately, I left it in the gun while I stopped for dinner. By the time I got back to it a few hours later, it had dried in the gun. And since I could not get the nozzle loose (man, the factory put that thing on TIGHT), I had a very difficult time cleaning the gun. I ended up pulling the packing seals (and destroyed them in the process) and going into the gun block from the back to clean it. What a mess ... it took me 4 hours to clean it all up. I wasn't able to use the sprayer again until I got new packing seals.

I really should ask.
The data sheet for this primer says it can be sprayed, and it also says "do not thin".

Could be. I don't really know what it was that was being sprayed, but it was probably latex.
Thanks for your help!
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Paint BEFORE installing the backs .. what you're experiencing is pretty typical for the method you're using .. .. gotta think a little differently about your projects when yuo're spraying

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Art - sounds like you have the air flow up too high. And it also sounds like your finish is indeed drying too fast.
Contrary to what many believe, you can waste just as much finish in overspray and drift as you can with an HVLP system. I have a Fuji 4 stage, and during the summer months I rarely thin anything more than about 10%, and some things like oil based primer, not at all. I know Barry has a Fuji system too, and he doesn't thin much at all, if any. Try your product unthinned; you can always thin later if it is too thick. Remember, your viscosity cup is a guide, not a rule.
The second thing I would do would be to turn the airflow almost down to nothing and open it back up until you could apply the proper thickness coat without leaving an orange peel finish when dried. A good rule of thumb with HVLP is that you don't have more than 4-5 inches of bounce back when spraying. Keep the gun about 8" from the surface, and practice your spraying motion without anything in the gun to make sure you are staying uniform in this 8" distance.
Next - check your aircap. To shoot latex you should have something like a 1.7 mm fluid nozzle with the proper aircap. If you ahve that, you won't need to thin near as much.
Robert
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On Mon, 06 Aug 2007 11:51:43 -0700, snipped-for-privacy@aol.com wrote:

Robert,
Thanks. I'm shooting an oil based primer (Benjamin Moore "Fresh Start"), with the Fuji Super 4 turbine, XT gun and the #4 nozzle and air cap (stock setup with the XT gun).
I thinned by adding 4oz. of mineral spirits to 14oz. of primer. Is that 28% the way you compute it? Then 10% would be 1.4 oz. of mineral spirits. I started at 2oz., and IIRC that resulted in about double the 20-25 seconds the manual suggests.
I did try reducing the airflow, all the way to the lowest setting of the air flow control valve (the plastic ball valve that came with the sprayer). Is there a better way to do that? The Super 4 turbine doesn't have a speed control.
I probably was too close to the surface, too. More like 5-6 inches.
You've suggested a number of things I should try:
- Increase distance to surface.
- Thin less, maybe even not at all.
- Keep air flow low. Lower than the ball valve will go?
- Try adding some retarder.
Seems there could be a bunch of combinations of these. I'll try all of these together first, as it is clear I was too close and I need to slow down drying anyway.
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with the Fuji Super 4 turbine, XT >gun and the #4 nozzle and air cap (stock setup with the >XT gun). So far, so good. Great gun/system, great product.

This gets into a sticky commentary by "shooters". By total volume? By starting volume? WTF, over?
The manufacturers even differ on this way of communication. I am not sure which way the current wind is prevailing, but 4 oz on 14 is a deep winter blend for primer.
When you over-thin, you are spraying too much solvent for the product to perform as designed. It dries too quickly and sprays so thin it over atomizes. Sound familiar?

Make a half batch at that speed, and try it. I the summer time, I would try to spray first, then if it is coming out too thick, then thin the amount I had by 10%, which is roughly where you are in the second formula. During the summer, I spray either Zinsser or Kilz oil base, and don't thin either one. Make SURE you are getting enough material on the surface as too thin a coat will ensure that your surface dries too quickly making it rough.
Primer is strange stuff; it doesn't spray like a coating as it usually has some high metal solid content and some other polymers to seal that make it different from paints and sealers.
You will find that every new product you shoot will present you with these challenges. I suggest you keep a notebook of notes and conditions so you can go back to them when setting your gun up. Keep buying quality finishes and stick with them as they will give you the most consistent performance.

flow control valve (the plastic ball valve >that came with the sprayer). Is there a better way to do >that? The Super 4 turbine doesn't have a speed control. That is the best way. Make sure you have it mounted on the connection just under the gun. Don't worry about "speed controls". It is a turbine, not a blender. Turn it on, control the air flow at the gun. I think SpeedAire just needed something else to sell.

Wayyy to close. Actual spraying is a matter of technique. Your arm should look like one of those robots that paints car hoods. Exactly the same distance from the surface with exactly the same speed when spraying. I wasn't kidding when I said to practice that motion. Cut yourself a stick 8" long, and just before starting to shoot, put the stick in front of the nozzle so you can see the 8" and keep it in your mind while spraying. Sounds silly, but it works.
I only close that up when I have a difficult finish to apply or ugly conditions, but in any case these guns are not made to shoot any closer than about 6" as they won't develop the atomized pattern from the gun.
Since you don't get that satisfying hiss from high pressure spraying, it is hard to tell if you are doing what you need to do while spraying. Try running a couple of quarts of water through your gun. Spray on a fully sealed surface (or if the wife isn't around, the patio door!) to check out your pattern. You should be little more than misting your product onto your surface.

Yes.
Yes. Experiment. Take notes. Find a product you like and learn everything about it. This may take a bit of time and money, but WELL worth it. Make small batches to experiment with and you won't invest as much as you think.

Close the fluid knob completely. Open it up about 3 full turns and start there. Close the air valve completely. Open it a tiny bit at a time until you can see the coating atomizing properly. In my Fuji, this is only about 1/3 open! These units move a lot of air and have plenty of power. You may need to move it a little more open depending on the finishes, but try it from there.

NO retarder. First, you cannot retard primer. Second, why would you retard a finish that takes 20 minutes to skim over?
Spray the correct amount on the surface to begin with and you will be surprised at how slow it will dry. You should shoot for about 3 mil in application with the primer, and about 4-5 mil wet thickness with latex. It will dry fine.

together first, as it is clear I >was too close and I need to slow down drying anyway. You are on your way Art! Some practice and careful notes (repeatibility is everything!) and you will be spraying everything in sight!
Good luck!
Robert
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After reading/perusing this post last night, and halfway through spraying a sideboard, I tried your not thinning the Zinsser Bullseye on a test piece this morning and no matter how much futzing I did with the material/air flow I still could not get a satisfactory coverage/pattern with this POS gun/rig.
Since I did the drawers and doors yesterday the old way, I went ahead and did my usual 40 alcohol/60 shellac-out-of-the-can mix and got something I could live with. The humidity the past few days has been high. I had to leave the sideboard case outside to acclimate a few hours this morning before I dared spray it.
I do get some rough surfaces, but mainly on plywood drawer bottoms and places that don't show, because that's where I start ( to make sure things are going OK), but nothing that couldn't be easily dealt with using the old brown paper rub rub down trick.
I guess I just need to get a better outfit ... long as I'm cleaning, might as well be cleaning a good gun instead of this Chinese special.
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What make is that Chinese special?
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"Upscale" wrote in message

Campbell Hausfeld is the brand ... the cup, needle, spring and trigger are metal, most everything else is plastic. From all appearances, if you could make a spring out of plastic, this would have one.
But I only paid $149 about four years ago and have sprayed dozens of projects with it, so, in fairness, it has amortized itself and could be thrown away at little/no loss.
And I may have to do that soon as the cleaning process appears to have taken more years off it than actual use.
Then again, my Dad still has, and uses, the DevilBliss rig he bought when I was six, some 59 years ago!
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This may be a double post as I was called away and was unsure if I pushed "send or not".
As with everything I scribble electronically on this group, this is my opinion/observation. So we are sure we are both on the same page, please remember in context that the OP stated that he was painting, not clear coating.
I think the actual problem may be as noted, the equipment. I intentionally bought the Fuj as it has the highest air delivery of any unit I could find. Their gun was not my favorite, but hey... you can't have everything. And since I have learned to use it, the gun works great.
I would guess that the CHPOS probably is a two stage (or maybe a one!) that doesn't move enough air to deliver the thicker materials. But since you are or have been getting good finishes with your clear coats, it means that you know what your gun can do and are thinning properly.
However, if it is shooting clearcoat properly and not an heavy solids coating, that could mean two different things.
As far as shooting the shellac the first could be that with your lower powered machine (has Festool come out with an HVLP yet?) it may not be able to pressurize the cup and have enough air left over to atomize (we all know that is the incorrect term, but to stay on subject, we all understand the concept) the coating or paint and push it to the target.
Solution: Whether it is clear or Stain Block for painting(white) Bullseye, thin it with the proper thinner. With the thinner solution, give it more air flow and spray.

This high humidity and fast rising temps kill alcohol based finishes. For me, no matter what I do in this weather any finishes except paint are dicey. I can usually get some nice blush on lacquer with no problems at all with 87% humidity.
Spraying outside in the elements or in an unfinished (unairconditioned) house or in a garage is so different from spraying in nice shop. Now with the temps and humidity so high, I am glad I am doing mostly repairs and no finishing.
BUT... as they say, the show must go on. If I were in your shoes, I would drag out that shellac and really give it a dose of thinner. Here's my thinking - you know you can build the finish on these since the shellac will simply dissolve into itself. So I would take it from another direction to test it out. Think about it for a second; you know you are on the right track when thinner is better. Since you are essentially shooting resin with a solvent, who cares how much you thin?
I would cut the shellac by about 50% due to heat and humidity and then try it at 60 - 40 alcohol to shellac. The shellac will stick... it just depends on what you are trying to do with it. If it is a sanding sealer coat on a nice wood, you don't need it thick. Since the shellac will dry quickly, you can see what it will do on a test piece. I would thin the hell out of it then spray about a 3 mil coat on it and see how it does. That just may do the trick. If you like the results, it is certainly easy enough to build the coats. To me, it's worth a pint of material to try it out.
In a push job in similar weather, I was having so much trouble getting the shellac out of the gun I was ready to put it on with a heavy nap roller and be done with it. The dried coating texture would have been the same.
In a moment of really pissed off inspiration I thinned the Bullseye to a 70/30 alcohol to shellac (I also had the wrong aircap for the gun and couldn't get it to behave with the one I had with me) and it worked fine. I sprayed a pattern that was fairly thick, but since it was mostly solvent it dried thin (1/2 mil maybe?) and then in about thirty minutes (just able to leave a fingerprint in the finish) sprayed another coat spraying the opposite pattern. It worked great.
You can get away with thinning the daylights out of any resin finish (OK, to a point) since there are no solids to fall out of solution. You can thin them so much that they don't perform properly, but I wouldn't worry about that with shellac.

I dont' know if some of the stuff we get has green veneer or outgassing fish guts glue made with diesel, or what. But I never had that problem until a few years ago. I went for a few years thinking I wasn't doing the prep right, but now I think it is something to do with the wood.
Something is different, and if that is the roughness you are getting when you spray, I am getting the same.
So another voice is heard...

Will you be getting a new 4WD Japanese carrying case for it?
I am tighter than a top on a banjo, and I don't like buying new tools anymore. Just as an unsolicited opinion, I would probably goof with that setup a little more. If it worked for you in the past, it should work fine now. No, it won't have the power to spray some of the finishes as easily, but unless you are using finishes specially designed for HVLP you will be mixing up new formulas anyway with a new unit. As with any of this stuff, there is a lot to be said about being comfortable with a certain piece of equipment.
On the other hand, it sounds like you have sure gotten you money's worth out of it and more. It may be time... some of these new units are just nothing short of great.
Robert
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Considering the market, truck dealers should take a page from the 50's bank/gas stations promotions and offer your choice of Festool, Fuji, et al with each purchase.
Thanks for the comments, Robert.
My best luck so far shooting shellac with this CH rig is roughly 50/50 60/40 shellac - alcohol thinning, but with the table I need to do this morning, which is not of much import so will stand a little experimentation, I might kick up the alcohol in the ratio and see what happens.
To muddy if up even further, I've also had a big differences in the final results when using 99% Isopropyl versus denatured when the weather/high humidity is involved (I only shoot outside, and have to wait on the weather ... and the ubiquitous yardmen with a weedeater/leaf blower).
I usually thin with 99% isopropyl when the humidity is this high, and actually shoot it a bit closer to the surface. I don't analyze why, but it seems to work.
Like sanding, I dislike finishing, but the importance is all too obvious, so the piper must be paid in both effort and understanding.
Your (and Mike Marlowe's) analyzing helps ... thanks again!
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On Mon, 06 Aug 2007 13:26:51 -0700, snipped-for-privacy@aol.com wrote:

Uh ... yes!
Robert, thanks so much for all of your suggestions. I hope to get back to this this weekend. I'll let you know how I make out.
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Good luck! I hope it works out and you post some results. I will be out of pocket this weekend, but will certainly check back when I am available.
Robert
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On Mon, 06 Aug 2007 11:51:43 -0700, " snipped-for-privacy@aol.com"

I am just a beginner at this, and had my own set of difficulties getting my Apollo HVLP going right, but I got some excellent advice recently that set me on the right path.
Here's what the guy giving the lectures at the WW Show a few months ago told me, and it's working great.
But first - It was advice for Hydrocote and whether it would be equally applicable to paint I don't know. But, _too little air_ may be your problem. Or, it may just be that you're spraying within a deep area and having the mist "blow back" as a result (as others have said).
Anyway, the advice was: open the air ALL the way, open the material valve only a bit (for hydrocote). I looked up (on Hood Finishing's site) the proper amount to open the material valve and their recommendation is 1.5 turns for the initial coat, 2 for subsequent coats. Works Great!.
He sprayed a board to demo and it was a very fine coat. About 4 coats are needed. It dried very quickly (5 minutes or so - again he sprayed lacquer).
What I noticed after I started to practice his advice was that the room was no longer filled with a misty fog after I sprayed as it had been before. Which is what prompted me to post this after I read your situation.
My 2 cents or so.
Renata

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On Tue, 07 Aug 2007 15:08:13 -0400, Renata wrote:

Too little air seems counterintuitive. But the manual for the sprayer says to start with the air valve open all the way, which reinforces your thought.

Again, this is exactly the approach called for in the Fuji sprayer manual. And it is the approach I followed. After seeing the extreme bounceback, I tried backing off the air.
Robert suggested that I was way too close to the surface I was shooting. This might turn out to be the primary cause.

Thanks, I do appreciate your input, as well as all of the other comments I've received.
My fingers are crossed! I sure don't want to have to set up a bazillion CFM fan in a spray booth to do this work ...
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On Mon, 06 Aug 2007 13:46:26 -0400, <<<__ Bob __>>> wrote:

Thanks, Bob. Too late for this project!
Seems this doesn't reduce the bounceback, but instead lets it flow "through" the work?
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Art Greenberg wrote:

NEVER try finishing methods for the first time on the actual work. That's not to stick your nose in it, but we all need a reminder at times.
Make some 12"x12" panels of MDF or cabinet grade ply, and a small notebook. Properly prepare the panel for finishing by sanding, scraping, filling, etc... as you would with your best piece. Practice with the gun, noting EVERY variable, including material brands, gun options and settings, and time, temperature and humidity, in the notebook. Change one variable at a time until you get the hang of it. Keep the notebook handy with the finishing equipment for next time.
If you're not comfortable next time, spray a practice panel with the best known settings and get comfortable. In time, you'll automatically save decent cutoffs from your projects, and finish sand and scrape them with this step in mind.
Every time I've messed something up finishing, I was improvising on the actual work. After a few headbanging sessions, I realized that I didn't have to hit my head on the bench. Every time I fell like experimenting, I look at the ruined door that I saved and hung up as a reminder. <G>
BTW, 5x7 spiral notebooks are also great next to the sharpening equipment, router jigs, or with any tool that's infrequently used or has detailed setup information. I fly with checklists all the time, so I figured notes and checklists would be as handy in the shop. They are!
Please let us know how it all works out!
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