Re: Bounceback w/HVLP??

On Aug 6, 2:37 pm, Art Greenberg <n...@xxxxxxxxxxxx> wrote:

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).

So far, so good. Great gun/system, great product.

I thinned by adding 4oz. of mineral spirits to 14oz. of >primer. Is that 28% the way you compute it?

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?

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.

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.

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.

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.

I probably was too close to the surface, too. More like 5-> 6 inches.

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.

You've suggested a number of things I should try:

- Increase distance to surface.

Yes.


- Thin less, maybe even not at all.

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.

- Keep air flow low. Lower than the ball valve will go?

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.

- Try adding some retarder.

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.

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.

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

.

Relevant Pages

  • Re: Spray Finishing - HVLP v. Airless v. Air-assist
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  • Re: What compressor and sprayer to buy for auto clearcoating?
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    (rec.games.pinball)
  • Re: What compressor and sprayer to buy for auto clearcoating?
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    (rec.games.pinball)
  • Re: Spray Painted Surface Very Rough
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