Turbine HVLP vs Paint

[Steve1]

I have a Fuji 5 stage turbine unit and the small G-XPC gun.  Normally I use it for spraying water based poly, but this week I decided to learn how to spray acrylic paint. 
I am painting doors, laid down flat.  It can't get an easier than this.
Not going very well so far.

I am using Benjamin Moore Regal Select semi-gloss (35.5% solids)

First two attempts were definite failures and I will spare you the details.

Third attempt, I am getting closer.  1.8mm nozzle.  I thinned to 27 seconds on Ford cup.  Some Floetrol, but mostly water. 
I narrowed the fan to get better atomization, but then I had to open up the fan size somewhat because spraying white on white I had a hard time seeing where I had already sprayed.  Distance about 6".  Not bad, but I could see a higher gloss level where (I expect) the paint went on thicker.  Having difficulty spraying a "wet" surface.   
View attachment 1

Fourth attempt (different door) I thinned to 33 seconds.  Some Floetrol but mostly water.  1.8mm nozzle.  I kept the fluid flow low to get good atomization, so I was moving the gun painfully slow and taking multiple passes.  On a practise sheet, when I opened up the flow more, I started seeing spatter on the outside of the fan.    I got closer with the gun, about 4-5"  Still, I was not seeing a wet surface, so increased the fluid flow.    I could see the air from the gun making ripples on the paint on the surface.  But at least it was a wet surface.  Not really orange peel, but not a smooth surface either.  (photo is only 2 hours later)
View attachment 2

First the basics -
What should my target viscosity be ?
How far should my gun tip be from the workpiece ?

Any advise on how to achieve a good wet surface without opening up the flow too much ? (that was attempt #2, had to sand)

 

[woodferret]

Can you get 518 Extender?  That's BM's retarder.  Seems like floetrol isn't really stopping it from drying fast - yes, it is an extender, but my experience has always been kinda meh.

Also, try 10".

 

[usernumber1]

I call these paints 'airless gun paints'. If I use the HVLP I use a 2.2mm needle and slow down the fuji to a half-ish so it doesn't blow so much around.
Thin accordingly so it lays out thick. It really depends on your humidity and temperature as well.

These paints level a lot more than a poly finish so I would err on thicker side. There's a mil gauge that came with the fuji system, you should use when you are learning new paints.

 

[Packard]

I have a stage 4 turbine.  I use Benjamin-Moore Advance.  I didn’t have any issues so I didn’t have to play around much.  But I use like 90 to 120 seconds on the Ford cup.

Light colors, and especially white, cure much harder than the darks.

In the Advance lineup, high gloss is listed as an exterior finish.

I brush Advance also.  But it takes about 12 hours for a recoat.  But the extended dry time means it self levels nicely.

 

[Steve1]

Thank you.
Getting better.
My root problem was that I was trying to follow instructions.
The instruction book that came with my Fuji gun says to thin latex paint to 20-30 seconds. 
I have another Fuji Quick Reference Sheet that says the same thing.  But I found another Fuji Quick Reference Sheet that says my G-XPC gun can spray 31-60 seconds material.  Interestingly, absolutely nowhere can I find any recommendations that relate suggested viscosity to the number of stages in my air supply.  I bought the 5 stage specifically because I wanted  the ability to spray paint.

Fuji Customer Assistance was very helpful.
They said I was thinning it way too much (just like Packard suggested)
They suggested I thin to 37-50 seconds and not use any Floetrol. 
And try to put down a thin, wet coat.

I got much better results.
But I still have one problem
I spray first the rails, then the stiles.  There is a always going to be some overlap, and the overlap is visible.  The overlap is smooth and glossy, so I figure this is the ideal, and the other areas are light in thickness of paint.  See image below.

Door needs another coat anyways.  Any suggestions on the best technique to blend the rail/stile overlap ?

 

[Steve1]

Well, I keep making progress.

I keep increasing viscosity.  Last spray was 70-72 seconds.  1.8mm cap set.  Been using some Floetrol and water. Atomization on my test paper was probably not ideal, but I don't think it negatively effected the finish, other than it wants to go on thinner at higher viscosity.

I have been spraying first totally across the 30" width, then the 80" length.  A bit of a stretch across the width, and I have to walk along the length which makes it difficult to keep a straight line, but I guess I just need more practise.  I don't want to stand the door up and risk runs.
Result not perfect but not bad.  In the right light, I can see where paint was thicker (or maybe thinner?) and levelled better.  Still, I think this door is a keeper and I move on to the next door.   
I think I gotta try to lay down the paint heavier, probably with more passes rather than more flow.

 

[makpacman]

It sounds like you're doing fine on the viscosity now but spraying with any new equipment does take a fair amount of practice.

Some of my advice may go against the directions a but I've been spraying like this for 30 years and am able to approach factory finish results nearly every time I spray.

First, I don't use a Ford cup. I'm a contractor and don't have time for the cleanup nor the patience of a saint to wait that long before I modify the viscosity., which I may do 4 or 5 times, but all within 1 or 2 minutes total.

I use an ordinary stir stick. I thin until the first and second drips off a corner of the stick are between 1 and 2 seconds apart. When they're 2 seconds apart material can usually be sprayed out of a 2.0 tip/nozel combo on a 5 stage turbine such as yours.

When it's ~1.8- 1.5 seconds between those drips the 1.8 tip works, even with a 4 stage turbine. 1 second works with a 1.5 tip and thinner solvent based materials such as B.I.N primer for example.

For your door I'd set it up so I can spray the entire door from one side and turn the air cap of my gun to spray a horizontal pattern. Using vertical strokes spaying across the short side I'd spray the entire door in one go and then spray around it getting the edges using a vertical spray pattern held 6" away at a 45° angle.

Hopefully, and in my experience it almost always is the case that the paint will be wet enough so it all glosses over still and thick enough yet thin enough to not drip. This can be checked and minor touches can be made for up to 1 minute.

I'm sure I've missed some things here but you're close to getting the results you're after.  Good luck.

 

[Steve1]

For your door I'd set it up so I can spray the entire door from one side and turn the air cap of my gun to spray a horizontal pattern. Using vertical strokes spaying across the short side I'd spray the entire door in one go and then spray around it getting the edges using a vertical spray pattern held 6" away at a 45° angle.

Thank you.
A helpful (and should have been obvious tip) tip here.  I had the fan vertical and been turning my wrist when spraying across the short side.

Interesting that you spray in one pass. 
I didn't think I had enough air supply (even with Fuji-5-stage) to open up the fan and open up the fluid flow to do one pass.
And you do that with 4-stage ?

Yeah, thinning and measuring with Ford cup is tedious process.  But the last thing I need now is to introduce another variable of inconsistant thinning.  Maybe one day I will get to point of being able to thin just by looking at stir stick.

 

[makpacman]

Interesting that you spray in one pass. 
I didn't think I had enough air supply (even with Fuji-5-stage) to open up the fan and open up the fluid flow to do one pass.
And you do that with 4-stage ?

Yeah, thinning and measuring with Ford cup is tedious process.  But the last thing I need now is to introduce another variable of inconsistant thinning.  Maybe one day I will get to point of being able to thin just by looking at stir stick.

Let me rephrase that. By one pass I meant I'd start at the top corner and spray towards me to the near corner, stop spraying, shift over 6 inches or so, spray again going in the opposite direction back towards the other side, stop, shift over 6" etc. until I get the entire surface sprayed.

I'd also have a worklight higher up but on the far side that can be used to quickly check my surface is getting a uniform coating from time to time.

And the 6" movement should be taken with a grain of salt. It depends on your fan width. I'd probably shoot for 1/3 overlap with a small cup.

To answer your question about my equipment, yes, currently spraying with a 4 stage Fuji Mini mite, T70 gun, 3m pps cups.

As far as not changing the method used for viscosity measurements, you're correct. I only mentioned it because Titan Capspray 5 stage turbine used to come with a small pointed stir stick and instructions "similar" to what I listed as the only viscosity measurement tool. Had it not been for that I would never have kept painting as the Ford cup drives me crazy.

To me the Ford is more for $100/gallon clearcoat on an $30k car. Then yes, the ford cup is not only very informative it's highly cost effective as well. Usually I spray $5 worth of paint on a $100 door though.

As you said, viscosity becomes more intuitive over time. Remembering my first few pancake batters, it's an oddly a tricky discipline in the beginning .

Inexpensive accessories that can help out include a milk crate or two, triangular pointed stacking blocks, and a 10" lazy Suzanne ring.

 

[woodferret]

PPS cups help a lot in dialing in the viscosity too I find.  With 'new' paint, having the markings on the side allows you to dilute a tad more and keep track of it when you're spraying on test pieces.  Using math you can back out the actual dilution ratios along with any catalyst/retarder for future batches. 

I guess you could dump out the standard cup too and measure that way... but I'm lazy.

 

[Packard]

If you record your recipe for the ideal viscosity determined by the Ford cup, going forward is fast and easy.

Let’s say you measured out one cup of paint and two ounces of water to obtain the desired viscosity, then the next time you only have to measure out the paint and water.  No Ford cup required.

Note: The recipe will only work for same paint from the same manufacturer. I tested the B-M Advance, and color change, and gloss change did not affect viscosity. You should confirm the same for the paint you choose to spray.

Amazon sells clear disposable mixing cups with calibrations printed on the cup.  I makes things easy.  They are typically sold with no lids.  I find lids handy and I always order some.

 

[Steve1]

I will also need to get better lighting so I can better see issues as I am spraying.

Working in my garage.  I raise the door a couple of feet so I can put the turbine unit in fresh air, but really should open the big door all the way for better lighting.    Also will bring my rake light next time.

 

[Steve1]

If you record your recipe for the ideal viscosity determined by the Ford cup, going forward is fast and easy.

I keep moving up on the viscosity, targeting 10 seconds at a time.

Last spray was 70-72 seconds.    You figure I should stick, or move up some more ?

 

[woodferret]

Cover your rake light with tape or plastic

 

[makpacman]

If you record your recipe for the ideal viscosity determined by the Ford cup, going forward is fast and easy.

I keep moving up on the viscosity, targeting 10 seconds at a time.

Last spray was 70-72 seconds.    You figure I should stick, or move up some more ?

Are you happy with the results? Ideally, the manufacturer wants their product applied undiluted for best results. Additives, even water, are considered impurities and can hinder the performance characteristics of the paint. I.e. Not as hard, not as elastic, and/or not as much UV resistance.

Generaly, I look to spray as close to stock as I can get good atomization with, and this is determined similarly to how you're doing it - through trial and error. However, I prefer testing with too thick then thinning from there until I get acceptable results.

I keep a notepad and pen handy to jot down working formulas. These are edited and "usually" do improve over time.

Keep in mind that if the doors are new and came pre-primed, sandable primer, and lots of it, may go a long way toward creating that gorgeous hand that factory finishes have. It's usually less expensive than the paint and dries faster so in the long run, it's a win/win.

 

[Packard]

The slow drying Advance self-levels very well as long as I spray with the doors or drawer fronts flat on a table.

It is also susceptible to runs or drips if shooting vertical panels.

And while I fully disassemble my spray gun after each use to clean, I found that if I rubber band a small piece of a plastic bag over the nozzle, I can leave it dormant for 2 - 3 hours (maybe longer—I never tested).

So if I have a cabinet box to shoot, I can put it on painters’ triangles and shoot the horizontal surfaces, wait an hour for the paint to set, and then rotate to paint the other surfaces.  Obviously a slow process, but I can get the results I like.

However, there is a noticeable difference in color on end grain.  So I use mitered corners for the rails and stiles.

 

[Steve1]

Are you happy with the results?

I'm not satisfied with the results, so I increased the viscosity to 82 seconds.  Some floetrol, but mostly water.
Opened the garage door fully and had the morning sun behind me.
With the help of suggestions I received, I got very uniform coverage.
However, not a great texture.  See below.  I don't think atomization was not particularly good.  Looked gritty as I was spraying.  Some of it levelled out, but not totally. 

Door was pre-primed, but seems the robot was having a bad hair day.  Not a good surface on it to start, but I sanded the primer before spraying paint.

I still have no idea where I am going wrong.  But I don't give up easy.
Any suggestions ?
Looking back at my previous results, the only places I got beautifully smooth finish is where I overlapped the spray on the rails and stiles --- so simply not thick enough ?

 

[Packard]

Just to throw a wrench in the works:

Benjamin-Moore’s Advance dries much, much harder than Regal Select, and color match is a guarantee. 

I would paint a residential door with the door flat on a table, so no runs are likely. 

I’m of the opinion that Regal Select (my paint of choice for walls) is a wall paint and that other paints do better than R/S for trim and doors.  Especially doors, which are more likely to get hand prints or soil than walls. 

I also brush Advance using 3 very light coats brushed out so that no runs are possible.  The end product looks sprayed.  But note the very long re-coat times for Advance.

Also note that I have had issues painting Advance over any shellac based primer.  The Advance crazed and had to be re-primed and re-painted. 

 

[woodferret]

I still have no idea where I am going wrong.  But I don't give up easy.
Any suggestions ?
Looking back at my previous results, the only places I got beautifully smooth finish is where I overlapped the spray on the rails and stiles --- so simply not thick enough ?

I assume you're well over the 236ml/L dilution?

At 80ish sec, you're more water than solids, hence the mottled pattern.  It's overthinned, and the water is also vaporizing coming out of the hot tip.  What does get onto the board is coalescing around the spittle like snow-flakes in the sky.  Since there's little solids, they're leaving voids.  I really suggest using the right retarder.

edit: funny aside - I type in 'snow-flakes' (without the hypen) and it posts as 'complainers'.  LOL.

 

[Steve1]

I assume you're well over the 236ml/L dilution?

At 80ish sec, you're more water than solids, hence the mottled pattern.  It's overthinned...

Have not been tracking volume.  I have been working towards a viscosity target.

What viscosity would you suggest I target ?