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Forum topic by Sunnygirl posted 02-06-2012 07:52 PM 1805 views 0 times favorited 7 replies Add to Favorites Watch
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Sunnygirl

37 posts in 1851 days


02-06-2012 07:52 PM

Thanks to all for the great input on orange peel with waterborne poly with HVLP. I realized my room temp (garage) was too low, and also heated the finish a little, and could see a huge difference. Still got some orange peel, so have a couple more questions.

I used a viscosity cup and got a time of 20 seconds. Does this sound right for waterborne poly? I’m using a 1.3 nozzle. I looked in my owner’s manual and it doesn’t state the time for waterborne poly. The gun is a Maxum II on a Capspray 105 turbine.

I still got some orange peel. Some of it leveled out when dry and some didn’t. The problem is, I don’t know how to tell which ones will flatten out and which ones won’t. I was expecting to see a nice flat finish when I sprayed. What should I see when the finish first hits the surface? Should I see orange peel that eventually flows together, or should it look nice and smooth from the beginning? If I should expect to see orange peel initially, how can I tell that I’ve done it right and it will eventually flatten out? I’m just not sure what I should be seeing as I’m spraying.


7 replies so far

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JAAune

1646 posts in 1784 days


#1 posted 02-07-2012 06:16 AM

That’s a pretty hard one to describe. In my experience, water-based finishes look like orange peel when they first hit the wood. Also, if the finish starts to look milky, you’ve got way too heavy a coat.

The best way to get a sense of how it should look is to make some test boards (twice as many as you think you’ll need) and practice in a controlled manner.

Before I go any further, I’m guessing you need to increase the light in your finishing area. Don’t worry too much about the ambient light but do get plenty of strong task lighting to shine on the stuff to be sprayed. The amount of light put out by a 1000watt halogen work light set (or even two sets) is pretty good when combined with decent ambient light.

I’m not necessarily recommending halogens. They get really, really hot. Never use them for sure if you are spraying flammables. They are a viable option for non-flammable finishes though – especially if the room is on the cold side. Whatever the light source, get something with equivalent output.

Keep the lights shining from a low position. You want a raking light that makes it possible to see the reflection of the wet finish. This will make it really easy to see how much finish you have on the wood.

When practicing, start by applying a super light film on the first sample board. Make this one so light that it doesn’t even cover the surface completely. Also, number all the samples before spraying so they can be identified later.

Do the same with more sample boards but with each successive test, increase the amount of finish slightly. By the time you get to the last board you should be spraying such a heavy coat that the wet finish looks milky white.

Let all the samples dry completely. You’ll soon find out which ones seem to get the best results. So far, with the products and techniques I’ve been using it takes around four coats of finish to get a similar build to what I’ve be accustomed to see with two coats of pre-cat lacquer.

Also, are you positive that what you call orange peel is really orange peel and not fisheye or some other defect? Look at the following site for some pictures and descriptions of similar types of finish defects.

Finish Defects

-- See my work at http://remmertstudios.com and http://altaredesign.com

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404 - Not Found

2544 posts in 2437 days


#2 posted 02-07-2012 04:44 PM

It sounds like you are doing all the right things to beat this problem…

from the Fuji Handbook – you can find this online

VISCOSITY GUIDE
To test the viscosity of the paint material, fill the viscosity cup to the brim
and time how long it takes for the liquid to empty out through the hole. We
recommend you experiment to find the ideal viscosity for your application
and record the information for the next time.
The chart below is an approximate guide to thinning. Note that the viscosity
cup has a hole in the bottom. To check viscosity, dip the cup into the
thinned paint and time how long it takes for the paint to run out of the cup.
Cellulose 18 -20
Cellulose Primers 18 – 20
Lacquers 18 – 20
Sanding Sealers 20 – 22
Enamels 20 – 25
Stains Undiluted
Latex 40 – 50
Creosote Undiluted
Oil-based 20 – 25
Polyurethanes 15 – 18
Remember, as a general rule, most ‘paints’ you purchase over the counter
were formulated for using with a brush and are too thick to spray successfully
without thinning. This includes all lacquers, enamels, oil-based
paints, latex etc. There is usually no mention of thinning for spraying so
you will have to experiment. We suggest around 25% to begin with but this
may contravene the air quality control rules for your location, so please
check this by calling the paint manufacturer. The solvent used for thinning
is usually the solvent mentioned on the can in the instructions for ‘cleaning
the brushes’. However, if you are unsure, please check with the coatings
manufacturer.
HVLP spraying is more friendly to the environment than most methods of
spraying. It reduces appreciably the amount of unnecessary misting and
fogging (overspray) associated with high-pressure spraying. Spraying with
Nitrocellulose lacquer can be hazardous. The lacquer, fumes and
overspray are toxic, flammable and explosive. If spraying must be done
inside an enclosed area, ventilate well. Spray close to an open window or
door and situate a fan to draw out the fumes (an explosion-proof motor
may be necessary). PLEASE CHECK WITH THE LOCAL AUTHORITY
HAVING JURISDICTION IN THIS MATTER.

It might worth thinning the finish a little more.
As to the question of should you see orange peel when you’ve sprayed, no, just a flat, wet coat. I wonder if the problem is with the gun – would you be able to disassemble to nozzle and check that there’s no dried material in it, as well as the aircap, to make sure the air flows freely to form the fan.
Also, check the cup seals if it’s a pressurised pot, may be affecting the material flow.
If you were to spray these test pieces standing up, would they have runs in them?

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Sunnygirl

37 posts in 1851 days


#3 posted 02-08-2012 02:25 AM

Good advice. I’ve tried to be meticulous about eliminating all variables I can. I’ve cleaned the gun extremely well and have great lighting (3 bright lights total). I can really see the finish well as I’m spraying. Just unsure about what it’s supposed to look like while it’s wet. I talked to a furniture guy locally today who told me it looks like orange peel when it first goes down. That makes it hard to determine when I’m doing right…. will have to wait for awhile to even know if I sprayed it correctly or not. Also have the variable of adding more or less air to the mix. Wow, this is difficult.

I’ll try the sample boards and see what I can do with it. Thanks so much for both inputs. Renners, what type of finish do you use? Sure would be nice to be able to see a nice flat wet coat. Maybe I can work toward that.

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Sunnygirl

37 posts in 1851 days


#4 posted 02-08-2012 05:52 PM

Renners, what type of system are you using? Is it turbine or compressor? The turbine uses hot air, which might make a difference. Also, what finish do you use? That could make a difference too.

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TheOldTimer

226 posts in 2553 days


#5 posted 02-08-2012 06:13 PM

I have been using water base finishes for years, mostly lacquor. I set my viscosity to 18-20 and have had excillent results. I also add retarder to my finish to lengthen the drying time allowing the finish to flatten out before drying. I live in the desert so the finish dries very fast with our low humidity. In the spring and early fall, spraying water base here is impossible as the first pass is dry before the third pass is made. I switch to regular lacquor if the weather is too hot. As previously stated do not apply your finish too thick or you will get orange peeling. Light coats work best. During the summer months, finishing outside is impossible here with temperatures of 115-120. That’s the price for 72 degree days during the winter months.

-- TheOldTimer,Chandler Arizona

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Earlextech

1159 posts in 2158 days


#6 posted 02-08-2012 10:00 PM

It’s important to spray a “wet” coat.
After spraying, if you think, “Oh well that will flow together”, wrong, it will not, the coat is not wet enough. If after spraying you can see a puddle or runs then it is too wet. The only way to know what is right is through experience and practice.
Also, you should add a retarder or flow agent to the mixture, about an ounce per quart should do. This will extend the drying time and will eliminate the orange peel.

-- Sam Hamory - The project is never finished until its "Finished"!

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404 - Not Found

2544 posts in 2437 days


#7 posted 02-08-2012 10:12 PM

Hi Sunny,

I’m using the Fuji Mini-Mite system – 3 stage turbine and XT gun. I haven’t tried waterbased polyurethane, I looked at all the waterborne finishes and the one that ticked all the boxes for me was Becker-Acroma WB Lacquer. Made for spray application on furniture, trade rated and readily available.
I have had orange peel at one time or another too, usually because of stupid things:-
just moving the gun too slowly and putting too much on etc
when the air cap/nozzle has been slightly blocked, the spray doesn’t atomise like it should and spits it out,
putting the turbine on the jointer instead of the floor – the heat from the turbine softening the hose and making it droop, reducing the airflow

I’d really like to know if your test samples are getting runs in them when sprayed upright, this would show if your flow is too high

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