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Discussion Starter · #1 ·
Well I just got a new hvlp gun with hopes of easier finishing. I plan to use it for topcoat applications poly, varnish all that jazz. So when looking at the borgs I noticed that most all the cans say not for spraying... I was wondering what you guys use and how you thin it. I am very very new as in never attempted this with spray finishing before so all help is greatly appreciated.
 

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In my terminology poly and varnish are one and the same, and I've never sprayed it. But I have sprayed several other solvent based finishes and some waterbornes. They all say, in some way or another "do not thin", which is what you almost always have to do for spraying. That is due to the VOC regulations with which they all have to comply. So whatever you choose to spray, don't be too concerned with such warnings. As for what I use, NC lacquer is usually Watco, shellac is either Zinsser or I mix my own from flakes. Oil based paint is usually from a paint store (the box stores around me quit selling oil based paint) and waterborne paint is from the box stores. The only waterborne clear finish I've sprayed was Target Coatings EM 6000. One word about the waterbornes: thinning them can be tricky, it's best to get them ready to spray. I am looking forward to trying General Finishes HP waterborne, just haven't got around to it yet. A caution about spraying oil based finishes like varnish (and oil based paint): because it dries so slow, the overspray can settle and make a mess out of things in your shop. Be sure to have a way to contain it, keep the dust away, and deal with the fumes. You might also consider getting a copy of Jeff Jewitt's book Spray Finishing Made Simple, a lot of good tips in there.
 

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Discussion Starter · #3 ·
Thanks a lot some good tips in there and I may look into that book as I'm gettin an amazon order together anyway. Finishing is definitly my weakest suit in woodworkin.
 

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You will likely find oil based poly to be problematic to spray. Oil based finishes are slow drying so the over-spray is in the form of liquid mist droplets. They will float in the air and land on any surface in the area. Where it lands a crust of finish will form which is impossible to remove. Only spray oil based finishes outdoors or in an effective spray booth. Finishes that spray the best are waterborne, lacquer, and shellac.

Being new to spray finishing, let me suggest you buy Charrons Spray Finishing. Amazon will have it. It will give you the info you need to determine what equipment you need and how to set it up and, most importantly, how to adjust it to produce a good finish. The book will also tell you what you need to know about the techniques for spraying. You don't just pick up the gun and pull the trigger. With the proper info, you will get down the road faster and produce better looking finishes.
 

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Generally, when you spray a waterborne, you buy one that's already mixed for that. You can do a little thinning if needed, but doing too much can upset the chemistry (at least that's how I understand it). The Target Coatings product used was formulated for spraying, and I'm sure others are as well. Be aware, even though the waterbornes don't contain many of the hazardous chemicals that solvent based finishes do, you still need to wear a respirator with an organic vapor filter. Pick the one or two you are interested in, and then read the manufacturer's instructions...that would be the easiest way to pick one you can spray, or ask about a specific finish and spraying it here to get advice from those who have already tried that particular label.
 

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I recently started spraying lacquer. I love the fast curing and no sanding required between coats. In fact, most of the overspray droplets are dry before they land on other stuff. I am new to spraying and have gotten some great results with it. I can do several coats about 30 minutes apart which makes it quick to build 7 or 8 coats.

I have been using Deft brushing lacquer from the big box and thinning it about 50:50 with lacquer thinner. Of course, the can warns against thinning, but they have to since lacquer can be quite toxic to breathe.
 

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I use lacquer almost exclusively. At the beginning of the job I thin very little. Never more than 10%. Towards the end of the multiple coats I will progressively thin more and more until I reach about 50%.

George
 

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Good to know George. I like the first coat to be a seal coat, so I thin it to penetrate. And, as you know, I thin the last coats to get an even surface.
 

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Personally I think any finish is better sprayed. Some finishes are easier than others and some take better conditions or equipment but anything can be sprayed. I have sprayed oil based poly and since it is slow drying you have to be careful not to put too much on because it will run. I normally spray it at the end of the day and leave the shop so I don't stir up dust that might get into it. The easiest finish to spray is lacquer. You can spray it outdoors on a fairly windy day and have good results. It dries to touch so fast that you seldom get dust in the finish and there isn't the overspray problem. I can spray kitchen cabinets inside a furnished home without getting any more than dust on anything else. Latex paints are a little more difficult to spray. They are so thick you really need an airless sprayer or pressure pot to spray them. By the time you thin it down to use in a normal sprayer it is so thin it takes too many coats to cover. It makes it easier to use a brush or roller. Then you have the overspray problem to contend with.
 

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Steve, I completely agree about the lacquer. That is the only finish I've sprayed so far, and with all it's advantages, I don't see a compelling reason to try much else for top coating.
 

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So any tips on spraying/thinning the wayerborne. From my reading I think that's gonna be my route.
Lacquer used to be my go to finish until waterbased polyurethane came out. I've been using it since. It's very easy to spray, and is an easy clean up. It dries almost as fast as lacquer. You might try different brands as I have. I found that thinning any of them 5%-10% doesn't make much of a difference in the durability of the finish. If thinning my ratio isn't even an exact mix. It's about ½" of water or less in the bottom of a 1 qt cup.

I use several thin applications, and try to spray items vertically when possible. I don't puddle or let the finish pool. I suggest you use your gun with just plain water as a learning process to get a feel for air pressures to the gun and at the gun. Having a small air gauge and regulator right on the handle, will give you very accurate readings. I also suggest to the reg/gauge, use a disposable bulb filter.

Once you have practiced with air pressures, fluid control, pattern, distances from the subject, and speed of movement, you will have a much better understanding on what to do and how to make adjustments.






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Discussion Starter · #14 ·
Lacquer used to be my go to finish until waterbased polyurethane came out. I've been using it since. It's very easy to spray, and is an easy clean up. It dries almost as fast as lacquer. You might try different brands as I have. I found that thinning any of them 5%-10% doesn't make much of a difference in the durability of the finish. If thinning my ratio isn't even an exact mix. It's about ½" of water or less in the bottom of a 1 qt cup.

I use several thin applications, and try to spray items vertically when possible. I don't puddle or let the finish pool. I suggest you use your gun with just plain water as a learning process to get a feel for air pressures to the gun and at the gun. Having a small air gauge and regulator right on the handle, will give you very accurate readings. I also suggest to the reg/gauge, use a disposable bulb filter.

Once you have practiced with air pressures, fluid control, pattern, distances from the subject, and speed of movement, you will have a much better understanding on what to do and how to make adjustments.






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Thanks this was a very helpful post. So you thin the water base poly with regular old water?
 

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Thanks this was a very helpful post. So you thin the water base poly with regular old water?
Yep...regular old water. It can be new water.:laughing: I use just tap water. I haven't had a problem with that as there is some "expert" opinions on forums saying to use only distilled water. You'll find all kinds of advice on forums. I would say if you use regular old water and you later find plant growth or shrubbery growing from your finish, to start drinking bottled water, and change your mix water to bottled or distilled. If you are on your own pump/well water system and it's high in sulfur (actually hydrogen sulfide...and you can smell it) to use bottled water or distilled water.

You didn't state what compressor you have, as HVLP guns can have a high demand for CFM's. When experimenting with your gun, you can use ordinary cardboard as a test piece. I also suggest using as much light as possible on your spray area. HVLP output isn't that easy to see, and lotsa light makes it easier to see how wet your spray path and overlaps are. It's a matter of getting a glare on the work). You may have to set up some extra lighting if possible.






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My favorite is MLC's Klearvar conversion varnish. It's a 2 part acid catalyzed polyester lacquer. Awesome stuff.
 

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If you have a Sherwin Williams near you they will carry the different kinds of lacquer you might use. They have the Promar line of lacquers which work well in non-wet locations for medium to dark colored finishes. On lighter woods or where water is present you might use a pre-catalyzed lacquer. The Promar line is a nitrocellulose type lacquer which yellows as it ages and shows up on light woods. It is also less water resistant than the pre-catalyzed lacquer.

I think you would like finishing with either. It doesn't raise the grain and it dries fast and builds quick. With winter coming on you can even use it below freezing. It would just extend the drying time. The only drawback is humidity. The humidity levels really need to be below 70% or the moisture will get trapped in the finish and cause it to turn cloudy.
 
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