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spraying varnish

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Forum topic by bygrace posted 03-07-2018 09:04 PM 901 views 0 times favorited 19 replies Add to Favorites Watch
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bygrace

181 posts in 2086 days


03-07-2018 09:04 PM

Topic tags/keywords: varnish

To make a little money to help buy new woodworking equipment, I build and sell farmhouse tables. I’ve recently upgraded my product to hardwood and wanted to start spaying varnish as the finish instead of lacquer. I’m using Behlens Rock Hard Tabletop varnish. I began with two coats of shellac as a sealer. I thinned down the first coat of varnish 1:1. It went on nice and smooth, no orange peel, but left lots of tiny bubbles that didn’t work their way out. I sanded and applied the second coat thinned down 2:1. Same result. temperature was about 70 degrees. I use an Earlex sprayer. Any ideas on how to avoid the nasty little bubbles?

-- Andy, Waxahachie, Tx.


19 replies so far

View Lazyman's profile

Lazyman

2386 posts in 1504 days


#1 posted 03-07-2018 11:26 PM

I have not used that varnish but a couple of quick searches yielded comments that it was not intended to be sprayed—only brushed on. In fact, one said that if you spray it you’ll get bubbles. Does the label say anything about spraying? Generally, if manufactures don’t have specific information on spraying, especially how much to thin it, then it is probably best not to.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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ArtMann

1043 posts in 933 days


#2 posted 03-08-2018 12:20 AM

Why are you doing all that thinning? I never thin varnish even 10% and I get good results.

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bygrace

181 posts in 2086 days


#3 posted 03-08-2018 01:26 AM

Nathan. instructions say to brush it on, but Ive sprayd on “brushing lacquer” before with good results so I thought I’d try it with this as well. Guess I was wrong, lol! I just need something that’s faster than brushing. My whole shop gets shut down when I’m finishing, so I need to do it as quickly as possible. I have brushed it on before, but with a 40” by 6’ table top, its hard to keep a wet edge – and I’ve got pretty quick hands. Is there a specific brand of varnish you’ve used formulated for spraying?

-- Andy, Waxahachie, Tx.

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bygrace

181 posts in 2086 days


#4 posted 03-08-2018 01:32 AM

Artmann – when I researched how to apply varnish a few years back, I read its a good idea to thin it 1:1 on the first coat when brushing it on, and then a little thicker as you go. Last time I brushed it on 3:1 for the last few coats worked pretty good for me. Since I was spraying this time I thought it might go on smoother if I followed the same guidelines. Are you spraying? What brand are you using?

-- Andy, Waxahachie, Tx.

View OSU55's profile

OSU55

1831 posts in 2106 days


#5 posted 03-08-2018 05:24 PM

Never usex the product but from the description Im surprised that with thinning it the bubbles get trapped – it has a long open time. What are you thinning with? If naptha, try ms. Perhaps the tyrbine gun is heating it and flashing the solvents but I wouldnt think so. Maybe surface contamination? A lot of sandpapers have a lube added that can mess with finishes. Prep some scrap sample boards the exact same way to test with. You will have to methodically work your way thru to find the source. Try brushing a test board, if it doesnt bubble that eliminates surface prep. The bubbles get trapped because there isnt time for them to pop, a function of film thickness, viscosity, and time.

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Jon Hobbs

147 posts in 821 days


#6 posted 03-08-2018 08:03 PM

I’ve had good results spraying General Finishes High Performance Water-Based Top Coat

It comes in different sheens.

-- Jon -- Just a Minnesota kid hanging out in Kansas

View UncleBuck's profile

UncleBuck

249 posts in 197 days


#7 posted 03-08-2018 08:12 PM

I have been using spar marine varnish for years it sprays good thru my hf gun i have to run it thru a paint filter and keep it stirred but had no problems so far just my 2 cents

-- Terry Uncle Buck Carvins "woodworking minus patience equals firewood "

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ArtMann

1043 posts in 933 days


#8 posted 03-08-2018 10:54 PM

I used to spray Minwax brand polyurethane varnish. Many people pan it but it works okay for me. I just thinned it until it would work in my Wagner conversion gun – maybe an ounce of mineral spirits per quart. I don’t spray much varnish on big things any more because I prefer lacquer. Due to its availability, I usually use Deft brushing lacquer. I have not brushed varnish in many, many years. Once I discovered the simplicity and fool proof nature of wipe on varnish, I never touched a brush again.

I make a lot of custom trivets and coasters to sell using my CNC router. I use Minwax polyurethane varnish in a rattle can for these items because it is too much work to clean up a spray gun for small lots of stuff like that. I have found this brand to be both heat and water resistant when sprayed with many coats.


Artmann – when I researched how to apply varnish a few years back, I read its a good idea to thin it 1:1 on the first coat when brushing it on, and then a little thicker as you go. Last time I brushed it on 3:1 for the last few coats worked pretty good for me. Since I was spraying this time I thought it might go on smoother if I followed the same guidelines. Are you spraying? What brand are you using?

- bygrace


View msinc's profile

msinc

497 posts in 620 days


#9 posted 03-09-2018 02:52 AM



I used to spray Minwax brand polyurethane varnish. Many people pan it but it works okay for me. I just thinned it until it would work in my Wagner conversion gun – maybe an ounce of mineral spirits per quart. I don t spray much varnish on big things any more because I prefer lacquer. Due to its availability, I usually use Deft brushing lacquer. I have not brushed varnish in many, many years. Once I discovered the simplicity and fool proof nature of wipe on varnish, I never touched a brush again.

I make a lot of custom trivets and coasters to sell using my CNC router. I use Minwax polyurethane varnish in a rattle can for these items because it is too much work to clean up a spray gun for small lots of stuff like that. I have found this brand to be both heat and water resistant when sprayed with many coats.
- ArtMann

I use the same thing and have had nothing but excellent results. Minwax Poly is very easy to use and drys fast compared to many other finishes. If I spray the satin finish it will sheen up if I put it on too thick. I also find that if you warm it up by running hot tap water on the can it will go on and wet out a lot smoother.
I have to ask, the OP is calling his finish “varnish”...what exactly is it? Is “varnish” an actual name of a type of finish? I always heard the word varnish used in a generic way to denote some type of clear satin or gloss finish on wood. Is there a real actual chemical called varnish {similar to lacquer} and if there is why would you use it over poly? I have also heard the term “shellac”....same thing or generic term for clear wood finish? Why use one over the other? I guess my biggest question would be is one any better than the rest?

View Sunstealer73's profile

Sunstealer73

169 posts in 2209 days


#10 posted 03-09-2018 03:13 PM

Why not just switch to a brand that is made for spraying? Seems simpler than trying to make one work that specifically recommends not spraying it?

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ArtMann

1043 posts in 933 days


#11 posted 03-10-2018 02:50 AM

As I understand it, Polyurethane is just one type of varnish resin. There are others, including Phenolic and Alkyd resin varnish.

View Jon Hobbs's profile

Jon Hobbs

147 posts in 821 days


#12 posted 03-12-2018 06:49 PM



I have also heard the term “shellac”....same thing or generic term for clear wood finish? Why use one over the other? I guess my biggest question would be is one any better than the rest?

- msinc

Shellac is a specific type of material. More info here.

-- Jon -- Just a Minnesota kid hanging out in Kansas

View ArtMann's profile

ArtMann

1043 posts in 933 days


#13 posted 03-12-2018 11:47 PM

Is there any particular reason why you are using shellac as an undercoat? In most cases, this is a needless step. What is it you are trying to seal in or out? The varnish will adhere to bare wood at least as well as shellac.

View Tennessee's profile

Tennessee

2880 posts in 2631 days


#14 posted 03-13-2018 12:17 PM

Agree with Art.
I refinished professionally for 12 years back in the 70’s and 80’s, and we never, ever put on a shellac undercoat.

Three coats of polyurethane semi-gloss varnish sprayed on was our go-to finish for about 70-80% of our work. Never had a problem. Back then, we were using the old suction can guns. Never thinned it. Buffed with 0000 wool two days later, carnuba wax finish, out the door. We could not keep up with the work.

The other things we sprayed was a two part epoxy varnish for things like kitchen tables and chairs, (always had to toss the gun afterwards although we saved a couple), and a mirror finish lacquer which was a very hard finish to get right with the shop we had. (Too much dust)

-- Tsunami Guitars and Custom Woodworking, Cleveland, TN

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bygrace

181 posts in 2086 days


#15 posted 03-13-2018 11:22 PM

msinc – I was using Behlens Rock Hard Tabletop Varnish. its says its a urethane varnish. I’m not using it over any poly, just the shellac which I used as a sanding sealer. Shellac can be used over or under just about anything and is very easy to use, but isn’t very durable. Ironically, I wanted to make sure there were no open cells, like oak has, that would release air bubbles into the varnish, so I put on two coats of shellac to seal it.

Sunstealer73 – I had heard that some of the labeling for finishes had changed to “brushing” because of environmental laws in California. Not stating this as a fact, just what I heard. Since It didn’t specifically say it wasn’t for spraying, and I have used this brand of Lacquer for spraying, I thought Id give it a try. guess I was wrong! Oh well, live and learn.

Artmann – please see my response to msinc above for my reason to use shellac first. I had brushed on some varnish a few years back on some oak and had a ‘bubble” problem I thought was from the open pores in the oak. Isnt it always a good idea to put on a sanding sealer? Please chime in with your thoughts to my comments below to Tennessee!

Tennessee – You may be the one I need to talk too! I wanted to step up my game with the farmhouse tables I’m selling, so instead of using pine and fir, I’m switching to alder, with oak and other hardwoods as an option. I also wanted to put on a better, tougher, finish so I switched from lacquer to varnish. Isnt varnish a tougher finish? Anyway, what brand of varnish would you recommend for spraying?

-- Andy, Waxahachie, Tx.

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