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HVLP for varnish?

Submitted by Paul Harker on Sat, 03/31/2018 - 13:46

Anyone have tips regarding spraying varnish with a 3 stage turbine HVLP?

I have a FujiSpray with the large 1.8 aircap for high viscosity coatings such as varnish and am considering spraying my final coat. 

I'm using interlux schooner and would likely thin with VM&P Naptha.

Bob Ten Eyck

Sat, 03/31/2018 - 21:11

It should work .I have similar sprayer -I am going to try it on my next build. This was applied with a foam brush. The sprayer just requires so much clean upFoam brush

Mike Bielski

Sat, 03/31/2018 - 23:59

Drop a note or call the tech line for your manufacturer.  It's their job to know the answer and tell you about it!  Most companies have great people happy to help.  

m

Paul Harker

Mon, 04/02/2018 - 19:12

Interlux recommended a 1.4 mm nozzle thinned 5-10% with Interlux 216 Special Thinner. 

So that puts me at a 1.3 or 1.5 mm nozzle which are the closest sizes available for my gun.

FujiSpray, manufacturer of my spray system, suggested a 1.5 mm nozzle, thinned no more than 10%, and a Ford #4 viscosity time of 25 - 30 seconds. They were great, going so far as to research the actual paint rather than give me a generic answer.

Jeff Jewitt, author of several books and videos on spray finishing suggested a 1.3 nozzle and thinned 10% with VM&P Naptha.

I looked up the MSDS for the Interlux 216 thinner and discovered it to be 75-100% Xylene with the remainder Ethylbenzene. Bought the same stuff for $9 at the local hardware store.

Tomorrow I plan on spraying a coat on the hull using a 1.5mm nozzle and thinned per FujiSpray & Interlux. If I get orange peel I'll do the next coat trying the 1.3mm.

Based on several sources I'll warm the varnish slightly, and remove the air restrictor valve from the hose to ensure maximum possible pressure at the gun.

Fingers crossed.

Paul Harker

Tue, 04/03/2018 - 11:30

I just finished spraying the hull with mixed but promising results.  Two errors in my previous statements -- I had mis-remembered, and  I don't have a 1.5mm nozzle, so 1.3 it is. Also, my HVLP is four stage, not three.

I thinned to a 30-second viscosity measured using a #4 cup.  The varnish went on a bit thick (based on the amount of material left in the spray gun) and  I have a slight orange peel on the horizontal surfaces -- vertical surfaces were smooth. I believe the varnish needs to be thinned a bit more. I'll let it dry, wet sand, then give it another go. Only when I'm happy with spray finish on the hull will I dare attempt the more visible deck. 

Paul Harker

Wed, 04/04/2018 - 15:30

I thinned the varnish to a 20 second viscosity and it went down very smooth. Unfortunately I had a problem with my gun and ended up spraying too heavy on one side resulting in some sags/runs. So now I have to decide whether to live with them until the hull needs  maintenance, sand and recoat entire bottom, or wait a few weeks and sand/buff them out. I'm leaning towards the latter

Paul Harker

Mon, 04/09/2018 - 12:32

Thank you all for the kind comments. I'm pretty much a spray finishing newbie, so I doubt I did it even close to the best way, but it worked.

Finished Varnishing