General Finish High Performance thickness

[Tom DiBiasio]

First time sprayer here - and I have a question regarding high performance coat thickness. I have been spraying countless numbers of card board boxes and finally decided to shoot my first coat of finish on my table project. As an over abundance of caution I decided to spray a very thin first coat. As an additional test while I had the gun full of HP, I sprayed a practice board left over from same project wood and this time I slowed down significantly my stroke, to the point I was getting a wet blue haze behind the gun. I let the test board dry and to my surprise it leveled out great and the sheen was more pronounced then the project table. So my question is - When you spray GF HP is it best to move fast enough to not see the blue haze or is a thicker coat showing the haze what you try for? for reference I am spraying with an earlex 5500 and a 1.5 needle combo.

i also tries spraying a coat of zinsser seal coat that turned out to be very challenging to not get orange peel. I measure the viscosity of the seal coat with the supplied cup and it emptied in approximately 35 seconds. Do you think with material this thin that I should get the 1.0 needle set instead to spray this shellac than with the 1.5 set?? I am trying to work out a procedure were I can put a sealer coat over BLO before shooting 3-4 GF HP top coat layers.

Thanks in advance for any help you can offer...

TomD

[John TenEyck]

If you are seeing blue it's too thick. It will never cling w/o running or sagging on a vertical surface, and 4 coats that thick will not look good. I've never measured it but I would guess I spray about 3-4 mils wet thickness. The thing about WB finishes is you want the sprayed coat to look not quite continuous just after spraying. In a a couple of minutes, however, it will flow out into a nice uniform film with no holes. Practice, you'll get the hang of it. Buy yourself a wet mil gage if you think it will help; they only cost a few $'s.

I think you need the 1.0 mm N/N for Sealcoat. All you can do with the 1.5 mm N/N is speed up your pass over the work and/or dilute it with some DNA or a slower evaporating alcohol. That might help but the smaller N/N is likely the better answer. You only want a light coat of Sealcoat under HP Poly; just enough to form the thinnest film.

FYI, as nice as HP Poly is it's not very durable, despite what GF says on their literature. I wish it was because it looks great and is dead simple to spray - once you get up the learning curve. I hope your table is a side table, etc., something that won't get drink glasses set on it, or hot dishes. GF's Enduro Clear Poly is nearly the same as HP Poly in how it looks and sprays, but is a lot more chemically durable. EnduroVar is even more durable, on par with most solvent based varnishes, but is not as easy to spray.

John

[Marty Schlosser]

Whenever spraying any finish for the first time, I always measure the thickness of the coat by using a wet mil thickness gauge. That way I can measure exactly how thick I've laid it on. Read the finish manufacturer's recommendation as to their recommended thickness (usually 2 - 5 mils for the family of finish you're using... but try to find out what the manufacturer is recommending. It's usually available on their website) and see how thick you're laying each coat down, right after you've sprayed that coat.

John's right about blue being waayyyy too thick!

[Rob Young]

Quick browse of the GFHP data sheet does not show a recommended mil thickness. However if the OP calls GF, they may supply a range.

[Gary Muto]

....The thing about WB finishes is you want the sprayed coat to look not quite continuous just after spraying. In a a couple of minutes, however, it will flow out into a nice uniform film with no holes. Practice, you'll get the hang of it....


John

Great advice! I had to learn that the hard way. I live in CO so finishes dry quickly here which only makes things worse.. or different. I use 10-15% extender and find it easier to get a nice coat. I'm not very good at spraying and the extender made a big difference for me.

[John TenEyck]

That's a good point, Gary. Extender can be a big help for folks during periods of low RH.

John