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Question for those who have sprayed Spar Urethane

PostPosted: Wed Apr 14, 2010 7:47 pm
by parnold
I have applied two coats of Spar Urethane with a brush.. and I'm planning on applying two more with my Iwata HVLP spray gun.

Any tips? Should I plan on more than two more coats?

Thanks in advance for any help.

PostPosted: Wed Apr 14, 2010 8:30 pm
by afreegreek
once you build a good film thickness with the brush/roller, one sprayed on coat will do.. you need to sand first with 320 to perfect the surface as any imperfection will be magnified by the next coat. best to thin it quite a bit too. this will help the surface to level without "orange peel" most finishes have a maximum recommended thickness of the coating. (usually on the can) anything more than this is not good.. thick coatings tend to crack over time as they shrink and dry out. spar varnish is a long oil finish meaning it is formulated to be elastic and move with the wood under it.. having excess thickness will make the finish less elastic.. less is better...

PostPosted: Wed Apr 14, 2010 8:34 pm
by parnold
Thanks!!

I was planning on using 320 grit paper. Hadn't thought about thinning it though, good idea there.

Here's to hoping it's not raining tomorrow night!

PostPosted: Wed Apr 14, 2010 8:39 pm
by Miriam C.
:thinking: wait till after the pollen is through coloring everything or...... :? I am itching to get at mine but the Oak strings are still hanging around.....What a mess that would be.

PostPosted: Wed Apr 14, 2010 8:41 pm
by parnold
Tree pollen hasn't really kicked in full here. That's part of the reason I'm working on the trailer at night when I get home from a 12 hour day.

PostPosted: Wed Apr 14, 2010 9:12 pm
by afreegreek
parnold wrote:Thanks!!

I was planning on using 320 grit paper. Hadn't thought about thinning it though, good idea there.

Here's to hoping it's not raining tomorrow night!


follow the directions for thinning.. most products shouldn't be thinned more than 10% but it depends on the product.. it should be on the can somewhere.. Spar Varnish is not the same as Spar Urethane (though they are designed for the same use).. and they will use different thinner..

you can use silicone carbide (black wet dry paper) and wet sand but it's not really the best thing.. open coat Aluminum Oxide is better.. and if you want a really spanky finish try one of these to block with.. I've tried them all and these blocks are the best by far.. maybe the best $15.00 you'll ever spend..

http://www.dura-block.com/durablockline.html

I have the whole set but you only need the 1/3 block.. it fits 1/4 sheet of paper

PostPosted: Wed Apr 14, 2010 9:21 pm
by parnold
That's funny, I sell Durablock at my warehouse, but was actually thinking something just a tad more flexible like Motorguards Softblock (SB-3).



Image

I think it will work better on the curve of the ceiling.

The stuff I am using is Helmsman Spar Urethane, I'll have to read the can to see what to thin it with and pick some of whatever it takes up at work tomorrow. It comes in handy working for the largest single location PBE Warehouse on the east coast.

PostPosted: Wed Apr 14, 2010 10:15 pm
by afreegreek
parnold wrote:That's funny, I sell Durablock at my warehouse, but was actually thinking something just a tad more flexible like Motorguards Softblock (SB-3).



Image

I think it will work better on the curve of the ceiling.

The stuff I am using is Helmsman Spar Urethane, I'll have to read the can to see what to thin it with and pick some of whatever it takes up at work tomorrow. It comes in handy working for the largest single location PBE Warehouse on the east coast.
cool, looks like you got the sanding block side covered.. I see so many people just fold a piece of paper and sand with their fingers and wonder why they can't get a good surface.. as far as I'm concerned, a good block is the most important finishing tool there is.

BTW, Dura Block has come out with curved sanding blocks.. they're new and I just got my set a while ago but haven't had a chance to use them yet.


*runs to the Motorguards site to have a look..