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 Post subject: Finish
PostPosted: Wed Jan 27, 2016 8:27 am 
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Location: Northern Maine and out of the city.
How do you experts finish a project using , lets say a spar urethane???
Some how I am getting little bubble spots? Should I thin with linseed oil? I used a foam brush??
Maybe be spray? I m doing a canoe so sags come into play. flat area then horizontal area.


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 Post subject: Re: Finish
PostPosted: Wed Jan 27, 2016 12:46 pm 
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Location: Seattle, WA, USA
Hey Ralph,

What is spar urethane? Spar varnish is hardening oil and aliphatic resins, urethane is a synthetic polymer. Have you got some type of hybrid finish?

Spar varnish is usually pretty thick even in the summer in Seattle. I can't imagine what it's like during a Maine winter. I usually thin the first two coats (of spar varnish) with mineral spirits, and then brush out the remaining coats very thinly, and always to a wet edge. Go slowly and let it flow out. You can't rush a good finish, take your time. I've always done spar varnish in the summer, but I have heard of folks keeping it warm in a water bath for winter applications.

If you're getting bubbles, don't shake it, stir it gently, and especially with a foam brush, don't wipe the brush on the side of the can. Only tip the brush with a small amount and brush it out thinly. Also, there are good foam brushes, and cheap ones. You definitely get what you pay for there.

Good luck,
Tom

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 Post subject: Re: Finish
PostPosted: Wed Jan 27, 2016 12:50 pm 
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Location: Hamilton, MS
little bear wrote:
How do you experts finish a project using , lets say a spar urethane???
Some how I am getting little bubble spots? Should I thin with linseed oil? I used a foam brush??
Maybe be spray? I m doing a canoe so sags come into play. flat area then horizontal area.


Never use a foam brush. Use a clean white rag - tshirt - wadded up to make a fist size wiping pad with a smooth surface (no wrinkles on the part that will contact the wood)). Dip it in the finish and let it soak up the finish you have in a separate container (not the one the finish came in) till it almost drips. Wipe in one direction, overlapping strokes. It should be thinned with either mineral spirits ( do not use linseed) if it's an oil finish, or if a shellac with denatured alcohol. Check the original container for what the mfg recommends for thinning. Some oil finishes recommend rubbing in the first coat to fill the wood pores (Formby's and other wipe on poly's). Several coats of thinned finish is better than one or 2 thick coats.

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Last edited by Gene on Wed Jan 27, 2016 8:33 pm, edited 1 time in total.

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 Post subject: Re: Finish
PostPosted: Wed Jan 27, 2016 8:03 pm 
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Hey Gene,

I think that you meant mineral "spirits", not mineral oil. Mineral oil will not dry or harden, and will only leave a gummy mess if combined with varnish. Mineral spirits will evaporate an allow the hardening oils in the varnish to polymerize.

Cheers,
Tom

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 Post subject: Re: Finish
PostPosted: Wed Jan 27, 2016 8:33 pm 
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tms wrote:
Hey Gene,

I think that you meant mineral "spirits", not mineral oil. Mineral oil will not dry or harden, and will only leave a gummy mess if combined with varnish. Mineral spirits will evaporate an allow the hardening oils in the varnish to polymerize.

Cheers,
Tom


Yeah I did. Sorry 'bout that. Fixed it, thanks. Sometimes my fingers have a mind of their own. :lol:

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 Post subject: Re: Finish
PostPosted: Fri Jan 29, 2016 8:08 am 
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Location: Northern Maine and out of the city.
Thanks guys.
I will try the rag deal I think


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 Post subject: Re: Finish
PostPosted: Fri Jan 29, 2016 9:40 am 
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Location: Northern Maine and out of the city.
Thanks guys.
I will try the rag deal I think


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 Post subject: Re: Finish
PostPosted: Sun Jan 31, 2016 8:07 am 
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[quote="tms"]Hey Ralph,

What is spar urethane? Spar varnish is hardening oil and aliphatic resins, urethane is a synthetic polymer. Have you got some type of hybrid finish?

Nope, alkyd resins, though still common in high-oil, UV-inhibited formulations called "Spar" varnishes, now have a more durable competitor. http://www.minwax.com/wood-products/cle ... r-urethane.

Natural bristle brush, flow, no return, maybe a bit warmer in the shop for flattening.


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 Post subject: Re: Finish
PostPosted: Sun Jan 31, 2016 11:49 am 
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Hey George,
Yes, you're right of course. Aliphatics are used in glue.
My mistake,
Tom

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 Post subject: Re: Finish
PostPosted: Mon Feb 01, 2016 6:53 am 
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Location: Northern Maine and out of the city.
Well its Monday morn and I am I the shop. I will rag on some finish today and see what happens. Last final coat I hope. If it fails I will buy a spray can of the same and shoot the old gal. I will snap a pic and post ASAP of the finish canoes. Four canoes in all. two 8 footers that will be turned into lights for a pool and tennis court area and the five foot canoes will also be used in the pool area I think?


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 Post subject: Re: Finish
PostPosted: Mon Feb 01, 2016 2:13 pm 
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Almost forgot. If it's bubbles, try a hair dryer to pop 'em by expanding hot air.


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