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SPAR URETHANE FINISH WRINKLED BADLY

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Forum topic by deadoakcarvings posted 10-15-2014 03:17 AM 1793 views 0 times favorited 6 replies Add to Favorites Watch
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deadoakcarvings

15 posts in 1095 days


10-15-2014 03:17 AM

Topic tags/keywords: finish spar urethane wrinkle oak

Hi all,

I was making a nice oak bench, with a seat and a back from bookmatched slabs of 19” wide oak, and I was at the finishing stage. The first coat went on fine, as expected, but the next day when I sanded and applied the second coat, it wrinkled horribly across almost all of the surfaces by the time I applied the last of the finish!

I am guessing that it was some combination of not waiting long enough, humidity, temperature…..just not sure. I’ve been applying finish just like this for the last 5 years, in all weather conditions, and I’ve never had this happen.

I’m using Minwax Helmsman Spar Urethane, and applying with chip brushes.

Any help or advice you could give would be great, thanks.

Dave


6 replies so far

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pjones46

986 posts in 2104 days


#1 posted 10-15-2014 03:32 AM

For some background: Have you always used Minwax Helmsman Spar Urethane? Did you make sure the can was stirred before use? IF not did you read their directions closely for overcoat times etc? How old was the can of Minwax Helmsman Spar Urethane? Was it used previously? Had you thinned the can of Minwax Helmsman Spar Urethane and with what?

-- Respectfully, Paul

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deadoakcarvings

15 posts in 1095 days


#2 posted 10-15-2014 08:43 PM

I used to use Spar Varnish: three years ago I switched to Helmsman Spar Urethane and haven’t used anything else. I did stir the can, however there is one difference with this can. In an effort to try something new, I bought an Ace brand paint can lid with a pour spout. It never sealed right, and every time I opened the can, there was a film on top that I had to pull out and discard. Not sure if this may have altered the chemical composition of the Urethane, because it happened several times. The can is only a couple months old, one gallon in size. I never thin the urethane, mostly because no one ever showed me how, and I’m unsure about it. I did not read the wait times on the can this time because I usually recoat after 24 hours every single time. This time I did not have the wood stove going, so the temp was cooler, and the humidity seemed higher with all the fog and mist. I did try to sand the wrinkles out, and in one spot where I got aggressive, the top layer actually seemed to peel loose from the first coat. I am thinking I need to sand completely down to the first layer and start again. Just wondering if I should trash the 1/3 gallon I have left, or go ahead and use it again. Just don’t want to put more wasted time into a simple project.

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pjones46

986 posts in 2104 days


#3 posted 10-15-2014 09:23 PM

Trash the remaining. Buy new fresh product. I believe your original product is contaminated by air and moisture which causes the problem. Make sure can lid and can are cleaned before replacing can lid and neither are damaged from opening the can. When storing, you can use dry nitrogen and burp the can with it to force out air containing moisture. There are companies that sell airisol dry nitrogen for this purpose. Follow product directions for recoat instructions and temp of use.

-- Respectfully, Paul

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gfadvm

14940 posts in 2151 days


#4 posted 10-16-2014 12:03 AM

I have used MANY gallons of MinWax Spar Urethane (sprayed and wiped on). I learned very early that once it gets any ‘skim’ over it, it is a different creature so I won’t use any that has a skim on it. Not sure what changes chemically.

As far as recoat times, I have sprayed a second coat as soon as the first is tacky and had no problems with adhesion or curing. I spray it undiluted with a cheap HD gun.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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pjones46

986 posts in 2104 days


#5 posted 10-16-2014 12:37 AM

Urethanes inherently are reactive with atmospheric moisture, some worse than others. The longer the exposure, the more the original properties change. At one time I worked for a formulating company of Urethanes and this property change was a big problem. That’s how/why Gorilla Glue cures and over time turns to an unusable solid in the dispenser.

-- Respectfully, Paul

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deadoakcarvings

15 posts in 1095 days


#6 posted 10-16-2014 02:15 AM

great advice, thanks! I will have to postpone the re coat until tomorrow when I can get a new can. hopefully I will post pics soon…..

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