# Spar Varnish vs. Spar Urethane



## Brine (May 28, 2010)

I've recently read several posts here on how spar urethane is superior to spar varnish, and I thought I'd do my own research on the subject. Admittedly, just because I Googled the terms for an hour doesn't make my findings any more credible than taking someone's word for it, but I thought I'd offer up a few contradictory posts from folks who seem to know what they are talking about in an effort to let the new TinBoat modder have another angle on the subject, and possibly do his own research. 

What I learned in summary....

First, there is no regulation on what companies label their product. Therefore, the term "Spar Varnish" is not a stand alone recipe. 

Second, spar varnish is superior to spar urethane in UV protection and flexibility. Spar urethane is better at repelling water. Each have trade off's. It seems that urethane would be the natural choice as repelling water is most important;however, urethane does not hold up to uv protection (for those who have wood exposed to the sun) and is not flexible (like most wood decks will be when exposed to extreme temp changes and walking/putting load bearing weights on them) and thus fail by cracking, which then allows immediate water penetration. 

My hunch is that both could be the right solution for the right application in boats. 

Here are a couple general discussions on it:
https://www.boatdesign.net/forums/wooden-boat-building-restoration/urethane-vs-varnish-13461.html
https://www.woodanswers.com/expertadvice_cat.asp?row_id=5602&part=full

quote "Spar Urethane" varnish should be avoided in any exterior application in which even moderate exposure to direct sunlight is likely.
https://hardwoodlumberandmore.com/Finishing/MarineVarnish.html

quote "It's best to stay awary from urethane ingredients"
https://www.refinishfurniture.com/email_spar_varnish_or_tung_oil.htm 

quote "Alkyd spar varnishes are preferable to polyurethane spar varnishes because the alkyds tend to be less brittle than polys"
https://www.forums.woodnet.net/ubbt...al=&newertype=&olderval=&oldertype=&bodyprev=

I don't know that we have an authortative resource on the water sealer subject, but maybe this could be the "everything steelflex" posts for wood sealers.


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## perchin (May 28, 2010)

I've been using spar urathane over varnish for outdoor furniture for the last 5 years. Also so you guys know, because the kid at HD that is a self proclaimed pro. really don't know. The word spar vs. marine is of zero value becuase Spar = a mast, boom, gaff, or yard used to support rigging on a boat, so spar is marine. With that in mind both marine urathane and spar urathane are of the same value. Now a days there is no regulation in the name of finish. So that Spar Varnish may just be urathane and vise versa... :lol: clear as mud yet?


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## ober51 (May 28, 2010)

I used Cabot's Marine Spar Varnish last year when doing my deck (I thought it was reversed, originally). The decks are all covered in carpet, so I am hoping it lasts for several years, but we will see.


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## perchin (May 28, 2010)

ober51 said:


> I used Cabot's Marine Spar Varnish last year when doing my deck (I thought it was reversed, originally). The decks are all covered in carpet, so I am hoping it lasts for several years, but we will see.



I'm betting you will be fine. I think now after researching this more and calling my supplier today that company's are just using the word varnish as a general term. It used to be that varnish was made with linseed oils and such, which don't have protective values but more so to richen the appearance. According to woodcraft today, Varnish can be a multitude of ingrediants, including urathane.


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## bassboy1 (May 28, 2010)

Any varnish is better than no varnish at all....


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## ober51 (May 28, 2010)

bassboy1 said:


> Any varnish is better than no varnish at all....



Yeah, I would agree. I also used very fine steel wool in between all 4 coats of application.


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## rscottp (Nov 25, 2013)

Interesting article about it.
https://www.thewoodwhisperer.com/articles/difference-between-spar-varnish-and-regular-varnish/


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