Difference Between Spar Varnish and Regular Varnish? - Question of the Week
This week’s question comes from K Sanchez who writes: “Please tell me the difference between spar varnish and regular varnish?”
Now some of you may have noticed that I posted this question while I was on the road last week. An inquiry from reader Kip made me realize that I did a pretty crappy job of giving the level of detail required to answer this question accurately. So, here is a modified answer to the original question:
All varnish contains a few basic components: oil, resin, and a solvent. By modifying the type and amount of oil and resin, we can get a bunch of formulations for both indoor and outdoor use. Our oil options include linseed oil, tung oil, and other less expensive synthetic oils. Common resins include alkyd, phenolic and polyurethane.
So before we dig deeper, let’s talk about why we need a different varnish for outdoor applications. Any wood stored outside is going to be exposed to a wide range of temperatures and weather, as well as a good dose of damaging UV rays. The changes in humidity cause the wood to expand and contract, and a standard indoor finish would simply crack and deteriorate under these conditions. Spar varnishes are typically designed to give us general protection, flexibility, and UV protection.
The ratio of oil to resin has a dramatic effect on the way the varnish will behave. For instance, using a small amount of oil and a large amount of resin will produce a very hard and brittle finish. Obviously, this is not suitable for outdoor applications. So what makes more sense is to create what is known as a “long-oil varnish”, that is, a formulation that contains a greater percentage of oil. The extra oil results in a softer, more flexible finish. And from what I’ve seen, tung oil is generally considered to be the best oil for these outdoor applications.
As far as the resins go, it seems to be a mixed bag when it comes to spar varnish. While many articles claim that phenolic resins are the best and most common, I found that alkyd resins tend to be prominent as well. Both Helmsman Spar Urethane and Epifanes contain alkyd resins. Its interesting to note that they also both contain some urethane resins to “fortify” the finish.
Most spar/marine varnishes will contain other important additives such as UV blockers, that give the wood that extra bit of protection it needs in harsh conditions. So generally-speaking, my preferred outdoor varnish would be a long-oil varnish containing tung oil, alkyd or phenolic resins, and UV inhibitors.
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Thanks for the very detailed response, compacted into just a few paragraphs. Really taking the mystery out of it all.
Hi Marc,
I looked up “Epifanes” on the net and found out it’s a manufacturer’s name that makes several coating products. When you mention Epifanes which product are you referring to? I think I’ve narrowed it down to two: Epifanes Clear Varnish or Epifanes Woodfinish Gloss/Matte. (Jamestown Distributors carries both products so that didn’t help me reduce the possibilities.)
The product I use is Epifanes Clear Varnish.
Good info, Marc.
Now, when are you going to post video from your David Marks visit? :-)
haha. unfortunately, I think you are going to have to wait quite a while for that.
Well, major bummer. Since DIY stopped showing “Wood Works”, I’m really going to be missing DJ Marks.
Stopped showing Woodworks?!?!? Have they gone mad??!?!?
I like David Marks stuff as much as anything I’ve seen but Woodworks has been in reruns for how many years now. I don’t know about everybody else but I get tired of watching him build the same thing over an over. I actually took it off my to do list on my dvr and then after a year or more put it back on and it was still just reruns. I just think that he didn’t want to continue with the show and moved on to different things. Claude
Oh and Marc, Leo Laporte is doing the the Gadget station on The Daily GizWiz today on turn the table tuesday. Claude
They’ve really cut back their woodworking content over the past couple of weeks. Until recently the DVR would pick up usually 4-5 episodes of both New Yankee Workshop and Woodworks, granted they were the same episodes over and over a lot of the time, but now there’s one ep of NYW a week, no Woodworks at all. Of course you can still see “Hammered” with Jimmy and John DiResta, which is horrible. I’ve only managed to make it through two episodes before I gave up on that one. It was the beginning of the end for me when I saw one of them clamp a router upside down in a vise and use it like a table mounted router. Shudder…
One of my local PBS stations has started running The Woodsmith Shop but them, and Scott Phillips’ show (Pocket screws and Gorilla Glue! Yay!) are a poor substitute and the other PBS station is re-running Norm’s endless kitchen cabinet series right now. Bleah.
I stopped watching a long time ago because I had seen all the episodes so I totally understand. But there are lots of new woodworkers out there who haven’t seen all the episodes. And having WoodWorks on there at least gave people an opportunity to see some quality woodworking programming. From the sounds of it, there’s nothing left….. Very sad.
Good post!
A note on spar: Bob Flexner has stated several times that household spar varnishes typically have very little in the way of UV inhibitors. Manufacturers will typically just a few drops of the inhibitors to a vat of finish. And so their resistance to UV is not much better than regular varnish.
Marine varnishes, which are far more expensive, do contain considerable amounts of UV inhibitors. So if you need UV protection, you might want to head to boat shop….
Chris
As I understand it, the Epiphanes Marc recommended is in fact a marine varnish. Am I correct on this?
As for woodworking shows, I’m a relatively new woodworker and I learn something every time I watch Wood Works and New Yankee Workshop. Each show presents different styles and techniques, which I lke.
All the other DIY shows make me feel like I’m a “Master Carpenter”. ;-)
That’s correct Germain. Epifanes is a high quality marine varnish. My personal favorite for outdoor applications.
Folks,
A favorite subject since I have a boat and a home, both with brightwork and natural wood trim that gets hammered in intense sun. I re-coat it with spar varnish every 6-8 months. I seem to get a longer lasting application if I put a bit of stain in the spar varnish, as well as a bit of Penetrol. But the re-finish time comes around pretty fast.
I had a friend years ago that used what I supposed was a clear linear polyurethane wood ‘varnish’ on his boat’s brightwork, and he claimed it was a 10 year coating. I lost track of him and never have been able to find out what product he used.
I have also had people recommend Sikins (sp?) which I think is an oil, not a varnish, and might require stripping all the old finish off. Also it is used mostly on siding, and may not be a good product on brightwork that must resist abrasion and get reasonably hard within a couple of days..
Maybe we could all benefit from re-finding out what the best long-life product might be.
Great site, by the way!
Thanks,
Richard
David “retired” from PBS in 2001 so all shows are reruns.
Norm had a new series on kitchen cabinets recently that has a lot of good stuff, otherwise his shows are also reruns
but all these shows have something worthwhile for the new and not so new woodworker IMHO
Richard
I want to put finish on an old pine floor that as never had a finish on it, but would like it to be durable as far as not scratching etc. I have a formula that would consist of equal parts of boiled linseed oil,good turpentine,and gloss varnish. Would this be something you would recommend over a polyurethane?
Hi Jeanie. I am curious why this is going over a polyurethane. You said the door doesn’t have a finish on it yet. If that’s the case, I would just start applying your oil/varnish blend. Now if for some reason there is already poly on the door, the oil/varnish blend might not be the best option, because the wood is already sealed. Once that happens, the oil in your oil/varnish mix tends to stay tacky forever. So if you are coating over top of poly, I would sand the surface thoroughly to rough it up, then apply coats of the varnish/turp mix (no oil).
Thank you very much for your response. I am sorry that I did not make myself very clear. The oil varnish formula would be going on a floor that has never had a finish on it. My question is would this be better to use verses a polyurethane finish? This is a very old pine floor, and I would like a finish that would be durable to scratching etc. Thanks, Jeanie
Ahh, i see now. I also realize that I mistook “floor” and “door”, lol. My brain has been in another place this week with the website changes. Anyway.
The polyurethane would definitely be the best choice for the floor. Oil/varnish blends are nice one furniture and medium to low-wear projects. But the oil content in the mix results in a finish that is a little softer and doesn’t quite build as quickly or as thick as you would want on a floor. So without a doubt, I would recommend a full-strength polyurethane.
Hi WoodWhisperer,
My question is about coating my bay window sill. I used a recommended varathane I think it was called and after a year the plants my wife put on the sill have left a bit of a mark. I even put the plastic spill catcher under them, but I think there must have been some spillage that went unnoticed. I was going to sand it as best I could and re-apply a better product to save it from the same fate. I was going to put down a marine varnish to keep the water from damaging it again. Any recommendations?
Hey Alex. My favorite marine varnish is Epifanes. Probably a good option for your application. But keep in mind, no finish will withstand repeat exposure to moisture like that. The real solution is to protect the surface with some kind of barrier to the moisture, like a coaster on a coffee table.