Frustrated first-timer has questions about using spar urethane

[SierraTrout]

Hello. I am refinishing a 30-year old solid wood entryway door which was previously stained, not painted. I am currently working on the indoor-side where the stain was still in excellent condition but the topcoat needed to be redone. I am using Varathane Spar Urethane, Oil-Based, in Semi-Gloss (I chose a spar urethane because I’ll also be refinishing the outer side of the door). I sanded the indoor-side with a fine grit. With the door lying flat, I applied the first thin coat using a high quality natural brush and with the product diluted to 50% urethane/50% mineral spirits. Right away I noticed that some areas were dull while others were shiny. I don’t know whether it’s because I applied the finish unevenly; whether some areas “absorbed” the varnish more than others; or whether the product is faulty. I stirred the varnish thoroughly before applying. Is this common for semi-gloss spar urethane? Will the shine be consistent all over after additional coats?
 
Another concern is drying time. The product container says that drying time between coats is 10-12 hours (and this is at full strength). I expected my first coat to dry faster as it was diluted 50-50. The weather daytime high was mid-80’s; the evening was low 60’s; humidity 40%.  At 12 hours the finish was slightly tacky. At 22 hours the finish was drier but not hard and smooth. I tried a fine grit on a small area and while the paper didn’t “gunk up,” the sanding wasn’t producing a fine powder nor a smooth surface, and it would be possible to scratch the surface with a fingernail. Am I doing something wrong or is this typical? Should the surface be hard and fairly smooth to the touch before applying additional coats? I have guests arriving in 9 days and the door needs to be back in place by then. At this drying rate, I don’t think it’s possible to get the interior and exterior sides done. I’m willing to consider switching products, if that’s what it’ll take, like possibly a water-based varnish. Or would it make sense to reinstall the door on its hinges (but without the other hardware) and continue to apply the finish using the wipe-on method so it can be done vertically? I know that method involves several additional coats but at least the guests can come in through the front door instead of through the garage. I would really, really appreciate your ideas and help.

[cputnam]

Spar varnishes are deliberately made soft so they flex on a boat. Varnishes with flatters added (semi-gloss) need to be stirred very often.

If the exterior side is going to see the sun and/or rain I'd go straight to SW A100 deep base tint. All the needed benefits of paint but it still dries clear.

[SierraTrout]

Curt, thanks for your reply and recommendation. When you say that spar varnish is meant to be soft, does that mean it won't feel smooth and sleek when properly applied and sanded between coats? Our front door is fairly recessed so the exterior side will never receive direct sunlight, and we live in California where the temps are mild. I'm wondering if a water-based poly would be sufficient? Again, thanks for your help.

[cputnam]

It's a matter of the UV blockers. Varnish apparently can not contain the levels of UV blockers that paint can. That said, the best exterior varnish is widely believed to be Ephinanes spar varnish. It's expensive and requires a minimum of 7 coats for the 1st course. I live in SoCal and the front has an eastern exposure. Front door handle heats up to the point where I cannot handle it in the AM. I've repainted once during that period - at 9 years. Sun also destroyed the paint on the garage door.

I know it goes against the grain but I would go paint for the exterior side. Take a piece of wood into the nearest SW store and ask them to put some A100 deep base tint on it. May solve the problem for you.

[fredhargis]

Curt nailed it. The exterior paint would be a much better choice. As for "poly", finishes with urethane resins never do well outdoors...they break down quickly in the UV exposure. Spar varnishes are called "long oil" varnishes; as mentioned this makes them softer and more flexible. All vanishes are a mixture of oil and resins (and other stuff) cooked together to form varnish. Long oil varnishes have more oil in the mix, that's what makes them spar varnishes. Here's more info on the paint angle,be aware the article is a little dated, oil based paint is getting harder and harder to find, unavailable in many areas. There are some other waterborne that many here have reported great success using, like GF's Exterior 450 (no experience with myself). But regardless of your choice, you most definitely want to skip that spar you have for the exterior surface.
[url=http://www.askhlm.com/Articles/ArticleViewPage/tabid/75/ArticleId/26/Paint-On-A-Clear-Finish.aspx][/url]

[SierraTrout]

Hi Curt - My original intent was to go with paint because of all the benefits you mention, but in the end I couldn't do it ... I couldn't cover up the beautiful grain and rich cherrywood finish. So many doors are fiberglass these days and I wanted to preserve what may be the last solid wood door in our neighborhood. But, alas, since my plans may be going south I may have to reconsider. Thanks for all the info.

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Hi Fred - Now that's two votes for exterior paint ... hmmm. Thanks for the detailed info on varnishes and I'll look into the products you mention. Back to the drawing board!

[fredhargis]

You do realize the untinted paint suggestion I made makes for a clear finish????? The untinted paint looks very much like varnish (at least the oil based ones do) and while any clear finish will need maintenance over time, these will minimize it.

[SierraTrout]

Fred - No, I didn't realize you were talking about a clear finish. I was thinking paint = tint. Sounds like the perfect solution. I'm heading to SW now to check it out. Thanks for setting this newbie straight.

Curt - I realize now that you did say the SW A100 deep base tint dries clear. My brain didn't register this at the time. Now I completely see where you're coming from. Thank you.

To both of you: I am always amazed at the willingness of complete strangers to help each other out. You are doing a great service and it's truly appreciated!

[fredhargis]

Don't forget the part that it has to be the deep base to be clear (sometimes called #4). The ones for lighter colors have some TIo2 in them, and won't dry clear.

[joe1086]

When you get to SW they likely will not have a clue that the deep tint base will dry clear. Buy it anyway despite what they say.

I've done exterior doors using this technique and it is way more effective than varnish.