View Full Version : Clear, long term exterior finish [long]

Alan Mikkelsen
04-13-2005, 12:46 PM
I first saw this back in about 1998, lost track of it and just found it again. It puts forth an interesting concept that I've never seen anywhere else:

In a recent post my friend, Steve, made reference to my tests of doggie sprinkling on exterior finishes. I figure after almost a year of testing it is time to post some interesting discoveries.

As a preface, allow me to set the stage. Almost daily there is a posting about clear, exterior finishes for doors, chairs, signs and such. Responses run the gamut from diehard marine finishes to apply a coat of primer and then paint. Each of these has a bit of a problem. Marine finishes are not always the easiest to find and it grieves me to think of a lovely oak, teak, mahogany, fir, redwood or similar nice wood door painted in mauve goop.

Bob from Fl inspired me with his continuing and accurate statements about the failings of a clear coat and the advantages of a good quality exterior paint. I decided after lots of reflection that he really was right but there was always the picture of mauve in my mind. Sooooooooo, how could one take advantage of his advice and yet capitalize on the beauty of a nice wood.

I began to reflect on the characteristics of paint. Now, comes the boredom.
There were several things I knew about paint. Exterior paints contain a mildewcide and a fungicide that a varnish does not. The best quality paints will contain a UV protectorant and trans-oxide pigments in very high percentages. Almost all paint is custom mixed by the store. The retailer maintains a large supply of base products that are used to achieve the desired color. There are generally 4 base products and the specific one for your paint is determined by your color choice. These base products are either named or numbered. They are named pastel, deep, tint and neutral. If numbered it is cleverly 1, 2, 3 and 4 with the exception of Olympic who numbers 1, 2, 3 and 5. Olympic is unaware that 4 comes before 5. Pastel and/or 1 is virtually a pure white and used for the lightest of colors. The others are slightly color altered from white and more translucent than pastel. These are used for succeedingly deeper colors. All of this comes to neutral, 4 and/or 5. These are clear and used for the darkest colors. In the can they are somewhat opaque but dry more or less clear.
Now comes the testing. I bought 4 oak exterior doors. Each door was given one coat of the same MinWax Stain. On 3 of the doors, I applied 2 coats of "base" to the 6 sides of each door (3 coats on the top and bottom edges). Each of these three doors had a different type of exterior neutral, 4 or 5 base. The fourth door was finished with a consumer "spar" varnish from my local friendly paint/hardware store. The bases for the 3 painted doors were an exterior semi-gloss acrylic, an exterior semi-gloss oilbased polyurethane floor paint and a semi-gloss oilbased trim and siding paint.
The doors were set up, slightly inclined, in mostly direct sunlight under a pecan tree in the backyard. My wife just loved that one. Daily, the sprinklers managed to hit the doors. The birds in the pecan tree used the doors for target practice. And, yes, the dogs did anoint the doors on a regular basis. My blonde Cocker, Zazu, was particularly enamored with the doors. Over the course of the test the doors experienced lots of Texas sunlight, rain and snow. The temperature went from below freezing to over 100. The advantage to the inclined position of the doors was the snow, ice, water from the sprinklers and the rain tended to collect in the raised panel areas. I feel these doors were subjected to far more severe environmental conditions than would be expected from normal use.
The results were interesting. The "spar" varnish looked fabulous but after about 2 weeks it began to develop small cracks. In rapid order the door began to turn black, started to mold and the smell was enough to knock a buzzard off of a manure wagon. The waterbased acrylic is milky in the can like a waterbased poly. It dried to a more or less water clear surface but was a bit cloudy. It tended to wash out the stain a bit. Over time it became cloudier and ultimately become almost white. But, it remained solid and protected the wood. The oil based bases are also a bit opaque in the can but dried to a clear finish that is almost identical to a spar varnish - they added an amber tone to the doors. Both the poly floor paint and the trim and siding paint remained "clear" over the entire test period.

The testing came to an end with a bit of encouragement. My wife said something clever like, "Get those damned doors out of the backyard?". She does not understand science. The floor poly had some minor checking and a thinned coat of the same base over the surface made that disappear. The door with the oilbased trim and siding paint was perfect other than it had lost a bit of the gloss.

So, I am with Bob - paint the door. My preference is the oilbased products. If you are predisposed to a waterbased use an acrylic rather than latex.

One thing you will find when you go out shopping for your product is a lack of knowledge on the part of the salesperson. Not many of these folk are aware that their neutral or 4 base will dry clear. If you want to have some fun, spring it on them. They will suggest you are full of Donkey Dust. Ask them to shake a can and put some on a stir stick. Dry it and voila, it is clear.

Jim Kull

Alan Mikkelsen
04-13-2005, 1:00 PM
And here's another testimonial to the procedure......

My recollection is that Jim made this post back in July, 2002 (at least that is when I saved it on my computer). Prior to the complete explaination he would post bits of the same information. About a year and a month or two before this post (spring of '01) I was talking with Jim while driving to Virginia to assist my brother-in-law with some maintenance on their log home. One of the tasks on the schedule was to refinish their south facing, no overhang front door...again! It was at that time that Jim informed me of his "test". A couple of days later the door was stripped, sanded, and "painted" with Olympic brand exterior oil-based paint base #5. By my count that's coming up on five years.

Just before making this post I called my brother-in-law to see how the door is doing. The report is that the door looks as good as it did after we refinished it back in '01—it shows no signs of cracking, yellowing, or any of the other common traits of Helmsman Spar Urethane in a similar high sun exposure; the builder recomended finish of choice before Jim's advice. I have used a couple of other brands and find that all perform pretty much the same so long as you get the paint base used to mix the darkest colors. Testing, however, is always appropriate. I can also sympathize with lack of help you have received from your local S&W dealer. As soon as you explain to the typical paint store employee what you intend to do the reaction is generally
the same—"Oh, that won't work..." On one of my let's-have-some-fun-with-this-guy visits to a local Benjamin Moore dealer last summer I explained the concept to the salesman behind thecounter. He assured me with great certainty that I was completely wrong (I getting accostum to hearing that) and that what I proposed wouldn't work. I asked him to open a can of the appropriate base and just stick a wooden stir stick into the paint. When he withdrew the stick he showed me with great pride how cloudy and milky
it was. I told him to set it aside and I would return later. When I did his response hanged;
"OK, its clear; but, it still won't work—if you don't add the pigment the paint won't stick right" (his words).

So, off to Lowe's with you, get the #5 base and
have some fun


Alan Mikkelsen
04-13-2005, 3:42 PM
BTW, as I understand it, this must be an oil-base.