Caulk Is Cheap Insurance
The step that gets missed most often in painting wooden windows is the caulking. Because the joinery on modern wood windows is almost as complex on the exterior as it is on the interior, both sides should be caulked with the same care. On the interior, you caulk mainly for looks; on the exterior, you caulk mainly for protection. For both, I use White Lightning (White Lightning Products, 800/241-5295, www.wlcaulk.com), a 100 percent acrylic caulk with a 40-year warranty.
I first carefully caulk each joint and seam where water can get into the trim and gain access to unprimed surfaces. Then I look for any horizontal surfaces that lack the proper slope for draining water. On these, I use caulk to build a little fillet between the horizontal and vertical sections to drain water away. Water wicked up by the end grain in these joints is one of the most common causes of failure.
In most cases, it's enough just to fill in any acute angles and slope the water to the edge of the sill. In extreme cases, where the sills are so rotted they need replacing, I'll shape the new sill correctly so that it will drain — but I still caulk it very thoroughly. (Fortunately, we have a carpenter on our crew, because we replace a lot of rotten sills.)
And in cases where windows lack proper head flashing, I'll gob caulk into the gap between window and siding (sometimes an entire tube's worth), again forming a fillet to act as flashing.
Finally, I run a bead of caulk around the glass pane, just where glazing compound would traditionally be. I apply a steady 1/8-inch bead, then smear it slightly with the edge of my dampened little finger. When done right, the caulk bead can't be seen from inside; but without it, there's nothing to prevent water from running down the glass and behind the wood trim holding the glass in place. Many windows come from the manufacturer with a bead of adhesive extruded into this gap. Because this adhesive quickly weathers away and leaves a channel where the water can sit, on new windows I remove the extra adhesive with a razor blade before running the caulk line. All of this is especially important along the bottom of the pane, where water constantly runs down and into the joint.
Painting the Windows
The windows are now ready for painting. Usually, I paint siding and windows at the same time, in which case I use spray equipment. But if I'm doing just the windows, I break out my short-handled 3 1/2-inch angled sash brush. A good latex brush has synthetic bristles that are much softer than those of natural-bristled oil brushes, which makes it easier to lay out the paint.
I paint windows from the center out and from the top down. Starting at the top, I first paint the glazing compound moldings surrounding the panes, then work outward toward the frame. I dip 1 1/2 inches of the bristles into the paint and clean one side off on the lip of the can. The clean side of the brush goes on the glass side of the sash, allowing me to draw a perfectly straight line along my caulk/glaze line. The paint should just barely lap onto the glass, just as if you were painting a traditionally glazed window.
Spraying paint. Compared with brushing, it may seem that masking a houseful of windows in order to spray-paint them is a lot of extra work. But I can mask an average 35-window house in less than one day and spray it in four hours — a savings of days over traditional brushing. Plus, it's easier to hire and train a good masker than it is a good hand-painter. And by spraying latex paint rather than brushing it, I can get a thicker, brushstroke-free finish.
To mask, I use a 3M dual-tack tape dispenser (3M, 888/364-3577, www.3m.com), laying tape on the glass 1/64 to 1/32 inch inside my caulk/glaze line. This slight gap allows some paint to lap past the caulk just onto the glass, creating a further seal against water getting behind the caulk. Then I lay a piece of 0.31-mil painter's plastic on the tape and trim it to size with a razor blade. If the window is unprimed and removed from the frame, I do the same to the inside glass, so that I can spray both sides of the window.
If I'm working on new unprimed windows or completely reconditioning older windows, I'll remove the sash from their frames and lay them flat on short painter's horses to prime the exterior side and the edges. When they're dry, I flip them and prime the interior. This way, any blemishes from sitting on the horses will end up on the exterior. I like to use Sherwin-Williams' A-100 latex primer for the edges and exterior, and a sandable, fast-drying alkyd primer for the interior (where flexibility isn't as crucial). I shoot all of my trim using a 213 reversible tip and the lightest possible pressure that will give me an even fan without "fingering" — those stripes you see from a poorly adjusted sprayer or a worn tip.
For the finish coat, I use Sherwin-Williams' new Duration satin latex. One coat goes on and dries twice as thick as SuperPaint, the paint it replaced at the top of the company's product line. (Some homes I painted with SuperPaint still look great after 20 years.) Plus, Duration has a lifetime warranty.
I first spray around the window's edges and let them dry. If the windows are new, I'll paint the interiors, then thoroughly caulk and reinstall the window so that I can spray the face and frame together. Duration is thick, so I try to use vertical strokes and avoid crossing horizontal and vertical passes; I spray carefully, using quick, light passes. On a complex piece like a 15-pane French door, for instance, I'll spray the entire door with overlapping vertical strokes, changing the angle of the gun slightly to get the top and bottom of the muntins and the left and right sides of the mullions.
I prefer to spray two light coats rather than risk runs. Over the years, I've found that there's no advantage to back-brushing smooth surfaces, especially prepainted ones. Besides, brush strokes won't level out completely with the new latex paints.
After 20 minutes or so, I check each window in case any sags have developed that need brushing out. If I spray carefully, runs will be rare, but if I find more than a few, it means that I need to go lighter with the spray gun. After all, with the windows already masked, a second coat of paint is a piece of cake.
If I'm spraying the siding, too, the windows should be dry enough to mask over after about 24 hours in warm weather. I lay 3M 2040 1 1/2-inch yellow masking tape flat around the face of the window frame and flush to its edge, burnishing the outside edge down and leaving the inside edge unburnished. Then I tuck plastic under the loose edge and trim it to fit with a razor blade. (I've found that yellow dual-tack tape doesn't hold as well for extended periods in this application.) Then the siding can be sprayed with abandon. Again, it takes less than a day to spray a typical 3,500-square-foot house.Jon Tobeyis a painting contractor in Monroe, Wash.