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Building a door out of salvaged spruce lumber
May 23, 2014
Part 3 — If you haven’t been following this series, the objective is to build a door out of salvaged lumber, in this case 2-by-4-inch and 2-by-6-inch spruce, using unconventional joinery. 
In Part 2, I discussed how to join the rails and stiles of the door together with #20 biscuits and #10 wood screws. Once glued, clamped and screwed together, the stiles and rails formed a strong door frame that will withstand the rigours of daily use. 
The door’s upper and lower panels are made of 2-by-4-inch lumber machined into 2 3/8-inch by half-inch laminates, joined together with #0 biscuits. 
When joining thin laminates, I glue them in two or three sections, depending on the width of the final panel. This method ensures that they do not bow during the clamping process. In this case, I joined one section comprised of three laminates and one section of four laminates. I used bar clamps spaced every eight-inches along the section being glued and Jorgensen wood clamps at both ends to keep the laminates flat. 
When gluing up, I tend to be liberal with the adhesive, preferring to see it squeeze out of the joints rather than risk a starved joint. I clean up excess glue with a rag soaked in water as soon as possible; otherwise, I waste much time and clog many sanding belts attempting to remove the dry adhesive. After 24-hours, I glue the two sections together using bar and Jorgensen clamps as mentioned to create a full-width panel.  
The completed panels and door frame should be final sanded with #120 grit belts or #120 garnet paper attached to a palm sander. 
Rotating/oscillating sanders are also acceptable for this job, but they can leave circular tracks in the wood, requiring a finish sanding with a palm, belt or block sander (block of wood with sandpaper) to remove them. 
Never sand wood beyond #120-grit as finer papers tend to polish the surface, making it difficult for varnish stains to fully penetrate and completely colour the wood. People cannot see sanding lines left by #120 paper unless you cross-sand, in which case the finest lines will be visible no matter how much stain you apply. 
I used a router with a carbide bit to create a 3/8-inch wide by one-inch deep rabbet on the back side of the door to hold the panels in place. As routers leave round corners, I had to square them with a chisel to match the panel’s corners. I ripped the completed panels to 16 3/8-inches wide, a quarter-inch less than the 16 5/8-inch openings in the door, to allow for seasonal movement. 
The panels are held in place by half-by-half-inch trim pieces mitred at the corner and secured to the door with #4 by one-inch countersunk screws driven through the edge of the trims into the rails and stiles. This technique leaves the panels free to float because no screws are driven directly into them; the trim holds them within the door frame.  
When fitting the trim, spend some extra time cutting tight, clean mitres so the finished job will look professional.  This can be accomplished with a mitre box and a back saw, an accurate table saw or a high quality chop saw. (Cheap machines are the bane of any woodworker as they cannot be fine tuned to produce accurate results.)  
My trim pieces stand slightly proud of the stiles and rails because I did not cut the rabbet sufficiently deep. I can leave them the way they are, deepen the rabbet or plane them down until they are flush with the door frame. Because I believe less is more (especially when it comes to work), I elected to leave them as they are.
Another advantage to screwing the trim in place is that the panels can be removed for final finishing, a procedure that can result in varnish build up in corners if the panels remain in the frame.  Moreover, if they are scratched or otherwise marred during daily use, they can be refinished more easily out of the door frame than in it. 
I rarely use wood stains because they can result in mottled finishes in which the stain penetrates the wood unevenly in different areas. Also, I’m a big fan of woods such as pine and spruce that age to a rich golden hue if left unstained.
I use white shellac as a sealer and clear urethane as a top coat to produce a silky smooth finish that can be wiped clean with a damp cloth.  White shellac can still be purchased from most lumber and hardware stores. (Don’t buy orange because it is intended for dark woods.) 
Shellac is the basic ingredient of French polish used for centuries by ebenistes, luthiers and other fine craftsmen. The solvent is methyl hydrate or denatured alcohol from which some people make their own windshield washer or door lock anti-freeze. 
As shellac is too thick straight from the can and will leave brush marks when it dries, I cut it with two parts methyl hydrate to one part shellac for sealing wood.  This mixture is runny, so watch carefully for edge runs as you work, brushing over them before they dry as they can be difficult to remove later on. 
I lay the door on a bench applying a first coat to the frame and edges, peeking under the frame occasionally to check for runs that have crept onto the backside. These can be removed with a rag soaked in methyl hydrate. I do the same to the panels.
As shellac dries quickly at room temperature, I flip the door frame and panels after two hours and apply a first coat to them. After an overnight drying period, I sand the shellac with #320 wet/dry paper. This produces a silky finish and a lot of white powder that must be removed with a tack cloth before a second coat is applied.  I work rapidly when applying  a second coat as brush marks will appear in the shellac if I continue to fuss over it. When all faces of the door frame and panels have two coats of shellac, I repeat the sanding process with #320-paper and remove the dust with a tack cloth. 
I let the shellac dry for about eight-hours before I brush on the first layer of urethane. (Oil-based or water-based products can be used over shellac.)  
I cut out-of-the-can, oil-based urethane at a ratio of one part paint thinner to two parts urethane to avoid brush marks in the final finish. Water-based urethanes require only a dollop of water to thin them sufficiently for brush work. 
Because it is easy to miss areas when applying a clear finish, I check for skips by shining a light over the wet varnish; then look directly across the surface on a horizontal plane. This simple technique will reveal areas that have been skipped. With a bit of fresh urethane on my brush, I feather skips into the surrounding area. 
I apply two coats of clear urethane, sanding in between with #400-paper and wiping down the surface with a tack cloth.  For a final coat, I use a semi-gloss that produces a gleaming, not glaring, finish when rubbed out with #0000 steel wool.  Use the steel wool until all surfaces look dull and flat. 
The final steps are to rub on a hard carnauba wax with a cloth; then polish the wax with a soft cloth or a hand-held electric buffer with a lamb’s wool pad. The result is a gorgeous, smooth finish with a lustre that cannot be duplicated by sprayed lacquers. 
It’s time to hang your handmade door.  I will discuss this in the next column, including some tips on how to square skewed rough and finished frames.