Reading a furniture joint
FORM
Paint hides grain and it hides tool marks, but it rarely hides a joint. Three joints, and what each one tells you about how a piece was put together.
PLATE 08
A dovetail, a mortise and tenon and a dowelled rail, drawn as they read through a paint film.
Paint conceals grain, filler, tool marks and repairs. It very rarely conceals a joint, because a joint is a change of direction in the timber and a painted film follows the shape it is given. The three joints drawn above are the ones worth learning to see.
Dovetails
A dovetailed drawer shows its joint at the side, as an alternating run of pins and tails. Under paint the joint line usually remains as a faint ridge or as a hairline where the film has cracked along the seam with seasonal movement. Wide, irregular tails cut by hand and narrow, perfectly even tails cut by machine both survive under paint and both stay readable.
Mortise and tenon
A frame joint shows as a fine line where the rail meets the stile, and often as a pair of small circles where pegs were driven through. Painted over, the pegs remain as slight discs of different absorbency; in raking light they are usually still visible. A frame that shows no line at all at the junction has either been filled or is not a frame joint.
Dowels
Dowelled construction leaves the least evidence at the face and the most at the end grain. Where a dowelled rail has shrunk away from its stile, the gap opens evenly along the whole junction rather than at one end, which is a useful way of telling a dowelled joint from a loose tenon.
Why it matters under paint
The practical value is in deciding what a piece can take. A pegged frame joint will survive being stripped, reglued and repainted. A dowelled joint that has already opened will usually need the dowels replaced rather than reglued, and no amount of surface work will address it. Reading the joints first prevents a good painted finish from being applied over a frame that is coming apart.