Monday 9 July 2018
This article looks at techniques used for creating the style of American Arts and Crafts furniture, in particular from three of its most influential designers.
Frank Lloyd Wright was the most celebrated 20th-century American architect. His training was in engineering rather than architecture and the furniture he designed to equip his Prairie Style buildings reflected their functional geometric lines.
One signature motif of his furniture style was the square-section vertical spindles or slats he used for chair backs and bed ends, which we will look at in more detail.
Brothers Charles and Henry Greene took their influences from Oriental and Alpine wooden buildings. They applied contemporary construction methods and in the process came up with some ingenious solutions to cabinetmaking dilemmas, including prominent spline joints.
As well as manufacturing, Gustav Stickley published designs in The Craftsman magazine for others to make so his furniture was accessible to ordinary Americans. His vernacular designs applied the latest machinery to apparently traditional construction, emphasising large prominent joints including wedged tenons.
Frank Lloyd Wright, square spindles
One practical issue in making a closely spaced series of square-section spindles is that any inconsistency in dimensions will spoil the appearance. Minor differences in length create gaps between spindles and rails while differences in width or spacing stick out like a sore thumb.
Basic robust woodworking machines were becoming widespread in the later Arts and Crafts era and these were particularly good for accurate repetition. An accurately matched stack of square-section spindles, which would be labour-intensive and a test of skill with hand tools, can be easily planed, thicknessed and crosscut on machines.
While the machines are set up it is worthwhile making a few spares, typically 10 per cent depending on the timber quality, in case of rejects down the line.
American white oak is forested tall and straight so there is a large proportion of knot-free, straight-grained timber – more than is usually found in European sourced oak. It is harvested young, giving it a larger percentage of sapwood to heartwood which, being pale, is not always obvious before finishing.
Oak sapwood is traditionally discarded by European makers because of its reduced durability, high moisture content and mismatched colour, particularly if the oak is fumed. However, this practice causes a lot of wastage with American oak and an alternative is to include the sapwood and stain the finished furniture to a uniform colour.
The relative weakness of the sapwood will not cause problems in unstressed components like spindles and this is certainly a greener approach to using timber.
Joined in a row
There can be difficulty aligning all the spindles during assembly and glue-up. Assembling a row of two dozen spindles between rails is a bit like the circus trick of spinning plates – no sooner is one joint engaged than another one pops out.
Stub mortice-and-tenon joints on the spindle ends provide one option but their tight-fitting rigidity can actually make the assembly harder.
Dowels, although relatively weak, are adequate for joints in fine spindles. A big advantage of dowels is that you can stagger their heights during assembly so they engage one after another.
On wider spindles it may be possible to use a Domino jointer and make the socket marginally wider than the loose tenon. This allows the tenon to tilt in its socket while the glue is wet, easing assembly as the top rail is lowered onto the spindles from one end.
The rails are clamped to set the glue on the spindle joints before they are tenoned into the vertical posts. That way there is no risk of the post mortices holding the rails apart and creating gaps at the ends of the spindles.
Concave brackets are used to visually reinforce the right-angle joints between posts and rails. The biscuit jointer provides an ideal tool for applied decorative details like this.
Obviously an assembled row of closely-spaced spindles restricts access for final sanding and finishing so these operations should be completed as far as possible on the individual components beforehand. The final preparation then concentrates on the show faces.
Greene and Greene, breadboard tabletop
Breadboard ends have been widely used on tabletops over centuries because they address the problem of securing the board ends together as they attempt to swell and twist with seasonal movement. The crosswise rail also provides a long-grain end to the tabletop, so avoiding the checking and splintering associated with end grain.
The joint consists of a tongue or wide stub tenon on the end of each board, housed in a channel on the inside edge of the end rail. However, breadboard ends can themselves suffer problems with wood movement especially if they are locked by glue or a tight mechanical joint, while loose mechanical joints appear sloppy and unsightly.
The ingenious answer to these problems developed by the Greene brothers was to fit the breadboard end rail with a loose spline or tongue housed in a concealed channel in the end rail and a corresponding channel in the end of each board.
The joint was held together by a series of concealed screws through slotted holes in the end rail. Now the ends of the tabletop boards could expand and contract with moisture while still resisting any twist.
Square ebony plugs were used to cover the screw heads while the ends of the spline housings were plugged with an ebony spline. Rather than conceal the joinery details, the ebony emphasised them, but in a more appealing way than screw heads and open slots.
Making Greene breadboard
I used normal edge-jointing techniques on 25mm-thick American white oak boards, then clamped and glued them before crosscutting a matching end rail, approximately 3mm wider than the jointed boards on either side. I cut a 25mm-wide strip of 10mm-thick marine ply to make the spline.
With the glue set I routed housings on the end grain of the boards and the edge of the rail to make a snug fit in each for the ply. I continued the routing for 50mm either side of the housings to make the ebony spline a longer feature.
The screws used to secure the end rail are sunk in the base of a square socket cut with a hollow chisel morticer, or chopped out with a chisel.
The slots in the screw holes are made by drilling two adjacent holes then combining them with a tilted hand drill.
The spline end is shaped with plane and chisel to give it a stepped top, matching the step in width between the jointed boards and the over-width end rail.
I used old scraps of inherited ebony to make the plugs. Ebony is still available in small pieces but there are some arguably more environmentally friendly and cheaper synthetic alternatives such as ebonite. Alternatively a better substitute is to ebonise a fine-grained hardwood such as sycamore using black stain.
The square plugs can be pressed into place or glued if they are not tight enough. The spline end needs to accommodate movement without risk of dropping loose so I glued it into the housing on the edge of the tabletop board and waxed the end that was housed in the tabletop end rail.
Ideal for tabletops large and small, the Greene-style breadboard-constructed top is also good for cabinets, blanket chests or the tops of benches.
Gustav Stickley, through tenons
The through mortice-and-tenon joint was used by many Arts and Crafts practitioners and Stickley furniture features some particularly fine examples. Any through mortice-and-tenon joint needs extra care to avoid gaps in construction that would not show in a blind mortice, and wedged joints effectively combine two joints in one.
Making through mortice
To make sure a through mortice comes out clean on both sides without any breakout I chop it from both sides. This means marking out the joint carefully with a gauge and knife lines, then, using a square, running lines around the edge. They do not need to be full lines, just nicks on the corners will do.
Whatever your usual method of chopping a mortice – whether using a morticer, a router or a drill – it is best to finish the through-mortice by paring to the line with a wide chisel. This ensures the show side will have a flawlessly clean edge.
An Arts and Crafts feature that has strong practical benefits is the chamfered end on the through tenon. During assembly it prevents splintering at the exit hole of the mortice and in service it prevents the exposed tenon end itself from splintering.
Many Stickley designs used a removable wedge, such as for holding the rails in the posts of a demountable bed. The rounded top provides a lip for the wedge to be levered out. I used as a pattern the wedge from an old wooden moulding plane. It is angled at about 1:8 and I made it slightly concave to look more graceful.
Beeswax paste protects the finish, develops the colour and lubricates the joints, enabling them to be disassembled.