Cross Banding archive

Tuesday 16 September 2008

Paul Richardson reveals the art of crossbanding and stringing

Gallery

There are two techniques that transform veneering from a craft to an art. While both are often used to frame marquetry - where veneers are cut to form a picture or pattern - they are more dignified when used alone to make a plain surface more interesting, without interfering with its function.

Crossbanding

Crossbanding, happily, serves both a practical and an aesthetic function. It's practical purpose is to present a durable, end-grain edge around table tops, drawers and other parts which might be knocked or otherwise suffer damage in use. Not only is the end-grain of veneer much harder than its side grain edge but, if the worst happens and a piece lifts or is chipped at an edge, only a small, easily repaired flake is damaged, rather than a long sliver as would occur with side grain.

Aesthetically, crossbanding allows the maker to define areas with a crisp and elegant frame or border, controlling the viewer's perception to either increase the prominence of details - the perimeter of a drawer, perhaps, or a frieze below a cornice - or conceal them. By crossbanding the edge of a hinged table top, as with the sofa table featured elsewhere, the eye is encouraged to see the top as a whole, and is distracted from the join.

The degree to which this visual trickery operates can be controlled by the strength of the crossbanding's contrast with the main veneer. If we use the same material for both, the effect is quite subtle; if a lighter or darker toning veneer, for example walnut with mahogany, then a little more visual noise is introduced; if a full contrast such as satinwood with rosewood is chosen, the effect is either striking or startling according to the sensitivity with which it is used - it is easy to go too far.

Stringing

Stringing is the use of narrow strips, or lines, of veneer or inlay in the same way as crossbanding. When the thickness of veneer, stringing is applied along with the main veneer and crossbanding; used thicker, it is inlaid into a groove or rebate cut after the veneer has dried. This form may also be inlaid into solid wood.

Like crossbanding, stringing at the edge of a surface serves to protect the veneer from damage - the thicker, square lines may often be found running down the arrisses of a tapered leg, for example.

As a decorative device, stringing is used to define form, or provide a neat interface between crossbanding and main veneers.

Decorative stringing, made up of contrasting lines and sometimes crossbanding, is available commercially. A useful means of adding fine and complex decoration to a piece of furniture, like contrasting crossbanding, it is best used in moderation.

Preparation

Crossbanding is usually laid while the main veneer is still wet. The simplest form is used around the edge of a panel, table top or drawer front, often with a single line of stringing between it and the main veneer.

Prepare strips of crossbanding in advance, cutting it across the veneer leaves to a width slightly greater than will be needed - remembering to take into account the width of any stringing. As when preparing any veneers for laying with Scotch glue, sponge the leaves before cutting with scalding-hot water and press between two flat boards.

Cutting may be done in any number of ways - if the leaves are kept between pieces of plywood or MDF, then a bandsaw can be used, or each piece may be cut with a straight edge and knife, using a simple jig to maintain width and parallel. Probably the best way is to use a guillotine, as this should result in a clean-cut edge and will create no dust to interfere with adhesion.

Whichever method is chosen, stack the cut pieces together to retain moisture, and press them in a vice until they are needed.

Groundwork

Taking a small table top as an example, first lay the main veneer, overlapping the area to be crossbanded but not the edge of the groundwork. Now the main veneer is trimmed back to leave what is effectively a wide, shallow rebate into which the crossbanding and any stringing is fitted.

This trimming can be done with a knife and wooden straight edge, carefully measuring for width and parallel, or a cutting gauge set to the combined width of crossbanding and stringing can be used. This latter method is the quickest and, as speed is important when veneering with Scotch glue, should be used whenever possible.

Any shaped corner other than square - radiused, for example - can be cut with a template and knife.

Carefully lift away the waste and glue using a chisel, and the groundwork is ready for crossbanding.

Laying crossbanding

As usual, working quickly is the key to success with hand veneering, so make sure everything that you will need is readily to hand. Wipe the glue brush along one side of the table top - for a larger table, work on about 1000mm (39in) at a time - then press the stringing into place. Don't worry about fitting it exactly, as this will be done with the crossbanding, and allow an overlap at each end for later trimming.

Starting at one end, and leaving an overhang, lay the first piece of crossbanding in place. Wipe the glue brush quickly over it, then hammer down using the hammer diagonally, so that it pushes the banding into the stringing and main veneer. Avoid fierce hammering across the grain, as this will stretch the veneer leaving gaps when it shrinks back on drying.

Without standing back to admire the effect, lay the next piece of banding as quickly as possible, overlapping the first. Knife through both pieces to make the join, lift out the waste and hammer back down - if you have been slow, the glue may have gelled, but a quick touch with a hot glue brush should sort it out.

Repeat this process until one side is complete, with overhang at both ends. Now start the next side, laying the stringing and first piece of crossbanding, ovelapping the first side at the corner. With a sharp knife, cut through the lot to form a mitred join at the corner, then proceed along the side as before, working around the table top until it is complete.

The last mitre will be trickier, as the first side's veneer will have started to dry. Apply some hot glue to its surface to melt the glue holding it down, touching it briefly with a heated iron if absolutely necessary.

Shaped corners are approached slightly differently, in that crossbanding for the corners must be cut to fit from the same template as the main veneer, then laid. Likewise, bending the stringing around a tight radius can be tricky - practise first to see whether it is possible, and if not see below for details of routing square line inlay.

Stringing inlay

Line inlay is applied quite differently, and this method can also be used for composite lines, which tend to be thicker than a veneer, and indeed crossbanding when fitted to a solid wood piece.

First complete all groundwork, including any crossbanding, allow to dry and clean up as usual.

A groove or rebate is routed to take the line, which is then glued into it using PVA or similar. If fitted into a groove then the router cutter must be carefully matched to the line inlay to avoid a loose or over-tight fit; at these sizes, typically 1.6, 2.4 or 3.2mm (1/16, 3/32 or 1/8in) tolerances are close, so a test cut is advisable. Note also that most suitable glues contain water and will, therefore, swell the line during application.

Line fitted to an arris, or corner, is glued and then clamped into the rebate, which may be on a curve, with masking tape.

Cutting rebates and grooves of these sizes requires special care; in the case of grooves, the angle of rotation and low circumferal speed of these tiny cutters means that the groove can easily become choked with waste and to compound the problem, when routing into a previously veneered surface, the heat generated can melt the glue line.

To keep things clean, use a sharp two-flute cutter, plunging and advancing it slowly, proceeding no more than 75mm (3in) at a time then reversing the router back through the cut and forward again.

Cut the groove slightly shallower than the depth of the stringing, then run a line of PVA glue into it. Press the line gently into the groove with your fingers, then hammer it down - if the fit is correct it will be held in place without any clamping.

Cutting rebates for edge-fitted line can be done with any size of two-flute cutter - the danger here is tear-out, leaving a ragged edge. This will be much reduced by back-feeding the cutter.

Cleaning up

In the 18th century, veneered and inlaid work would be cleaned up entirely with the cabinet scraper. This is still the best tool for the job, and although the initial cleaning up can be done with a belt sander and a random orbital machine will finish-sand nicely, a sharp cabinet scraper will give the best results. This is especially true of contrasting timbers - rosewood sanding dust will embed itself into boxwood line, spoiling the effect, but a scraping action keeps the colours crisp.


Woodworkers Institute

Tagged In:

veneer , Paul Richardson , Crossbanding , Stringing , Inlaying

"In the 18th century, veneered and inlaid work would be cleaned up entirely with the cabinet-scraper"