By Gijs van Dorp
This is an early 19th century highback Windsor chair from the Thames Valley that I worked on in the second term. It has an elm seat, the legs and stretchers are cherry wood, and the spindles and back splat are made from birch. The bent armrest and back bow are ash wood. Several parts of the chair had suffered from woodworm infestation. The proper right (PR) stretcher had become detached from the front and back leg and the seat had a split running from the front to halfway the seat. Furthermore the PR crook shaped armstretcher and two spindles had previously been replaced and it had to be investigated whether these were appropriate replacements.
The treatment goal for this chair was to make it structurally sound and look used but well cared for.
The first part of the treatment comprised stabilizing the base, i.e. the legs and stretchers. Once the base is structurally sound the other parts of the chair can be taken care of.
The stretcher had failed where it was joined to the legs due to damage by woodworm activity. The lighter coloured areas indicate the loss of wood.
In order to prevent further loss of material and to reinforce the stretcher, it was consolidated with a synthetic resin. Consolidation in this case means filling the woodworm channels and cavities with a resin. A synthetic resin often used for consolidation of degraded wood is polyvinyl butyral (B 98) dissolved in industrial methylated spirits (IMS). A dilute (8% weight/volume in IMS) solution was applied with a brush onto the areas of loss. It is quickly absorbed by the wood and the woodworm channels. Eventually, the solvent evaporates and the wood retains the resin which forms a strong yet flexible material. Several applications were required to completely saturate the stretcher with the resin.
Detail of the stretcher after it has been consolidated. The resin film on the surface gives it a glossy appearance. A carbon fibre rod provides the necessary strength when it is being reglued to the leg.
I made two new spindles which replaced the two previous replacements because they were made from oak and did not match the colour and structure of the other spindles.
The new spindles were made from birch wood. I started with a square piece of wood and planed the edges until an (approximately) round shape was obtained. In order to be able to rotate the wood I used a MDF-board into which a V-shape groove was cut. The wood is placed in this V-shape groove and can be rotated to plane the edges. Alternatively I could have turned the spindles on a lathe. However, on the original spindles small facets were visible produced by the drawing knife when they were made. Therefore it was appropriate to apply a method which leaves similar marks.
The new spindles were glued with fish glue. Fish glue has a long open time which allows for making adjustments to the position of the spindles and the armrest. The right side of the armrest tended to bend outwards when it was not being supported by the two spindles. I used a belt-clamp to pull the armrest into its original position until the glue had set.
The spindles after colouring with oil colours.
A split in the underside of the armrest due to natural drying and shrinking of the wood is filled with a sliver of ash wood. Then the crook shaped armstretcher can be re-attached with a brass screw.
The arm stretcher is re-attached to the armrest. The fill was later coloured with oil colours.
I stabilized the break in the seat by gluing a patch of plywood elm onto the underside of the seat. This repair is non-interventive in the sense that no original material has to be removed. Furthermore it is easily removable in the future if necessary. Although the patch changes the appearance of the underside of the chair, it is inconspicuous when the chair is standing on the ground.
Finally the patch was stained with oil colours.