While working on a 19th Century bar back chair at West Dean, we uncovered an unusual piece of metal embedded in the centre of the chair leg. This piece of metal turned out to be part of a previous repair job - one that had lead to further damage later in the chair's life.
A Shattered Leg
When the chair arrived in the workshop, it had some minor surface damage, but most noticeably the front right leg was severely damaged at the top. It had several splits and cracks in the upper area near and around the internal joinery. An attempt had been made to glue and screw it back together with a PVAc adhesive and a long slotted screw (see photos below). The head of the screw was sawn off carelessly, leaving saw marks radiating outward from it on the side of the leg, and despite the screw being there, the timber hadn't entirely come together, leaving a 2mm gap which was filled with hardened and brittle adhesive.
I have seen this sort of thing a lot while running repair cafe's and working at The Bower Woodworks. I have mentioned in a previous post about repairing furniture with PVA glue that it is absolutely essential for the timber to have solid contact with no gaps for the join to be successful. What we see commonly is that the timber splits, glue is shoved into the gap, but the wood isn't clamped together properly, and a screw or some nails are added due to concerns that the glue won't hold. If the wood isn't clamped firmly together, you have the old oreo cookie situation, with timber, a thick was of adhesive, and then timber. PVAc can become brittle as it ages, and without anything added to improve gap filling properties, it is likely the adhesive will either crumble or if there is any flex or movement in the wood, it will come off of the timber.
The treatment proposed was to open the break, clean out all of the old adhesive that was preventing the pieces from meeting up properly, and adhere it back together. It was when we spread the timber apart that we found the weird object embedded inside the break.
Finding an Earlier Repair
At first the object looked like it might be plastic, but a small amount of scraping revealed it as some kind of metal, likely steal. It's shape at first look consisted of a broad cylinder with vertical grooves and a cone on the top which had a diameter roughly a third of the larger cylinder. Neither myself nor our Tutor, Norbert Gutowski, has any suggestions as to what it might be.
I was personally very confused by the object. Surely it wasn't in there before the leg broke. How would it have gotten there? How did it get there? Why would someone put such a strange shaped object inside of the break, putting so much work into embedding it cleanly, when the same work wasn't put into gluing the timber back together?
Further mechanical investigation revealed that the piece rotated slightly. On an instinct, I put a flat head screwdriver into one of the slots and tapped it gently with a hammer. The cylinder rotated further, and the leg below began to wobble. Continuing to rotate the cylinder showed it to actually be a nut at the end of a long double ended bolt that had been inserted during an earlier repair to fix a break slightly lower down in the leg.
Cause and Effect
What I can presume is that the leg broke in one of the hollows of the turning (thin bits near the top) at some point in the 1900's and it was repaired by an eager and somewhat clever person. The used the double ended bolt to provide newfound strength, not knowing or trusting of other potential techniques. They embedded the nuts for the bolt into the leg below and above the break (chiselling in and then covering the holes up with timber blocks). They then assembled the leg with the bolt and tightened the nuts with a screwdriver from the side (in the reverse to how I removed it).
This repair was very solid, and prevented that break from coming undone again despite continued use and impact. Unfortunately, because steel has a different toughness quality to timber, it directly caused the greater damage higher up in the leg. Steel has less give and flexibility than wood. Upon continued impact to the chair leg, the rod refused to flex, and the timber levered and split from the original break all the way vertically to the top of the leg.
This second break was the one that was unsuccessfully repaired with glue and a screw. In the end, I had to remove both repairs in order to secure the leg again.