The Heartwood Arch: A Steam back in time. (Part 2)

The next half of the process involves the former or jig that you are gently persuading the steamed timber into. This is a negative space that is made up of two halves of jig-sawed MDF that allow for clamping together to initially form the shape of the steamed oak, and then forms the gluing jig that will hold the timber in place for the lamination process.

Ideally, it would be great to have a CNC (computer aided routing machine) to manufacture several jigs at once, to save on time; it generally takes 48 hours to form and glue one band of six bands that make up the arch! For this one, the whole construction of the arch took about three weeks including making the bases, using only one jig. We are looking to simplify this process down the track as demand increases.

Putting these processes together, my day would start accordingly:

I would set the steam-box up and fill it up with near boiling water, letting it warm up for about half and hour. Monitoring the temperature, via the thermometer, I would let it get up to as close to boiling as it would go. I would then load the wood in strips, separated by small chocks of oak, so the lignin doesn’t stain the wood. The wood would then be allowed to steam for about an hour. Fortunately, the steam vessel could allow for the steam time, and didn’t need to be refilled midway through.

At this point you are all too aware that the zero hour is nigh, and the steaming is imminent! You must have all clamps at the ready, in position and screwed ready to clamp on. I can’t tell you how many times I’ve forgotten this step, knowing that I’d have to reset a clamp to position it onto the jig and would waste precious seconds, and seconds is really all you have here. On the plus side, the bend is not the most extreme one; not like at NIDA, where Sarah’s chair required the entire props department manning a clamp each as the steamed beech was fired out of the box and into the jig pronto!

Once all the chocks are shaken loose, the timber goes straight into the opened jig and levelled as best as possible and then, one by one the clamps are tightened, and the timber is left for 24 hours to set.