# The Box Hewn Shop Notes · https://hewn.build/shop-notes/the-box AI-drafted, not yet checked: Drafted by Chip, the writing system Hewn runs on Claude, from Hewn's craft corpus. Jonathan Salomons has not read this note yet, and no outside reader has checked it. Read it as a shop note: check a number before you cut to it. Cite as: "The Box." Hewn Shop Notes, hewn.build/shop-notes/the-box. Drafted 2026-05-02; AI-drafted, not yet checked. --- The steam box is not the hard part. People spend real time building elaborate boxes with latched lids and pressure gauges and silicone gaskets. The box is a sealed wooden chamber with a hole at the bottom and a hole at the top. It doesn't bend wood. Your session discipline does. Here's how to build one and run it correctly. --- ## Building the Box Use cedar or pine. Exterior-grade plywood works too. What doesn't work: MDF, interior-grade ply, any panel product that delamines when wet steam hits it repeatedly. You'll ruin an MDF box in three or four sessions. 3/4" walls are adequate. Thicker is heavier for almost no thermal gain. Size the interior for your longest anticipated part plus a few inches at each end. Cross-section slightly larger than the widest part. Steam needs to move around the workpiece. A box that fits the part like a coffin is an oven, not a steam box. Drill a 1/2" hole at the lowest end. Condensate forms on the walls and the wood and runs downhill. If it pools, the bottom of your part sits in water, not steam. Put a container under the hole and let it drip. A small gap or hole at the high end lets steam exit and prevents pressure buildup. You are not trying to pressurize anything. Free-venting steam at atmospheric pressure is what you want. Run 3/4" dowels through the box to hold the part off the floor. Steam contact on all four faces. A part resting on the box floor gets cooked on the bottom and steamed on the other three. That's not even. The lid needs to fit well enough to stay closed. Friction fit or simple wooden stops is fine. A small gap is acceptable. A lid that falls open mid-session is not. Hinge it to open away from you. The steam that escapes when you crack it is hot enough to matter. --- ## The Steam Source An electric steam generator is the cleanest option for a furniture shop. Plug it in, fill the reservoir, wait for the ready indicator. No open flame, manageable indoors with ventilation. A 1500-watt unit handles most furniture-scale parts without trouble. A camp stove with a stainless pot and a silicone hose to the box also works, and it costs almost nothing. The limitation is that you can't see the water level easily. A pot that runs dry mid-session doesn't just stop working — it actively damages the part for the tail end of the timer. The dry heat desiccates the wood instead of softening it. Use a larger pot than you think you need and check the water level before you start the clock. The wet steam requirement is not negotiable. The lignin softening mechanism needs both heat and moisture simultaneously. Know your reservoir volume. Calculate your consumption. Plan a 20% buffer for generator efficiency variation. --- ## Session Discipline Once the part leaves the box, there are no safe stopping points. Every element of the session gets staged and rehearsed before the steam comes on. **Rehearse it first.** Test the form. Confirm clamp positions, which face of the part seats against which face of the form, the exact motion required. Stage the bending strap — fitted, in position. Pre-open all clamps on the bench near the form. Then walk through the full bending motion without the part. Multiple times. You're building muscle memory of what you'll do in 90 seconds, not thinking it through in the moment. **Then run steam.** Preheat the empty box for 10–15 minutes before loading the part. Cold walls absorb heat from the first portion of the session. You want the box interior at temperature when the wood enters, not warming up while the clock ticks. **Session sequence:** 1. Fill the generator and start preheating the box. 2. Load the part when the box is fully preheated. Note the time. Set a timer. 3. When the timer ends: open the box, retrieve the part with gloves, strap on immediately, part into the form. The 90-second clock starts when the part leaves the box, not when you find the gloves. 4. Clamp progressively from the center of the bend outward. You're seating the bend, not crushing the fiber. 5. Leave the part in the form until fully cooled and dry — overnight minimum, 24–48 hours preferred. Release it early and springback will exceed your calculations. --- ## Cold Shop (BC Interior) Cold ambient temperatures pull heat from the box faster than in a temperate shop. Extend the preheat to 15–20 minutes instead of 10. Warm the form and the work area before bending. A few minutes with a heat gun on the form surface is enough. Cold bench, cold form, cold air — the part loses temperature faster on contact, and the window compresses. Expect 60–70 seconds instead of 90 on a cold morning. Speed matters more than it usually does. Run steam bending sessions in the warm part of the day, shop at working temperature. Same logic as glue-ups and finishing: you're managing conditions, not just the part. In Penticton, that's midday, not 7 a.m. in January. One upside to dry winter air: the steamed part releases moisture faster during set. Drying time in the form may be shorter than humid coastal conditions. Track this by season. --- ## The Actual Point A simple site-built box with an electric generator and the session workflow above will produce consistent bends. An expensive commercial setup run without pre-heat discipline and an unstaged form will produce inconsistent ones. The box is infrastructure. The discipline is the technique.