# The Part Hewn Shop Notes · https://hewn.build/shop-notes/the-part 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 Part." Hewn Shop Notes, hewn.build/shop-notes/the-part. Drafted 2026-05-02; AI-drafted, not yet checked. --- The session doesn't fail when the wood snaps. It fails ten minutes before you load the box, when you reach for a blank you should have rejected two days ago. Get the blank right and the bending is almost automatic. Get it wrong and it doesn't matter how good your box is or how accurate your form is. Everything in the last three posts — the physics, the box, the form — was preparation for this moment. This post is about the blank. **Grain first, species second** You know the species ranking by now: ash at the top, then cherry and hard maple, then quartersawn white oak. That ranking gets you to the right pile of lumber. It doesn't tell you which board in the pile to use. Two boards of ash can behave completely differently in the box. One bends clean. One splits at the apex and ends your session. The difference is almost always grain. Straight grain is the variable that matters most. Bending stretches the outside face and compresses the inside face. The bending strap handles the tension side. You handle the compression side by choosing a blank where the grain runs parallel to the long axis and doesn't deviate. Short grain, interlocked grain, grain that runs in and out of the face — all of these fail under compression. You cannot strap your way out of a bad blank. Check it three ways. End grain first: the rings should run close to perpendicular to the face. Rift-sawn is better for steam bending than flat-sawn. Face grain next: the lines should run straight down the length of the blank. Then sight along the length under raking light. If the grain lines weave, the board bends there. Reject: knots anywhere in the bending zone, interlocked or wild grain, end checks, reaction wood. Sapwood is fine. Color variation is fine. A beautiful board with a knot at the apex is firewood. **Moisture content** Counterintuitively, dryer shop stock — 8–12% MC — bends, but not as well as wood at 15–20%. The reason is the same as the plasticization physics: lignin needs both heat and moisture to soften properly. More moisture means a longer bending window and better compression tolerance. Most of us are working with kiln-dried stock at 6–10% MC. That works. Two adjustments: add 30–50% to standard steam time, and move faster when the blank comes out. The window is shorter. Don't soak a kiln-dried blank in water to compensate. You'll wet the surface but not the core, and uneven moisture means uneven bending. Steam penetrates more usefully than soaking — it delivers heat and moisture together at depth. Soaking delivers cold water at the surface and nothing else. If you're planning a bending project weeks out, store the stock somewhere more humid. Even moving it from a heated shop to an unheated space for a few weeks can raise the MC enough to matter. **Blank dimensions** Oversized means meaningfully oversized. After bending you will lose material at both ends to end checks. You'll lose thickness — 1/32″ to 3/32″ per face — to compression wrinkles and surface checking that get planed off. You'll lose length at the transition zones where the geometry isn't exact. Add 4–6 inches to finished length. Add 1/8″–3/16″ to finished thickness. Width doesn't change in bending; keep it close to finished dimension. Rip and plane the blank to final oversized dimensions before the session. Surface irregularities cause uneven steam penetration. Uneven steam penetration causes uneven bending. A planed blank responds consistently. **Mark the tension face now** The bending strap rides against the outside of the curve — the convex face, the tension face. Get this wrong and the blank fails in tension on the side the strap should have been protecting. It's the most common setup error in a first session, and it ends the session immediately. Mark it before the blank goes anywhere near the box. Pencil arrow, direction of travel, visible at a glance. You're moving fast at the moment of bending. The mark is not a reminder — it's insurance against moving fast in the wrong direction. **Five items, two minutes** Before every blank enters the box: 1. Grain confirmed — straight, no defects in the bending zone, rift-sawn preferred. 2. Dimensions confirmed — oversized in length and thickness, width correct. 3. Tension face marked — arrow visible, direction clear. 4. Form staged — clamps positioned, cauls ready. You cannot set this up after the blank comes out. 5. Timer ready. If any item fails, the blank doesn't go in. The checklist is where the decision is made. Once everything clears, there's nothing left to decide. Load the blank, start the timer, close the box. Don't hesitate at loading. The blank is ready. The form is staged. The steam is up. Hesitation costs you temperature and moisture — the two things you've been building for the last hour. Go.