# 028 — Grain Warp

## Problem Situation

Woodworkers designing furniture with solid wood must account for seasonal wood movement — expansion and contraction driven by humidity changes. Wood moves anisotropically: tangential movement (across the growth rings) is typically 1.5x to 3x greater than radial movement (along the rings). This invisible directional differential is what causes flat-sawn boards to cup, cross-grain joints to self-destruct, and tabletop panels to crack.

The problem is not lack of data. Shrinkage coefficients exist in the Wood Handbook. Online calculators return numbers ("your board will move 3/16 inch"). But numbers do not convey the spatial, directional nature of the movement. A woodworker reading "T/R ratio 2.99" cannot feel what that means for a board, a joint, or a panel.

## What Was Built

A wood movement deformation instrument. Two canvas-rendered visualizations side by side:

1. **Log cross-section** showing growth rings that deform into ellipses as moisture content changes — tangential expansion stretches the rings wider while radial expansion stretches them taller. Directional vector arrows show the magnitude and direction of movement at four compass points.

2. **Board cut comparison** showing the same species as flat-sawn and quarter-sawn cross-sections, with exaggerated cupping deformation. The flat-sawn board visibly cups because its tangential face (wider movement) is across the width, while the quarter-sawn board stays nearly flat because its radial face (narrower movement) is across the width.

Six wood species with real coefficients from the Wood Handbook. Moisture content slider from 3% (oven dry) to 18% (green wood). Four environment presets. Season Cycle animation that oscillates moisture to show the wood breathing through a year. Species comparison table showing flat-sawn vs quarter-sawn movement and the percentage saved by quarter-sawing.

## Why This Form

The problem is directional and spatial — wood moves differently in different directions relative to the grain. The only honest representation is spatial: a cross-section where the directionality is visible as shape change. A number table hides exactly the thing that matters most: the direction and differential.

The flat-sawn vs quarter-sawn comparison is the instrument's strongest move. Placing them side by side at the same moisture change makes the invisible advantage of quarter-sawing viscerally legible — not as a fact to memorize, but as a shape you can see.

## What Is Interesting

The T/R ratio is the hidden number governing most wood movement disasters, and it varies dramatically by species. Eastern White Pine has a 2.99 ratio — meaning its tangential movement is nearly 3x its radial movement. Black Walnut is only 1.44. This single number predicts how aggressively a board will cup, but it is buried in reference tables and never shown spatially.

The Season Cycle animation is surprisingly revealing. Watching a cross-section breathe through a humidity cycle makes the living nature of wood movement feel real in a way that static numbers never can.

## Iterations

- v1.0: Core instrument with log cross-section, board comparison, species table, readings, and contextual insight text.
- v1.1: Larger, thicker board cross-sections with more visible ring lines. Added Season Cycle animation button. Increased cupping exaggeration for clearer visual differentiation.

## Next Step

Add a cross-grain joint visualizer: show two boards meeting at 90 degrees and watch the joint fight itself as moisture changes. This would make the most dangerous woodworking mistake (gluing cross-grain) visually obvious.

## Art Direction Note

Dark theme, editorial minimalism. Geist + JetBrains Mono. Monochrome-first palette with restrained rust-red for expansion and muted blue for shrinkage. Wood species rendered in their approximate natural colors. Follows the Night Lab default direction.

## Promotion Candidate Read

Maybe. The form-to-problem fit is solid — directional movement shown directionally. The species comparison table and flat-sawn vs quarter-sawn contrast are genuinely revealing. But the instrument stays within the parameter-space instrument family that recent builds have explored heavily (017, 021, 025). The cross-section deformation is a visual instrument, not a new artifact class. Stronger than a calculator, but not a category breakthrough.
