Why good frames spend 5 days in a barrel of wood chips

Tumbling is why a good acetate frame feels glassy and warm instead of sharp and dull. After CNC cutting, frames go into rotating barrels of wood chips and polishing compound — coarse chips first to knock down tool marks, then progressively finer stages to build the shine. In our workshop that's 3 barrel stages over about 5 days. Skip it (or cut it to one day) and the frame looks fine in photos but feels wrong in the hand.

The three stages

Stage	Media	Duration	What it does
1 · Cutting down	Coarse bamboo/birch chips + abrasive	~2 days	Removes CNC tool marks, softens edges
2 · Smoothing	Finer chips + compound	~2 days	Evens the surface, starts the sheen
3 · Luster	Fine media + polishing wax	~1 day	Builds the deep, glassy finish

How to spot a frame that skipped it

1. Edges: run a fingernail inside the lens groove — sharpness means minimal tumbling.
2. Shine: heavy buffing-wheel gloss with flat spots = polish applied at the wheel only, not built in the barrel.
3. Corners: tumbled frames have softly broken corners everywhere, including spots a wheel can't reach.

Barrel time is the honest cost inside a frame's price — barrels take floor space and days, and there's no shortcut that survives the fingernail test. It's also why our sampling takes 10–15 days instead of 5: the timeline includes the full tumble, so your approval sample feels exactly like production.