Does hook material actually change my gauge?

Every loop you pull up has to slide over the hook's shaft. A smooth aluminium hook lets the yarn slide with very little resistance, so the loop ends up slightly larger. A bamboo hook grips, the loop stops sooner, and the stitch is 3-5% smaller for the same hand motion.

The effect compounds on tall stitches: a dc has more shaft contact than an sc, so the aluminium-versus-bamboo gap is wider on a dc fabric than on a single crochet fabric.

Resin and plastic hooks sit closest to aluminium in friction and are the lightest, which matters over a long session. Metal hooks with an ergonomic grip change the angle of your wrist more than the friction, and that angle change alone can move gauge by 2%.

Coated hooks — the ones with a coloured finish — sit between aluminium and bamboo. If you have hand pain, choose by handle shape first and material second, then re-swatch; the gauge difference is smaller than the difference a painful grip makes to your tension.

Switch at a round boundary, never mid-round, so any gauge change is a clean step rather than a wobble in the middle of a round. Then compensate: going from bamboo to aluminium is like going up a quarter hook size, so work one plain round before continuing the shaping.

If the change is forced and the piece is a stuffed shape, work the rest of the piece with the new hook and accept the 3% difference. It disappears into the stuffing, and unstuffing a half-finished piece is far worse than a slightly uneven one.