Capping and shrink bands

Capping is the last operation that can ruin a good batch, and it is the one done fastest and with least attention.

Capping by hand

Seat the reducer, place the cap square, and turn until it stops. The failure mode is cross-threading, which happens when a cap goes on at an angle under speed and produces a bottle that appears closed and leaks.

Check a sample from each run by inverting and holding. A bottle that weeps at the thread now will arrive wrapped in its own contents.

Torque matters more than force

Too loose and the seal fails. Too tight and the liner distorts, which also fails, and the customer cannot open it. Hand tightness varies enormously across a session, usually getting tighter as you speed up.

A torque check on a sample from each run is the cheap control. Consistency here is worth more than any particular target.

Shrink bands

Slide the band over the closure, overlapping cap and neck, then heat evenly. A heat gun works; the trick is even coverage and keeping moving, because a band held too long in one place burns and one held too briefly stays loose.

Size to the closure and neck, not to the bottle body. Bands are specified by lay flat width and the fit is unforgiving in both directions.

Do it on cool bottles. Shrinking a band onto a warm bottle gives a band that is loose once everything reaches room temperature.

Where the run slows down

Capping and banding are the operations that set the pace of a hand-bottling day, not filling. Producers routinely buy a better filling setup and stay bottlenecked at the cap.

Time the steps before buying anything. The bottleneck is usually not where it feels like it is, and it is almost never the machine that is most fun to shop for.

References