Keeping it under the brine
Updated
Why the depth is specified
Brine excludes air. The organisms you want work without it and several of the ones that spoil a ferment need it, so the surface is the boundary between the process working and the process being colonized. A cucumber half out of the brine is not a slightly worse pickle; it is in a different environment from the rest of the batch, and it will seed the vessel it is sitting in.
One to two inches is enough that normal handling, evaporation over weeks, and the vegetables settling do not expose anything. It is a margin, not a measurement to hit exactly.
Holding it down
Cucumbers float. They float harder as fermentation produces gas, which means the problem gets worse over the first week rather than better, and a weight that was adequate on day one may not be on day four.
- A weight sized to the vessel mouth rather than a plate that tilts.
- Food-grade materials only. This is the page where the no-metal rule bites, because a weight sits in acid brine for weeks.
- Check it rather than trust it. The first week is when it moves.
The surface is a job, not an event
A ferment is not unattended for three weeks. Scum forms at the surface and the published problem tables name scum left in place as a cause of soft pickles, so removing it is part of the process rather than tidying. That is the tending page, and it is the reason a ferment has a labor cost a quick pickle does not.
At production scale this is the hidden constraint. Ten vessels is ten surfaces to check, and they do not wait for a convenient day. It is worth knowing before you decide how many ferments to run at once, because the limit is usually attention rather than floor space.