Humidity and chocolate work
The overlooked variable. It does not affect crystallisation directly, and it ruins the results anyway.
If you read nothing else
Humidity does not affect crystallisation and does ruin the results, by condensing on any surface cooler than the air. Keep the room below 50% and never work with a cold mould.
What it does and does not do
Humidity does not change how cocoa butter crystallises. Tempering is a temperature process and the curve is unaffected by the air's moisture content.
What humidity does is put water where chocolate cannot tolerate it. Above roughly 50% relative humidity, moisture condenses on any surface cooler than the air — a marble slab, a mould taken from a cool cupboard, a bowl — and that water seizes the chocolate or marks its surface.
Where it shows up
Sugar bloom on setting pieces, as surface moisture dissolves sugar which recrystallises. Dull, mottled finishes on moulded work. Sticky, tacky surfaces on decorations that should be dry.
And seizing that appears to come from nowhere, because the water arrived from the air rather than from anything anyone added.
What to do about it
Work in the driest room available and avoid running a kettle or a hob in the same space. Bring moulds and slabs to room temperature before use rather than taking them straight from a cool place, so nothing is cold enough to condense on.
Professional chocolate rooms hold humidity below 50% deliberately, and it is one of the two environmental controls a chocolate kitchen actually needs — the other being temperature.
Covered in this guide
- Making hollow figures and Easter eggsMoulded work, where condensation on a cold mould shows most.
- Temperature controlThe other environmental control, and the numbers for it.
- Chocolate in a warm kitchenThe temperature half of the same problem.
- Preventing bloomWhat condensation produces, and how to avoid it.
Sources
- ChocolateHQ editorial synthesis — ChocolateHQ(citation identity confirmed; passage not re-read)
- The Science of Chocolate — Royal Society of Chemistry(citation identity confirmed; passage not re-read)