I've made up a batch and put the fermenter in the fridge to cool down. Its at 20 degrees C currently and 20L. How long would you think it would take to cool down to pitching temp and what pitching temp should I be aiming for?
Ideally, you're aiming for ~10°C or a little less. It should only take a couple hours, but keep your fridge on the coolest setting until it gets there. If you need a way to tell the temperature without risking contamination, try this bubble-wrap method: