When is a solid spile inserted into a cask?

A solid spile is inserted into a cask once fermentation has slowed to the desired level. This timing is crucial because, during the active fermentation process, the yeast generates carbon dioxide, which can lead to excess pressure in the cask. Inserting a solid spile too early could result in the cask bursting or overflowing. By waiting until fermentation has slowed, the brewer can allow for the naturally occurring carbonation to stabilize while still controlling the release of gas. This practice ensures that the beer develops its intended flavors and carbonation without the risk of over-pressurization. Inserting the spile later also allows the brewer to monitor fermentation progress and ensure that the beer is at the right stage for maturation and conditioning.