Now I always thought that the point of a cellar is that the temperature inside it was pretty constant, no matter what the weather outside. Evidently, this isn't the case. As we learned earlier, 55º F was the perfect temperatue for cask beer. There's a little moe explanation as to why this was the case.
"A thermometer should be kept in every section of the cellar, and if one side is likely to get warmer than another, then more than one.Of course, nowadays there are less messy ways of keeping a cellar cool than sprinkling cold water all over the cellar.
In the beer cellar it is useless to hang it anywhere but on the level of the barrels.
Beer which is kept at a higher temperature than 60°, or a little over, goes "off" and comes up warm.
Beer kept at a lower temperature than 50° goes "sick," and is very unpleasant.
Therefore, if you are ever making any alterations to your house that affect hot-water or heating services, have a care that neither affects your cellars, and look carefully at the design with this end in view.
The cellar should be well ventilated and without draughts.
During cold weather, a stove or gas-burner should be used, and, in addition, hop sacking or bags should be used to cover the casks.
During hot weather, sprinkle the floor with cold water, and cover the casks with bags, soaked continually in cold water.
All the instructions regarding the treatment of beer are most important, as upon them depends the condition of what may be the staple commodity you sell.
Your customers will be severely critical of your beer, and are fine judges.
They judge not only by flavour, but by condition, brilliancy, and temperature."
"The Art and Practice of Innkeeping" by Alexander Francis Part, published by Heinemann London, 1922, page 201.
The 55º F temperature is clearly connected to the need for the beer to ferment in the cask and condition the beer. Presumably, below 50º F was too cool for a proper secondary fermentation to take plce. While above 60º F there is too high a risk of the beer becoming infected. As well as the rather obvious problem of the beer being too warm in the glass.
Although the condition of the beer was central to a pub's success, I know from the comments in the Whitbread Gravity Book that there was a lot of poor-quality draught beer around in London. Clearly plenty of pubs managed to get away with dodgy draught. Is that a sign that customers weren't always quite as discerning as Part makes out?