Roberts thought some brewers caused themselves problems by mashing at too high a temperature. Over-attenuated IPA's were the result. 168º to 170º F he recommended as a striking heat when the ambient temperature was 40º to 45º F. If the air temperature was 35º to 40º F, 170º to 172º F was his suggested striking heat. When the wort was tapped at the end of mashing, its temperature should be 145º to 150º F .
Mashing – the process of actively mixing the grains with water in the tun – needed to be as quick as possible, no more than 20 to 25 minutes if using internal mechanical rakes. At the start of mashing the temperature was checked at various points in the mash. If it was much below 145º F, hot water was added to raise it to 150º F. When mashing finished the wort was left to stand for between 100 and 120 minutes .
Roberts recommended kicking off sparging a few minutes before drawing off the first wort, using water between 185º and 190º F. The taps were closed as soon as the first wort had been run off. While sparge water continued to be added until the grain bed was covered again. Because, Roberts commented: "it being highly detrimental to let the surface of the goods to be dry” .
His suggestions for hop additions are very much based around gyle brewing, where each gyle was hopped and boiled separately. For a beer hopped at 22 lbs per quarter of malt (5 to 7 lbs per barrel, depending on the OG), 6 lbs were added to the first wort at the start of a 70 minute boil, a further 8 lbs were added 20 minutes later. The second wort received a single hop addition of 8lbs at the start of a two hour boil.
Rapid cooling of the wort after boiling was important:
"Reducing the temperature of worts in the coolers is now generally accomplished by artificial means, and with great rapidity, it being important that they should be reduced to the pitching temperature, with as little delay as possible."
"Scottish Ale Brewer", WH Roberts, Edinburgh, 1847, pages 165-166.
By artificial, he means that the wort wasn’t just left in a shallow cooler until it reached a suitable temperature for pitching yeast. But that it was also cooled by a simple heat exchanger. This consisted of a washboard of copper pipes filled with chilled brine over which the wort was run. This combined method of cooling was standard in British breweries until after WW II.
The pitching temperature Roberts recommended was 58º and 60º F, depending on the air temperature. He expected a rapid and vigorous fermentation with the temperature rising to around 70º F. After just 24 to 30 hours the beer passed on to the next phase: cleansing.
In this early phase of Pale Ale production cleansing still took place in puncheons, large casks holding several barrels set up vertically on stillions. Wort was ejected from the top of these vessels into a trough, from which the puncheons were refilled every two or three hours . This system of cleansing was common in the big London breweries, but in Burton – and later in Scotland, too - was replaced by the more sophisticated and less labour intensive unions.
The method of dry hopping Roberts proposes is a bit odd. The hops were mixed with a little boiling strong Ale wort, which, after cooling, was added to the casks of IPA.
Some brewers liked to deliberately rack their beer into trade casks with dregs, arguing that it helped prevent the beer spoiling during the long trip to India. Roberts reckoned it was better to rack IPA clear.
The above is an excerpt from my excellent book on Scottish brewing:
Which is also available in Kindle form: