We start with the heart of the brew house: the mash tuns.
“The six malt mills are of the two-high four-roller type, each having a capacity of 30 quarters per hour. Each of the six mash tuns, designed for a mash of 110 quarters, is a circular cast-iron unit 20 ft. in diameter and about 7 ft. deep, the lower portion of the tun being insulated with plastic magnesia 2.5 in. thick. The mash tun covers are of copper with the usual balance-weight lifting gear. The false bottom plates are of gunmetal with 22 s.w.g. slots, i.e. 0.028 in. wide. These plates are regularly cleaned about every four months with a hot caustic soda solution. The liquor space below the false bottom plates is 2.5 in. At present, the bottom of the mash tun is cleaned by lifting all false bottom plates which involves a considerable amount of labour, but the fitting of a pressure nozzle cleaning system is being considered, which will reduce the frequency of the laborious lifting and replacing of the false bottom plates from being a daily routine, to perhaps a weekly one, or longer. Each mash tun has its own independent geared drive unit driven by a 10 h.p. motor and provision is made for coupling up the drive units of adjacent mash tuns by means of an extension shaft should there be a prolonged failure on a driving motor during the mash. The sparge arms are driven through a unit gearbox.”
Journal of the Institute of Brewing Volume 55, Issue 5, 1949, pages 281 - 282.
That tells me so much. Time for some brew house maths. Remember that I worked out, based on the OG of Guinness at the time, that they could brew around 5.25 barrels per quarter. Giving around 605 barrels per brew per mash tun. Which tallies with the figures we’ve seen for output so far.
Remember each mash tun had its own malt mill. At only 30 quarters ground per hour, it means that it would take almost four hours to grind the malt for one brew. They’d have to have a mill per mash tun because they brewed in parallel. Given the length of time each brew took to get from mash tun to fermenter (20 hours), they had little choice.
Plastic magnesia is magnesium oxychloride cement. Evidently it’s hard, dense and strong. Which sounds like the sort of material you’d want for insulation.
Manual cleaning below the false bottom sounds like a right pain. Though probably no worse than emptying spent grain by hand. I’ve watched others do that. Looks like an excellent way of shedding excess pounds. Far too much like hard work for my taste.
It’s not totally clear what the drive unit was for. Was it to drive the sparge arm or did the mash tuns have internal rakes?
Next the coppers.