As the mash heats and thins slowly, it will pass through all the relevant temperature bands for activating all the grain's enzymes
This is very interesting; there must be a lot of traditional mashing styles that operate on a similar principle, and brew days really could be just that - going in duration for all day, or several days. It's occurred to me that for a person with no specific knowledge of enzymes, relevant temperatures, etc - ie, a person in a traditional beer making culture - the simplest, most obvious way of mashing is simply to take water from a nearby stream, add grain, and slowly and patiently heat it over hours, or even days.
Here's one traditional brew description - the mash went on for several days! I'm quoting from Randy Mosher's Radical Brewing, which is quoting from John P Arnold's The Origin and History of Beer and Brewing, who is himself quoting from G Radde's Die Chewsuren and ihr Land. Three quotes in one, not bad.
Where clumps of ancient trees are massed in close array - oak, maple, and ash - we have before us the sacred groves of the Chewsures, preserved by them with veneration; and within them may be found their pagan sacrificial altars, as well as their beer breweries... At the lower edge of the small wood, close to the field of barley, which together with the adjoining meadows, is held the property of Saint George, there stands a roughly constructed hovel, the place for sacrificing. This poor structure is low, dark inside, carelessly put together from flat slabs of slate, and for the moment it was not guarded by anybody. All the implements kept inside, especially the huge beer-tubs, tankards, drinking cups, and the manifold apparatus for brewing, are also looked upon as the property of the guardian angel in question. In the other sacred grove to the east of Blo, they happened to be brewing beer against the approaching holidays; that was why I went thither to be an eye witness to the process.
From the brewer of Saint Michael there escaped a continuous cloud of smoke. Malting was going on there, and the acrid smoke, occasioned by the damp brushwood which had to serve as fuel, together with the escaping steam wrapped the brewhouse completely in a dusky mantle. The brew-house, too, was built in the rudest way, low and insufficiently lighted. There, by a mighty chain, hung the huge copper brew-kettle. Its form is peculiar, and everywhere the same. In its form it most closely resembles a giant top, being from 1 1/2 to 2 arsheen high (3 1/2 to 4 1/2 feet) and at its greatest width about 1/14/ arsheen (3 feet) wide. It begins to belly out at a point above the middle. Artisans of Telaw fashion caldrons like these, their value being somewhere between 100 and 200 roubles. Laterally, this cauldron is held up by carelessly joined stone rubble, while sooty flame licked at it in front and behind. The mash was bubbling in it at a uniform rate, and was stirred now and then. Water was conveyed from the nearby brook through a small pipe that was laid against the outer edge of the cauldron. The crushed barley that is used for the mash is coarse, and is boiled steadily for several days at an even temperature. Then the brew is run into woolen bags, and the latter are fastened above the rim of a vat, using wooden hoops for the fastening, so that the liquid slowly runs into the vat below. The fresh brew thus made, is turbid, rather insipid, and sweetish in flavour. It is poured into tubs 3 or 4 feet high, and 2 to 2 1/2 feet wide, made of one piece (from sections of tree trunks hollowed out), basswood being mostly used for this purpose. Then the required amount of Kakhetian wild hops is added, and the liquor, well covered up, is allowed to stand for 5 or 6 days.
Everything about these consecrated brewers is grimy with smoke and soot, as is also the case with the dwellings and watchtowers of the Chewsurians, and all the implements to be found upon the sacrificial altars and the breweries is considered the personal property of the guardian angel, and is correspondingly venerated."
Radde further relates that women were excluded from the groves, shrines, and breweries. Female participants in festivals remained behind boundaries, with beer and food served to them there.
The brew incorporated with wild hops and malted barley that is dried - and develops colour - over the course of several days, on racks positioned in the eaves of the houses, above the heat of the hearth. Fermentation was done in capacious earthenware pots buried in the ground, large enough for a man to descend into using a ladder.
So now you know how to make Chewsurian ale, "described as brown in colour, reminiscent of dark Bavarian beer, although "imperfectly clean"". Says Mosher. Or Arnold. Or Radde. (Hard to tell.)
