Carr's description of brown malt and its manufacture is intriguing.
I find this phrase about brown malt very revealing "its sole object in porter is to communicate flavour and colour". It got me thinking about the role of brown malt in Porter and how it changed at the end of the 18th century.
"Strictly speaking, there are only three varieties of malt, viz. brown, amber, and pale malt. The first two are peculiar to porter, and have special reference to its flavour and colour; the third is the general basis as well of all porter as of every other species of malt liquor; and it is the only one which merits any consideration in the general question of malting. Brown malt receives all its peculiar qualities in the kiln, by an operation called blowing: it is spread there very thin, and a very quick and active heat is passed through it from flaming faggots: the sudden application of the heat converts the moisture in the grain into vapour, which blows up the husk, and the heat catching it in its distended state hardens and prevents it from collapsing; hence the grains of such malt are large and hollow, and increase the measure from one to two bushels in a quarter. The saccharine of this malt is nearly all destroyed by the operation of the fire, and its sole object in porter is to communicate flavour and colour; but as these qualities are probably to be obtained from other materials than malt, some porter-brewers are not using it at all, and the making of it is very rapidly declining. Amber malt is a species between brown and pale, and is also made on the kiln by giving it less fire than the former, and more than the latter; it is still generally used in porter along with pale malt, but the quantity made is inconsiderable."
On Malting, John Carr, Esq, 1807
[From Papers presented in the House of Commons relating to the
Sprinkling of Malt on the Floor. Ordered to be printed l0th of August, 1807]
Presented to the Committee of Enquiry into Malting
Taken from The Philosophical Magazine, Vol xxxi, 1808
Before the hydrometer revealed that pale malt was far more economical, Porter had been brewed from 100% brown malt. That in itself tells us that the brown malt of that time was very different stuff to that of the 19th century onwards. Later brown malt had no diastatic power. It didn't need to, because there were sufficient enzymes in the pale malt base. The purpose of brown malt in a brew had changed. It was just being used for flavour and colour, as Carr wrote.
These are Porter and Stout grists from around the time Carr was writing:
The 19th century descriptions of brown malt manufacture in Hertfordshire differ from those of the previous century. In the 18th century Hertfordshire maltsters used straw to fuel their kilns. I can find no reference to the use of wood to suddenly increase the temperature at the end of the process.
The percentage of brown malt in Porter had fallen below 50% by the early 1800's. Could blown malt have been a reaction to this? Something that had more flavour and more colour than the old brown malt to compensate for the reduction in the amount used in a brew. Was blown malt a precursor of black malt?