My main source today is H. Stopes, author of the classic "Malt and Malting", published in 1885.
"The Manufacture Of Black, Amber, Crystal, And Other Special Malts.Hitherto we have been considering one class of malt only, viz. that technically known as pale malt. Several other varieties exist. Under this heading we shall consider those only which depend upon the conditions already explained, but with a variation of the final process of drying, such variation being chiefly a comparatively slight difference of temperature.What interests me about this passage is Stopes' dismissal of adding wood to increase the temperature of the kiln as an absurd and expensive practice that was disappearing. Though, it seems as if the practice survived into the lat 20th century. This is what Guy Horlock of French & Jupps has to say about making brown malt:
Amber, porter, blown, or imperial malt can be made in any ordinary malting, the
differences to which they owe their names being almost entirely effected upon
the kiln. The scope they afford to the engineer for employment or improvement is
infinitesimal. They deserve mention only for the impressive fact, that the difference in temperature which will convert pale malt into amber or imperial is actually less than is to be found in the vast majority of kilns, between the temperature of that pale malt lying upon the surface of the tiles or wire, and of the upper surface exposed to the air. There is probably no kiln in Great Britain having only a single floor in which this difference is less than 50°. Pale malt next the tiles will be at 200° Fahr., and upon the surface 150° or less; and malt heated to 240° would make amber or imperial malt.
Blown or porter malt has the further difference that considerable heat is applied with suddenness before it has become dried. It is well known that any given temperature over 100° Fahr. will give much more colour to malt if still moist than a much greater heat if dry. Blown malt is exposed to the flare of fast-burning oak faggots or billet wood, and gains much colour and increase of size in consequence. Its use is an absurdity that is dying out, for the colour and flavour so gained are found to be very costly.
Crystal malt is green malt not fully grown, taken straight from the floor, and placed in a woven wire cylinder over a fire, and rotated. The curious sweetness of crystal malt to the palate may be readily accounted for by the mode of its drying. Sufficient
moisture is present at considerable temperature to enable the diastase to convert a portion of the starch into sugar.
Black or patent malt is pale or other malt dried in the ordinary way, and then placed in a cylinder over a fire, and rotated. The starch and saccharine constituents are speedily caramelised, and a splendid deep colour is obtained, which is communicated to porter and stout. The chief difference in the appliances used in the manufacture
of these (crystal and black) malts is the construction of the furnaces and cylinders. They have to be made in such a manner that free inspection of the malt can take place during roasting. They must also admit of ready lateral movement to facilitate filling and emptying; and appliances for proper cooling are of importance."
"The Engineering of Malting" by H. Stopes, 1885 an article in "Transactions" journal of the Society of Engineers.
"We produced Brown Malt until 1980, but due to the dangerous nature of theSo it looks like the archaic practice of finishing roasted malts with faggots of wood didn't die out as Stopes expected. Anyone have any idea how they make brown malt nowadays?
manufacture, nobody would insure us after that date. I have been working for F&J since 1949 and I was involved quite heavily in the production of Brown Malt."
"All my period with the production, we have never used anything other than Hornbeam, both poles and faggots and I know that Taylors at Sawbridgeworth (later to become part of ABM) did the same. However I know that Swonnels at Yarmouth did use offcuts of Oak, simply because they has a woodyard (Jewsons) next door, but I have never heard of anything else in the production and never coal."
Extract from a letter written by Guy Horlock, curator, French & Jupps Museum, Stanstead Abbotts, Hertfordshire.
French (presumably short for French & Jupp) and Taylor are names that frequently crop up in the brewing logs of Whitbread and other London breweries. Usually it was either brown or black malt that they supplied.