Here's what I've got so far on that staple of 18th century London brewers, brown malt.
Brown malt was the cheapest. Unlike modern versions, that produced in the 18th century had sufficient enough diastase to be employed as a base malt. Early Porter and Stout were brewed from 100% brown malt.
As brown malt was dried more quickly and with a higher temperature, there wasn't so much need for accurate temperature control as with pale or amber malt. The finished malt was quite hard and sometimes even partially burnt.
"The brown Malt is the soonest and highest dryed of any, even till it is so hard, that it's difficult to bite some of its Corns asunder, and is often so crusted or burnt, that the farinous part loses a great deal of its essential Salts and vital Property" "London and Country Brewer", 1736.
The brown malt used by London brewers was kilned using straw as a fuel. Straw had two advantages over wood. It was less expensive and didn't impart a smoked flavour. London brewers weren't keen on smokiness in their malt liquors and, when forced to use wood-dried malt, usually matured the finished product until all traces of smoke had disappeared.
Various writers have claimed that early Porter was smoky from the use of wood-dried brown malt. There's no evidence from the period to support this theory, but plenty to contradict it.
It is without doubt true that there was brown malt dried with wood and it did have a smoky taste. Yet the way it was perceived is not quite as some may have you believe. Smokiness in beer and ale wasn't appreciated in the same way as the peat character of malt whisky is today. The reaction of your average modern German drinker after tasting Bamberg smoked beer is closer to the mark - a mixture of disgust (that beer can taste so horrible) and amazement (that anyone can drink such muck for pleasure).
It's no different with West Country smoked malts. Writers of the period describe the distinctive taste derived from wood-smoked malts, and the almost universal revulsion it engendered. The smoked beers and ales of the West Country were famous for being undrinkable - locals and the
desperate excepted. This is from "Directions for Brewing Malt Liquors" (1700):
"In most parts of the West, their malt is so stenched with the Smoak of the Wood, with which 'tis dryed, that no Stranger can endure it, though the inhabitants, who are familiarized to it, can swallow it as the Hollanders do their thick Black Beer Brewed with Buck Wheat."So, a bit of an acquired taste, then. Here's an even earlier reference to such malt by William Harrison, in his "Description of England", 1577:
"In some places it [malt] is dried at leisure with wood alone, or straw alone, in other with wood and straw together, but, of all, the straw-dried is the most excellent. For the wood-dried malt, when it is brewed, beside that the drink is higher of colour, it doth hurt and annoy the head of him that is not used thereto, because of the smoke. Such also as use both indifferently do bark, cleave, and dry their wood in an oven, thereby to remove all moisture that should procure the fume..."Not exactly an unequivocal endorsement. Here's what "London and Country Brewer" (1736) has to say:
"Brown Malts are dryed with Straw, Wood and Fern, etc. The straw-dryed is the best, but the wood sort has a most unnatural Taste, that few can bear with, but the necessitous, and those that are accustomed to its strong smoaky tang; yet it is much used in some of the Western Parts of England, and many thousand Quarters of this malt has been formerly used in London for brewing the Butt-keeping-beers with, and that because it sold for two shillings per Quarter cheaper than Straw-dryed Malt, nor was this Quality of the Wood-dryed Malt much regarded by some of its Brewers, for that its ill Taste is lost in nine or twelve Months, by the Age of the Beer, and the strength of the great Quantity of Hops that were used in its preservation."Wood-dried malt had a horrible taste, but some London brewers did once use it because it was cheap and after long aging in a heavily-hopped beer you didn't notice the vile smokiness any more.
I will admit that all the fuels used in the drying of malt, apart from coke, exposed the grain to some degree of smoke. However, the straw-dried brown malt preferred in London was the least affected. That was the very reason it was valued above the wood-dried variety. In "Town and Country Brewery Book" (approx. 1830, p.47), there is a chapter about what can go wrong during malting. Smoking malt was seen as a serious mistake:
"The third error consists in the drying of malt. They are apt to be tainted by the smoke, through the carelessness, covetousness, or unskilfulness of the maker. Every care ought to be taken to guard against this accident as one of the most prejudicial that can befall malt drinks."As brewers and malsters were doing their best to avoid it, I find it unlikely that much smokiness was perceptible in finished porter. Remember that it was being aged (in the case of the earliest porters, four to five months). If nine to twelve months was enough to rid beer of the stench of West Country malt, then a couple of months would have been plenty for the far milder straw-dried malt.