New Source To Understand 1700s Porter
As far as I know, no academic or other histories of porter have canvassed a 1760 book that describes in some detail the kilning of brown malt. It was published that year, in London, by an anonymous writer. The impressive title (yet still abbreviated) is The Compleat Dealer’s Assistant: Or, The Maltster’s and Mealman’s Useful Pocket Companion. The author claimed a 50-year history in the malting trade in England.
Certainly his book shows extensive experience and appears technically and historically credible.
Other 1700s accounts exist of brown malt, by William Ellis, also Thomas Hale, but not in this detail.
In his description of brown malt, which you can read here under “Of drying Brown Malt”, the author states of the “popped” form, which gets most of his attention, that it was one form of brown malt. Two other types are described in more summary form; these received progressively longer drying, at an overall lower heat. One can infer they retained more fermentable extract, as he states brewers prefer brown malt that is closest to amber because, buying at the brown price, they would “run away with the profit”.
A partial quotation:
Some Brewers chuse this very high blown, others in a middling way, but now (for the sake of interest) they will have it dried (if possible) as close as fine amber. I myself have blown as high as any person for chapmen in London (for making porter) in the following manner, which has given great satisfaction. The kilns are to be laid on quite thin, and when the malt has had two stirs, in about three quarters of an hour, make a large fire with good billet, well dried, slit small, and laid upon a strong iron bar across the oast hole. Let one man be employed to make up the fire, whilst two others constantly attend the kiln, to stir and keep it from burning, and relieve each other; and when your kiln has popp’d about half an hour, let the fire grow smaller and smaller till you throw off.
I read this that during the first 45 minutes when the malt is laid on the kiln, two stirrings are done, with no fire underneath. So that when the strong fire starts, the popping or swelling of the malt corns occurs almost right away. Even if that is not right, clearly the popping starts much earlier than was typical of 1800s production of brown malt.
The popping took a half-hour, and then the fire was banked down for approximately two hours more of kilning. After this the malt was taken out and would have been left to cool.
Even if popped brown malt was not the only malt for porter, it was clearly very popular, as he states he sold a lot of it to chapmen (dealers or vendors) for use to make porter.
Well-dried hardwood was the fuel, which produced relatively little smoke. It is obvious some of this smoke would still get in the malt, but as other 1700s accounts make clear, porter was often long-aged then, which would reduce the smoke taste.
This description of brown malt production is basically similar to a number of 1800s accounts, e.g., by William Ford in the 1850s, except for the difference of timing when the popping was done.
See also here, a detailed discussion mid-century in Britannica. The wetting, and blowing, of “brown malt” mentioned are after a prolonged drying on the kiln. The older blown malt is mentioned just after, but numerous accounts later refer to this as old-fashioned, almost out of use. See e.g., maltster Henry Stopes here for a typical account, late 1800s, of contemporary preparation of blown malt where the blowing and blistering take place after a lengthy, thorough drying.
Almost all the writers, at any period, seem agreed the earlier way of blowing malt was less productive, meaning in fermentable extract, but the question is whether it conferred a unique stamp on the original porter; I believe it did.
Hence the difference is important, in our view. When newly placed on the kiln, the malt would be at its moistest. It was either moist from the maltings or in some cases wetted before being placed on the kiln. Various 1800s sources suggest as well that the blowing or popping occurred at between 175-210 F, with the malt starting at about 90F, which is a mashable termperature. I infer the moist malt kernel would have been been caramelized, much as modern caramel malt is, with a quick initial heat, to produce a viscous dark sugar.
Modern caramel malt – which is sometimes made on a kiln, not a roaster – is not diastatic: that is, it has no enzyme content to convert starches to fermentable sugar. But it doesn’t need to be, as caramel malt doesn’t need to be mashed, or not for very long. Brown malt popped in the initial kilning stage, or blown or snapped in other usage, was probably a rough form of caramel malt. This would explain the many references in porter literature to caramel, bitter caramel, or burned caramel giving porter its unique taste. The sugar did that but also provided surely some fermentable material for conversion to alcohol.
In contrast, if you do the super-heating at the end of the kilning as occurred from about 1810 onwards, the barleycorns will be much drier. While the popping may still occur, I doubt you would get any starch conversion. This explains why numerous commentators in the 1800s stated brown malt wasn’t fermentable. You would still get colour contribution and some flavour. But by the 1800s brewers didn’t need fermentability from brown malt as it was mixed with a much larger amount of pale malt that supplied most of the fermentable material. Black malt, newly available from 1817, would have supplied the bitter grain or burned taste, as well.
In the 1700s, porter was still made from all-brown malt. Brown malt was always less efficient in extract than pale and amber malt since its drying at high temperature degraded part of the starch. Under these circumstances, it would make sense to blow or pop the malt when it had the highest moisture, to get some fermentable sugar which contributed also a unique flavour to the beer.
To those who might object that a strong initial fire would ruin the enzyme potential, two things may be noted. Good porter malt would not have needed much enzyme if it didn’t need much mashing. Second, some modern Dunkel malt (German brown lager malt) finishes at 212 F and remains enzymatic to convert all its starches to sugar Same thing with Rauch or smoked malt for Bamberg, Germany beer.
Finally, brewers mashed porter in the 1700s for a lengthy period. William Ellis, in the London and Country Brewer, speaks of three hours in total, albeit some new malt is added, “capping” as it was termed. Still, that’s a long time, today most brewers can mash in one hour or half that time. The prolonged mashing assisted I believe the low enzyme malt to complete its conversion work.
The upshot: the reversal in timing of the popping phase can be explained by the switch from all-brown malt to mixed mashes benefitting from the high extract content of pale malt, and likely as well to shorter mash times after 1800.
Some other points that arise from the text: London used very little straw to kiln porter. Beer and ale in London were kilned from wood, certainly for porter, or some form of smokeless coal, e.g., culm, Welch coal, or coke. Straw was available at an acceptable cost too far from London, in “vales” where agriculture allowed its collection from stubble.
The Compleat Dealer did admire beer made from straw-kilned malt which he called “curious”. It means, here, distinctive and high quality. But little of it was actually used to make London porter, if you believe someone who started in the English malting business in 1810.