We know an awful lot about Porter, save the most tantalising fact: what it tasted like. Whilst we can research and recreate the techniques used to make Porter, sadly we cannot recreate the raw materials.
The defining ingredient of Porter was malt, although the malt grists changed drastically during the course of the eighteenth century. We know enough about the malting equipment and fuels to make a fair stab at replicating the malting regimes should we wish to – and we are indebted to those groups of devotees who attempt to do just this, in particular the Durden Park Beer Circle.
About barley growing we know a fair amount from many authorities.
“ On our Red Clays this Grain generally comes off reddish at both ends, and sometimes all over, with a thick skin and a tuff nature, somewhat like the Soil it grows in, and therefore not so valuable as that of contrary varieties, nor are the black, blewish and marley Clays of the Vale much better, but Loams are, and Gravels better than them, as all the Chalks are better than the Gravels; on these two last Soils the Barley acquires a whitish body, a think skin, a short plump kernel, and a sweet flower, which occasions those fine, pale and amber malts made at Dunstable, Tring and Dagnal.” ii
What none of us know, however, is what barley varieties were like in the 1700s. Similarly we can have no idea of the nature of the yeasts used at that time. They would have been far removed from our clean, single strain cultures of today, being a complex microflora of brewing yeasts, wild yeasts and bacteria. We have – unless someone wants to devote a lifetime - absolutely no method of unpicking all the scientific work on yeasts that has occurred since Louis Pasteur started looking at them through a microscope in the 1860s to come up with a yeast culture that would have been at home in a London Porter house.
Neither do we know much about the hops of the day. Varieties were unknown, outside those of strict geography, East Kent hops being early on regarded as superior for many purposes. Acid and lupulin levels were, of course, unknown (though clearly much lower than today) even if the principle reasons for the necessity of boiling hops in the wort were.
Finally
there must also be question mark over the influence of the major ingredient
in beer; water. Obviously the geology of London has not changed in
300 years, so perhaps this is the ingredient about which we can be
most confident, but we can still cannot perform a scientific analysis
on a modern water sample, be it from river, aquifer or well and compare
it with a sample from 1720.
In short, anyone attempting to replicate a London Porter of the eighteenth
century will have to make a number of assumptions and a number of departures
from modern brewing practices, as well as conduct much careful research,
in order to attempt a recreation of the style. The difficulty of
the task, however,
doesn’t make it unjustworthy. It merely increases the reward.
Enough then, of what we don’t know about Porter. Let us turn to what we do know.