Not having anything better to do (I've been at home sick), I've been idly flicking through my collection of brewing manuals looking at the chapters on boiling. Who says I don't know how to employ my time usefully?
My interest has been spurred by the general lack of anything on hop additions in brewing records. (Except for good old Barclay Perkins.) Let's see what various authorities recommended. We'll start with one of my favourite, H Lloyd Hind:
The required quantity of hops is usually weighed in the hop store and brought to the copper side while the wort is running in. They may all be added at once, shortly before the commencement of boiling, or in two or three portions at different times. Thus, one half may be added at the start, with one quarter after boiling for half an hour or an hour, and one quarter half an hour before turning out. This process is somewhat wasteful, in that all the useful constituents may not be extracted from the last portion, but it is considered in some breweries, though not in all, to give a better flavoured beer on account of the reduced loss of volatile oils.
According to Chapman, about 80% of the oils is volatilised with the steam when hops are boiled for half an hour with water, the remaining 20% being converted to slightly soluble resins. These have no antiseptic properties but retain some of the original flavour of the oils which is communicated to the wort.
If the worts are collected in more than one copper at different gravities, the hops are divided in proportion with the lengths and gravities, allowance being made for different types of beer in parti-gyles. The period at which the hops arc added and the hop rate also influence the quantity of protein coagulated. For example, Kulbach and Wilharm found 0.89 mgm. of coagulable nitrogen still remaining in 100 ml. of boiled wort to which 4 lb. per barrel of hops were added at the commencement of boil, compared with 1.69 mgm. when two-thirds of the hops were held back until a quarter of an hour before turning out."
"Brewing Practices" by H. Lloyd Hind, 1940, pages 685-686.
So Lloyd Hind goes for three additions: at the start of the boil, one hour in, and half an hour before the end.
Next here's a somewaht older source:
That's nice and consistent. Wright chooses for three additions, too. Start, middle, 30-40 minutes before the end.
I myself, however, at all events when dealing with a somewhat extractive water, do not care about having any of the hops in before the copper length is made up, and then I should divide them into three portions, boiling one portion all the time, and the other portions less; the last portion, which consists of the best hops used, being only in the copper 30 to 40 minutes. And I have known good results in point of flavour come from simmering but not boiling (the copper, if a fire one, being actually "damped down'), this last portion of the hops, and this is especially to be recommended where circumstances allow of all the first copper hops being returned. That is not always the case by a very long way, even when there is no apparent reason to account for the fact. Hops, when added to a boiling copper, should be roused in to prevent the volatilisation of their essential oil before they get submerged. Volatile as this oil is, there seems reason to suppose it less readily driven off when diffused through the wort."
"A Handy Book for Brewers" by W.E. Wright, 1897, pages 317-318.
Oh, and he confirms what "make up" is: when the copper is being filled with wort. Boiling all the hops for the whole of the boil of the first copper, then boiling them again for the whole of the second boil sounds a bit crap. Obviously a technique of cheapskate brewers.
More of this tomorrow. Unless I get Courage's WW I grists finished first.