"Turning now to the production of beers for home consumption, there can be no doubt about the advantage which accrues from a trade which is sufficiently extensive to admit of the brewing of special gyles for bottling. The brewer who is obliged to bottle his ordinary beers is generally seriously handicapped in comparison with his larger and more fortunate competitors. It does not of course follow that the productions of a brewery intended for cask trade are always less suitable for bottling; but, as a rule, a beer intended for this branch of the trade may be considerably improved by slight modifications, which would either not pay in the case of the ordinary cask beers, or which might actually prove undesirable. Some brewers who brew specially for bottling take the opportunity of reducing gravities slightly in comparison with cask beers, but this is not always wise. In many trades it happens that the taste in bottled beers is quite distinct from that in cask beers. The popular palate in respect to the latter may be in favour of a somewhat sweet, or only slightly bitter, ale, whereas the chief characteristics required in the bottled ales are possibly fine hop character, as well as practical immunity from sediment.
There is no doubt that as a general rule beers, both ales and stouts, which are intended for bottling, need more hops than are required for the same qualities consumed from the cask. We all know that, apart from any question of flavour bottled beers are particularly prone to the disease of ropiness, which of all beer diseases does more harm to a trade than any other. We also know perfectly well that the only natural and effective antidote is the hop, and that, however cleanly we may be in our production, we cannot hope for perfect safety with an insufficient percentage of this material.
Confining ourselves for the moment to the production of the highest qualities of bottling pale ale for home consumption, such as those of the best known Burton firms, or beers of similar character, it is obvious that perfection is only attained by the use of the very best materials, followed by sufficient maturity in cask and natural clarification before the ales are bottled. Indeed, one can go further and maintain that the very best results can only be obtained from season-brewed beers. It is admitted, of course, that in many parts of the country the popular palate is incapable of appreciating the perfection of quality that is thereby developed, and that consequently it seldom pays to lock up capital so long. But there are some highly successful firms who make a practice still of bottling season-brewed ales in the slacker months of the year, so that they may rely upon thorough maturity and perfection during the summer.
Besides the question of hopping, which is of special importance in regard to both copper and casks, that of attenuation is also of particular consequence in the production of all kinds of beer for bottling. Ales, such as we have just been considering, which will be allowed ample time to pass through all the desirable phases of secondary cask fermentation, may naturally rack rather higher than those which will have to be bottled within a few weeks of their brewing. It is of course impossible to lay down, or to suggest, any hard and fast rule on account of the variations of materials and surrounding conditions; but most brewers will agree that about a fifth of the original gravity is usually a desirable point to be aimed at."
"The bottling of English beers" by Arthur Hartley, 1906, pages 23 - 26.
Special gyles for bottling. They certainly existed amongst London brewers. The earliest one I can identify is Truman's Bottling Keeping Porter from 1840. As you cvan see from the table below, it was indeed more heavily hopped. At more than double the rate of the standard draught Running Porter.