The following passage gives a very different reason for IPA being the strength it was:
"ALE, PALE OR BITTER; brewed chiefly for the Indian market and for other
tropical countries.—It is a light beverage, with much aroma, and, in consequence of the regulations regarding the malt duty, is commonly brewed from a wort of specific gravity 1055 or upwards; for no drawback is allowed by the Excise on the exportation of beer brewed from worts of a lower gravity than 1054. This impolitic interference with the operations of trade compels the manufacturer of bitter beer to employ wort of a much greater density than he otherwise would do; for beer made from wort of the specific gravity 1042 is not only better calculated to resist secondary fermentation and the other effects of a hot climate, but is also more pleasant and salubrious to the consumer. Under present circumstances the law expects the brewer of bitter beer to obtain four barrels of marketable beer from every quarter of malt he uses, which is just barely possible when the best malt of a good barley year is employed. . With every quarter of such malt 16lbs. of the best hops are used ; so that, if we assume the cost of malt at 60s. per quarter, and the best hops at 2s. per lb., we shall have, for the prime cost of each barrel of bitter beer—in malt, 15s.; in hops, 8s. ; together, 23s ; from which, on exportation, we must deduct the drawback of 5s. per barrel allowed by the Excise, which brings the prime cost down to 18s. per barrel, exclusive of the expense of manufacture, wear and tear of apparatus, capital invested in barrels, cooperage, &c., which constitute altogether a very formidable outlay. As, however, (his ale is sold as high as from 50s. to 65s. per barrel, there can be no doubt that the bitter ale trade has long been, and still continues, an exceedingly profitable speculation, though somewhat hazardous, from the liability of the article to undergo decomposition ere it finds a market."
"Ures' Dictionary of Arts, Manufactures and Mines" by Andrew Ure & Robert Hunt, 1867, Page 306
A word of explanation. "Drawback" was the money refunded to a brewer when beer was exported. The idea being that excise duty was only payable on beer consumed in the UK. It was a bit complicated in the period 1830-1880 because there was no tax as such on beer. It was the raw materials, malt and hops, which were taxed. Hence working out how much tax had been paid on a particular barrel of beer wasn't easy. So instead there was a simple flat-rate refund.
Anyway, what Ure is saying is that it made no financial sense for a brewer to export an IPA with a gravity lower than 1055, as he wouldn't get his 5 shillings a barrel back from the taxman. He implies that without this rule, the gravity of export IPA would have been lower.
I'm intrigued by his assertions that a Pale Ale with an OG of 1042 would survive the journey better and be more suited to the tropics.
- IPA, at around 1060, was an ordinary strength beer
- it would have been weaker, but for the tax regime
- its gravity didn't help it survive the voyage