Salt and the salt industry

by Albert Frederick Calvert

On the subject of the supply and quality of the brine obtained at Nantwich and Middlewich, Dr. Jackson explains that the springs are rich or poor in a double sense, as a spring may be rich in salt but poor in the quantity of brine it affords. Thus, the chief pit at Middlewich contained a rich brine yielding a full fourth part of salt, but the supply was so meagre that the inhabitants were “limited to their proportions out of it,” and their requirements were made up out of pits furnishing a weaker brine. The pit at Nantwich was so plentiful as to supply all the salters, but while the brine contained only a sixth part of salt, “such quick use of it extremely strengthens the brine, perhaps to a degree little less than that of Middlewich pit.” In support of this statement that freshly drawn brine is richer than the liquor that has stood for some days in the pit, Dr. Jackson testified, as the result of personal experiment, that “a quart of brine, when the pit has been drawn off three or four days first, to supply five or six wich-houses, has yielded an ounce and a half more of salt than at another time, when it has had a rest of a week or thereabouts.”

In the Droitwich locality of Worcestershire, the quality of the brine closely resembled that of the Cheshire salt springs. In the account by Dr. Thomas Rastel, published in 1678 in the Philosophical Transactions, the writer says: “In the great pit at Upwich, we have at once three sorts of brine, which we call by the names of first-man, middle-man, and last-man, these sorts being of different strengths. The brine is drawn by a pump: that which is in the bottom is first pumped out; which is that we call first-man, etc. A quart measure of this brine weighs 29 ounces troy, but of distilled water only 24 ounces. This brine yields about a fourth part of salt; so that four tons of brine make about a ton of salt. The other two sorts less, or 28 ounces. And the pit yields 450 bushels of salt per day. In the best pit at Netherwich a quart of brine weighs 28 ounces and a half; this pit is 18 feet deep and 4 broad, and yields as much brine every 24 hours as makes about 40 bushels of salt. The worst pit at Netherwich is of the same breadth and depth as the former: a quart of brine out of which weighs 27 ounces and yields as much brine daily as makes about 30 bushels of salt.”

Although Dr. Rastel’s account of the salt-making methods in use at Droitwich coincides with that employed about the same period in Cheshire, he explains one or two minor variants and the reason of their adoption. “The vats we boil the brine in,” he writes, “are made of lead, cast into a flat plate 5 feet and a half long and 3 feet over: having the side and ends beaten up, and a little raised in the middle, which are set upon brickwork called ovens, in which is a grate to make the fire on, and an ash-hole which we call a trunk. In some seals are 6 of these pans, in some 5, some 4, some 3, some 2. In each of these pans is boiled at a time as much brine as makes 3 pecks of white salt. For clarifying the salt we should have little need, were it not for dust accidentally falling into the brine. The brine of itself being so clear that nothing can be clearer. For clarifying it, we use nothing but the whites of eggs, of which we take a quarter of a white, and put it into a gallon or two of brine, which being beaten with the hand, lathers as if it were soap, a small quantity of which froth put into each vat raises all the scum, the white of one egg clarifying 20 bushels of salt, by which means our salt is as white as anything can be: neither has it any ill savour, as that salt has that is clarified with blood. For granulating it we use nothing at all, for the brine is so strong of itself, that unless it be often stirred, it will make salt as large grained as bay-salt. I have boiled brine to a candy height, and it has produced clods of salt as clear as the clearest alum, like Isle of May salt: so that we are necessitated to put a small quantity of rosin into the brine, to make the grain of the salt small.”

“If it is asked why we use not iron pans as in Cheshire,” Dr. Rastel concludes, “I answer there have been trials made of both forged iron pans and cast iron. The former the strength of the brine so corrodes, that it quickly wears them out, the latter the brine breaks.”

The first serious attempt to effect a real improvement in the making of salt from brine was communicated to the Lords of the Admiralty in 1746 by Thomas Lowndes, and under the title of “Brine Salt Improved or the Method of Making Salt from Brine, that shall be as good or better than French Bay-Salt.” It was published in the same year in a handsomely printed, block-type brochure of 40 pages by S. Austin, of Newgate Street, Lowndes, who had spent his infancy in Middlewich and had acquired in his youth a thorough acquaintance with the Cheshire manner of salt-making, employed several years in travelling in France, during which he studied the process employed in the making of salt by solar evaporation from sea-water in the neighbourhood of Rochelle. At this time the bay-salt of Rochelle was regarded by merchants, victuallers, and fishermen as the best in Europe. He afterwards visited Holland for the purpose of ascertaining why the Dutch white herrings were superior to those cured in England, and he learned that the cause was explained by the method employed by the Dutch in purifying their salt. Armed with the knowledge he had acquired in France and Holland, and allowing for the difference between the French, Dutch, and English brines, Lowndes offered to enter into an agreement with the Admiralty to supply them with a better article than the French bay-salt, made by the following process—

“Let a Cheshire salt-pan (which commonly contains about eight hundred gallons) be filled with Brine, to within about an inch of the top; then make and light the fire; and when the Brine is just lukewarm, put in about an ounce of blood from the butcher’s, or the whites of two eggs; let the pan boil with all possible violence; as the scum rises take it off; when the fresh or watery part is pretty well decreased, throw into the pan the third part of a pint of new ale, or that quantity of bottoms of malt-drink; upon the Brine’s beginning to grain, throw into it the quantity of a small nutmeg of fresh butter; and when the liquor has sailed for about half an hour, that is, has produced a good deal of Salt, draw the pan, in other words, take out the Salt. By this time the fire will be greatly abated, and so will the heat of the liquor. Let no more fewel be thrown on the fire; but let the Brine gently cool, till one can just bear to put one’s hand into it; keep the Brine of that heat as near as possible; and when it has worked for some time, and is beginning to grain, throw in the quantity of a small nutmeg of fresh butter; and about two minutes after that, scatter throughout the pan, as equally as may be, an ounce and three quarters of clean common Allom pulverized very fine; and then instantly, with the common iron-scrape-pan stir the Brine very briskly in every part of the pan, for about a minute; then let the pan settle, and constantly feed the fire, so that the Brine may never be quite scalding hot, nor near so cold as lukewarm; let the pan stand working thus, for about three days and nights, and then draw it.

“The Brine remaining will by this time be so cold, that it will not work at all; therefore fresh Coals must be thrown upon the fire, and the Brine must boil for about half an hour, but not near so violently as before the first drawing; then, with the usual instrument, take out such Salt as is beginning to fall, (as they term it) and put it apart; now let the pan settle and cool. When the Brine becomes no hotter, than one can just bear to put ones hand into it, proceed in all respects as before; only let the quantity of Allom not exceed an ounce and a quarter. And in about eight and forty hours after draw the pan. ”

This process, as will be seen, involved the use of much slower fires than were usually employed in Cheshire, and allowed the liquor to simmer instead of boiling for a longer period. For this purpose, Mr. Lowndes proposed to use a large proportion of cinders in his furnaces, “since long boiling with great fires not only deprives salt of its spirit and strength, but causes its grain to become loose and soft, since cinders are better than coals in preserving a constant, equal, and gentle heat.” In order to correct the ill-effects suffered by the salt through being made in an enclosed, intensely hot room, filled with steam and smoke, he had recourse to the use of alum, which, he claimed, would restore to the salt its “natural cubical shoot and give it a proper hardness.” He further claimed that by this process the hot-houses or drying-houses could be dispensed with, waste in carriage would be avoided, and the pans would last three times as long; while, in order to anticipate the inevitable objections of the salt-makers and dispel the pretended difficulties that the workmen would find in executing his directions, the inventor explained that he had been careful to accommodate his process, as near as possible, “to the present practice in Cheshire.”

At the request of the Admiralty, the College of Physicians conducted several examinations of salt made by the Lowndes process, and reported that it was “in all respects, a strong and pure salt, equal at least, if not preferable to any we are acquainted with.” On the strength of this testimonial, Mr. Lowndes applied to the Admiralty to allow him a six months’ trial to prove the goodness of his salt for domestic purposes, twelve months to prove its excellence for the purpose of the Fishery of America, and two years in which to prove its efficacy in preserving beef and pork for the Royal Navy. If in this series of tests it should be proved that salt made by his process equalled French bay-salt, he proposed that they should pay him a total sum of £7,000, and should the trials demonstrate the slightest inferiority, he would be content to make his country a present of his labours. When the Admiralty declined to enter into negotiations with him, Mr. Lowndes laid his scheme before the House of Commons, which petitioned the King to instruct the Admiralty to make the tests on the inventor’s terms, but the sudden death of Lowndes in 1748 closed the controversy.

But the determination to bring the art of salt-making to “greater perfection” was not abandoned, although, as Dr. William Brownrigg admitted, the success achieved by Thomas Lowndes was thought by some people “to supersede the necessity of any further attempts for improving or extending our salt manufacture.” Brownrigg commended Lowndes’s method and testified to the purity and strength of his salt which had been exhibited before the College of Physicians, but he maintained that by other methods a purer and stronger salt might be made at a less expense. In point of fact, Dr. Brownrigg’s objection to the Lowndes’ method was that it was applied only to salt made from brine, or a solution of English rock-salt often prepared with impure water, and that the salt so produced, in his opinion, was inferior to marine salt. Brownrigg, only half realizing Lowndes’s intention, would appear to have grasped the fact that his process aimed at economy of fuel combined with uniformity in the degree and distribution of heat, but he does not seem to have appreciated the value of the improvement anticipated therefrom.