Salt and the salt industry

by Albert Frederick Calvert

“The third—52 by 26 feet and 13 inches deep holding 1464 cubic feet of Brine—burnt in 4 Furnaces in one week, 24 tons of coal and made 62 tons of salt.”

Chrysel is himself amazed that pans containing 360, 900, and even 1,400 cubic feet of brine can be boiled into salt in the same space of time, and he is feign to admit that “up to now, nobody, to my knowledge, has proved what length, breadth, and depth of pan is calculated to make the most salt with the least consumption of coal. Consequently everywhere are to be found many different pans, and other varieties are continually being tested. And I myself cannot feel that I am capable of deciding the question, nevertheless I will, from my experience and conscientious conviction, say what I consider is the best, cheapest, and most reliable pan for this purpose.”

After long search, and close inquiry in numerous salt-works, and as the result of his study of salt-making in pans of every size, Chrysel came to the conclusion that a single pan—“26 feet long, 18 feet broad, and 12 inches deep, with two furnaces, in a roomy salt-works with sufficient room for the workmen and baskets on both sides of the pan”—was to be preferred to all others. But this considered judgment was amended after further application to the problem by advocating an increase in length without changing the breadth of the pan. His ultimate verdict was in favour of a pan 52 ft. long, 18 ft. broad, and 1 ft. deep, with a capacity of 936 cubic feet of brine, equipped with two furnaces, and he declared that this pan, producing about 638 cwt. of salt per week, at a cost of £10 5s. 6d. for fuel, and selling for £127 15s. 6d., and giving a profit of £117 10s. was “the perfect article.”

Although, as I have pointed out, Chrysel’s patent was principally concerned with the arrangement of the brine pans, which were so arranged as to obtain the maximum amount of heat from the fuel consumed in the furnaces, in the course of his experiments he evolved an improved, if by no means a perfect, furnace. The peculiar nature of the superiority effected was based on the common knowledge that it is the natural tendency of fire heat and smoke to escape into the open air and disappear. He proceeds: “If, however, they are confined and shut up in a furnace under a salt pan they still require an opening to escape to the chimney else the fire cannot burn and is extinguished. If however the opening and place of exit into the draughts and chimney is too large and wide, as it is generally, and particularly under salt pans, not only will the draught of Air cause Wood and Coal to be more rapidly consumed and changed into Ashes which will choke the fire but also the fireheat and smoke will, by the draught of the air, hasten into the draughts and chimney, and the bottom of the pan will hardly be touched and scarcely half the work be done. On the contrary, if the opening and exit into the draughts and chimney has a proper proportion, according to the different sizes of the Pans and to the requisite Fire in the Furnace under the pan, the Fireheat and Smoke will be longer contained under the pan and that, steadily coming from the Furnace, will be increased and strengthened, so that double work under the pan will result, and wood or coal will not so rapidly be burnt to ashes but last longer and consequently do more work. All that is required in this is to calculate the mathematical proportion between the different sizes of the pans, the Furnace and the Fires and between the opening and Exit into the draughts and chimney, and to apply it.”

It will be recognized that both Lowndes and Chrysel were on the way to the solution of the problem of the perfect salt-making plant when they devoted themselves to the improvement of the furnace, but another century and a half was to elapse before the secret that eluded their efforts should be revealed. The luckless Furnival, some fifty years later than Chrysel, approached nearly to the goal to which they were all striving, and he, in common with his forerunners, had his share of the savage jealousy and persecution that the salt-men have ever visited upon those who venture into the lists with them. “No malice has been wanting to bring a disreputation upon my salt; and every wicked art will be practised to render its virtues ineffectual. The Salt Commissioners are my avowed enemies; for the miscarrying of my attempts will be their gain.” Thus wrote poor Lowndes, and Chrysel had similar grounds for complaint. “Before the above proof (the result of his experiment at Bye Fleet) was made openly, nobody believed in the anticipated saving,” he says, “but everybody doubted and some declared it to be impossible. After, however, the thing was made known, everybody on the contrary was in a state of wonderment. In a short time wonder was changed into envy, ill-will and malice, and many attempts were made to suppress me and destroy my patent, although it was not possible for any one to point out any failures or errors.” We shall see presently how the salt-men dealt with their successor, William Furnival.

Henry Holland, writing in 1808 on “The Production of Salt Brine,” furnishes some reliable details concerning the manufacture of brine-salt as it was conducted in Cheshire at the beginning of the nineteenth century. According to this authority: “The pans used in Cheshire, for the evaporating of the brine, are now made of wrought iron. The dimensions of these vary very much; but, in general, those of modern erection are considerably larger than what were in use a few years ago; and they usually contain from 600 to 800 superficial feet. One or two pans of still larger dimensions have been erected, each containing nearly 1,000 feet. Their usual form is that of an oblong square, and their depth from 12 to 16 inches. To a pan containing 600 to 800 superficial feet, there are usually three furnaces, from six and a half to seven feet long, and 20 to 24 inches wide. The grates are from two and a half to three feet from the bottom of the pan. The furnace-doors are single, and there are no doors to the ash-pits.

“The different pans are usually partitioned out from each other, and there is a separate pan-house to each pan. Within this pan-house, at one end is the coal-hole; the chimney occupies the other end, there is a walk along the two remaining sides of the pan, five or six feet wide; and between these walks and the sides of the pan-house, which are generally of wood, long benches four or five feet wide, are fixed, on which the salt is placed in conical baskets to drain after it has been taken out of the pan; a wooden or slated roof is placed over the pan-house, with louvres to allow the steam to pass freely out.

“The manufacture is conducted in several different ways, or rather heat is applied in various degrees, to effect the evaporation of the water of solution; and according to these different degrees of heat, the product is the stoved or lump salt; common salt; the large grained flaky; and large grained or fishery salt.”

In the making of stoved salt, the brine was brought to a boiling heat—which in brine fully saturated is 226 degrees of Fahrenheit—and the pan was twice filled in the course of twenty-four hours. In the making of common salt, the brine was first brought to boiling heat, for the double purpose of expediting saturation and clearing the brine of any earthy contents, and then, moderating the fires, the process of crystallization was completed with the brine heated to 160 or 170 degrees of Fahrenheit. The pan in which common salt was made was filled only once in twenty-four hours. The large grained, flaky salt was made with an evaporation conducted at the heat of 130 or 140 degrees, and the pan was filled once in every forty-eight hours; while in the case of fishery salt, the brine was brought to a heat of from 100 to 110 degrees of Fahrenheit, and five or six days were required to evaporate the water of solution. In the course of these several processes, various additions were often made to the brine, with the view of promoting the separation of any earthy mixture, or the more ready crystallization of the salt. These additions varied in different works, and many of them seem to have been made from ill-founded prejudices without any exact idea as to their probable effects. The principal additions made at various times were acids, animal jelly and gluten, vegetable mucilage, new or stale ale, wheat-flour, resin, butter, and alum.

Holland believed that the addition of acids to the brine was an innovation based upon the mistaken idea that the use of acid accounted for the superiority of the Dutch salt, but at the time at which he wrote the practice had been discontinued in Cheshire. Animal jelly and gluten for clearing the brine and promoting the separation of the earthy contents, were much used in preference to blood, which, while excellent for the purpose when fresh, was difficult to procure in sufficient quantity and to preserve from putrefaction. White of eggs, glue, and jelly procured by boiling cows’ and calves’ feet, were also found to answer perfectly well for the purpose of clarifying brine, but the use of new or stale ale and beer grounds as a brine clarifier, had been abandoned as inefficacious by Cheshire salt-men. Dr. Brownrigg was of opinion that salt-boilers had little to plead in favour of the addition of butter during the evaporation process, beyond immemorial custom, but Holland considered the salt-makers had ample grounds for their belief that butter assisted the granulation of the salt and made the brine “work more kindly.” On the question of the addition of alum opinions varied. Lowndes ascribed the superiority of his salt to the use of alum, but Brownrigg declared that “the goodness of Mr. Lowndes’ salt does not seem to be owing to the alum with which it is mixed, but may be attributed chiefly to the gentle heat used in the preparation.”