Grantville Gazette, Volume 40 (36 page)

Perlite-in-vacuum is "the commercially accepted standard in the liquid hydrogen industry," and you can get away with a 0.1 torr vacuum, yielding a conductivity of
0.018
. (Brewer 327).

Expanded perlite is a volcanic glass that contains water and therefore pops like popcorn when quickly heated above 1600
^o
F. In 2009, the principal producers of perlite were Greece*, United States (New Mexico*, Nevada*, California*), Turkey*, Japan, Hungary*, Italy, Mexico, Georgia, Armenia, Iran, Slovakia, Australia, the Philippines and Zimbabwe. There is also perlite in South Africa, Algeria, Bulgaria, China, Cyprus, Iceland, Morocco, Mozambique, and Russia. (Index Mundi). A few of these sources (asterisked) are mentioned in the modern
Encyclopedia Britannica
, which draws particular attention to the island of Melos and to Kremnica in central Slovakia.

Diatomaceous earth (
kieselguhr
) are fossilized diatoms, and was discovered in 1836 on the Luneburg Heath, north Germany (Wikipedia/Diatomaceous earth). EB11/Diatomaceae remarks on the size of the deposit at Richmond, Virginia, and other entries mention deposits at Llyn Arenig Bach (Merioneth, North Wales) and between Logie Coldstone and Dinnet (Aberdeenshire, Scotland). Modern EB mentions Old World deposits in Iceland (LakeMyvatn), Denmark, France, Russia and Algeria.

Evacuated foam rubber and plastics have also been developed, but those mentioned by Perry aren't as good insulators as the evacuated powders already discussed.

In 1951, "superinsulation" was developed; this inserts a multitude of "floating" (minimal wall contact) reflective panels (aluminum foil or aluminized Mylar) into the hard (10
^-4
required) vacuum space, reducing radiative heat flow. Conductivity at cryogenic temperatures may be as low as
0.0003
. (Perry 12-36, Marks 19-35).

Transporting Ice

Ice is a bulk commodity (low price per unit volume) and hence is economically transported for long distances only by water or by railroad.

By water
. When Frederic Tudor (1783
–
1864), the "Ice King," first proposed that one could make a profit selling ice in the Caribbean, the reaction he received was one of almost universal incredulity. To make matters worse, he wasn't able to simply to rent cargo space on someone else's ship, because the shipowners feared that the melting ice would sink the vessel. Hence, he had to buy his own ship, a brig, for $4750 (Weightman 37).

There were, in fact, two problems with carrying ice by sea. First, the ice would initially act as ballast, but as it melted and drained away, the ship would become lighter and harder to handle. This wasn't just because of the loss of ballast, but because the ice could shift around once its volume was reduced. You want a stout ship and an expert crew. Secondly, the meltwater could ruin other cargo. (Weightman 27, 33; Blain 8). Obviously, the problems are minimized if you keep melting to a minimum, which is also desirable from the standpoint of having cargo to sell at the destination.

In the New England ice trade, shipments to the West Indies, which could be reached in just ten or fifteen days, didn't require extensive insulation. The hold was lined with insulation, say, four inches of tan bark [a waste material from tanner's pits] on bottom and sides, and then the ice was packed in and covered with hay. The hatches were kept closed until voyage's end. (MM).

We have several descriptions of how Frederic Tudor had the
Tuscany
loaded for its lengthy voyage to Calcutta. Tudor first laid "a sheathing of boards one inch from the skin of the vessel." I think that means that he left an air space. Then he covered that with "6 inches tan [bark]." And that in turn was covered with one foot boards of lumber. Note that the result was a double-walled bottom. On this he loaded 180 tons of ice. His crew rammed in first 6 inches of hay and then one foot of tan bark on the sides. And finally, "a foot of tan or perhaps 20 inches" was laid on top "to make an unbroken stratum on top ends, sides and bottom." (Weightman 126). His expectation was that the ice "would melt at a rate of about fifty pounds an hour over the four-month voyage," so that two-thirds would make it to Calcutta.

As Weightman comments, the crew would be instructed not to open the hatches (and thus expose the ice to the air), and it would be expected to continuously pump out the meltwater (and of course any seawater that made it into the hold). However, we don't have any details about the pumping arrangements.

A somewhat different description is given by Dixwell (MM). This says that the ice hold was fifty feet long, beginning at the after part of the forward hatch, and that it was essentially an ice house, with two walls of one inch deal planks and one foot of tan in-between, on bottom, top and sides. "The pump, well, and main-mast, were boxed round in the same manner." The blocks were packed inside, without intervening spaces; the top was laid down, and then a foot of hay was placed over it. The underside of the deck was planked with deal and any remaining air space was filled with tan.

An interesting feature was an "ice gauge," "a kind of float" embedded in the ice so its subsidence could be measured (presumably only on arrival, because the hold was supposed to remain closed en route). This didn't work too well, because the ice melted between the blocks as well as on top. Nonetheless, the supercargo estimated that the loss in the four month seven day passage was 55 tons. Note that 6
–
8 more tons were lost ascending the river and another 20 in porting the ice from the ship to the local ice house.

It is very unlikely that anyone in Grantville in fact knows anything about how ice was shipped, so they are in fact starting from scratch. They will certainly realize that it's important to keep the ice insulated, and they will also recognize that despite best efforts, the ice will melt and they will have to get rid of the meltwater. It's less certain that they will have foreknowledge of the effect of melting on ship stability; there might be an interesting plot twist there.

The loss of ice in transport will be dependent on the same factors as for stored ice. For shipments from the northern USA to the Gulf States, it typically ran 25
–
30% (Hall 35). Even in New York, 25
–
33% loss was expected (27), and Cincinnati suffered 33% (31).

By rail
. Ice was also, occasionally, transported by rail. "In 1878, "four freight trains of 20 cars each were loaded with [Maine] ice at $1.50 per ton and dispatched to Saint Louis, where they delivered in good condition 672 tons out of a total shipment of 1,275. The freight cost $5.85 per gross ton, and the ice sold for $10.50 per net ton. Owing to the waste of 50 per cent, the venture netted a large loss, and was not repeated." (Hall 21).

However, inland cities without a good river connection would have to be serviced by rail. Northern ice was shipped by rail from Savannah to Macon and Atlanta (Hall 35). Ice was also carried by rail from Quincy, Illinois to points in Texas, 5
–
7 days journey. (Id.), and from Sandusky to Columbus, Springfield and Cincinnati (32).

There were two basic problems with rail transport. First, while it's cheaper to ship by rail car than by truck, wagon or pack mule, the river barge, sailing ship, or steamship is cheaper still. See Cooper, Hither and Yon (
Grantville Gazette
11).

Secondly, a rail car might hold 40 tons of ice, as compared to the 100 or more tons in the hold of a ship. The surface area/volume ratio is higher for the rail car, so the percentage daily loss by melting will be higher, too, unless it's more heavily insulated.

Refrigerated Transport of Perishables

The ice, instead of being the shipped commodity, may simply be a means of keeping perishable foods cool and therefore fresh until they reach the destination. While refrigerated transport still needs insulation to protect both ice and commodities from ambient heat, they must be designed to encourage heat flow from the perishables to the ice . . . preserving the former at the cost of the latter.

If natural ice isn't cold enough, brine can be frozen instead. That doesn't necessarily mean using artificial refrigeration, the brine could be set out in bins overnight in a place and season where the temperature falls low enough to freeze it.

Rail Transport
. The first successful use of natural ice refrigeration on a railroad car was in 1842, but the Western Railroad of Massachussetts. This was, strictly speaking, a climate-controlled double-walled car; it used ice in summer and powdered charcoal in winter.

Perishable cargo could be carried in individual iced containers on a standard boxcar. Parker Earle's 1866 strawberry express trains were loaded with ice chests having ice on the bottom and berries above. (White 273).

But as I said previously, bigger is better, and so there are advantages to refrigerating the entire car. In 1883, a car cost about $500 (124), whereas a reefer cost $750
–
1200.

Several different layouts were experimented with. Lyman began reefer operation in 1853, and his 1860 cars had ice bunkers with roof hatches (for re-icing) at both ends, and an inclined floor with pipes to carry away meltwater. (272). The ice of course was crushed ice, that could be poured in through the hatch, rather than the large blocks of the ice trade.

In 1877, Tiffany patented a car with "a full length overhead ice bunker." This had a V-shaped bottom, so that meltwater was conducted into drainage pipes. These overhead bunker cars reportedly "used only half the amount of ice required by conventional end-bunker cars." (274
–
5).

Wickes' popular late nineteenth-century design (275
–
6) had a number of interesting features. His overhead ice tanks were surrounded by metal basketwork with projecting leaves; the latter increased the cooling surface. Also, wire was strung underneath the tank, making a close mesh. The theory was that the drip water would strike the wires and being broken into a fine spray, which—since the water was "practically as cold as the ice itself"—would further cool the perishables.

A third layout was introduced by Hanrahan (1890); his bunker was in the center of the car. That reduced the number of roof hatches needed, but the four side doors he provided ensured plenty of opportunity for warm air to leak in. (283).

It has proven surprisingly difficult to obtain reliable details of the design adopted by the meat packing king, Gustavus Swift, and designed by Andrew Chase. Many sources say that Chase's innovation was an overhead ice bunker, but of course that's wrong. One possibility is that Chase's "cold blast" refrigeration featured ice bunkers in the overhead corners. (Fields 105). Cold air would sink down the sides, and warm air rise in the center, thus providing greater air circulation than in the Tiffany or Wickes systems.

However, Chase U.S. Patent 346,354, REFRIGERATING BUILDINGS AND VESSELS (1886) depicts a system featuring a full-length overhead cooling chamber but with air gaps at the sides. The floor of the ice bunker has a downward projection at one side, creating a full-length passage for cold air to sink, and an upward projection on the other side, creating a passage for warm air to rise. As drawn, the cooling chamber was not an ice bunker, but rather contained coolant pipes that were connected with a mechanical refrigeration system.

In the nineteenth-century reefers, insulation was fairly primitive, with paper, wood, sawdust, cork, and dead-air space being typical. The early refrigerator cars had wooden bodies, and therefore numerous minute cracks. Ayers proposed the use of air-tight rubber sheets to block the entry of warm air and moisture. (278).

There are several model railroaders and railfans in Grantville, and it's difficult to predict just how much they would know about refrigerated cars. There are several truck drivers in town, and some may have driven reefer trucks.

Water Transport
. The down-timers realize that fish are extremely perishable, and have tried to cope with this in a variety of ways. In sixteenth-century Holland, some fishing vessels were equipped with "wet wells," enclosures so that the captured fish could be maintained alive in circulating seawater. However, this didn't work well for deepwater fish. (Kurlansky).

The Dutch also had
buizen
, "factory" ships on which captured fish were gutted, salted and barreled; these were periodically visited by fast
ventjagers
("sale-hunters") which would bring the barrels back to market so the
buizen
could remain at sea. (Sommerville). Tobias Gentleman described the Dutch system in 1614, but I think it dated back to the sixteenth century. (Poulsen 110ff).

While we aren't interested in wet wells or salted fish, the point is that there are going to be people who are keenly interested in preserving the catch.

Nonetheless, it wasn't until the 1780s that the British realized that fish could be chilled, with natural ice, for transport from Scotland to London, a six day journey on average. Until then, fish were carried in carts or on packhorses, and only during the cooler months; a sea passage by sailing ship could be delayed by winds and deliver only a rotten cargo. First, salmon were shipped in ice, then herring. Naturally, the introduction of the steamship made this even more efficient. (David 231ff).

British fishing vessels also started carrying ice, so that they could remain at sea longer and still return with fresh fish, which sold at a premium over salted fish. (238). Reportedly, the first use of this stratagem in the American fishing industry was by a Gloucester smack in 1838, to preserve halibut that had died inadvertently. (Stevenson 359).

Freshwater ice can only be used to bring fish just down to its freezing temperature, 0
^o
C. But fish will last longer, with good taste, if superchilled—brought to a temperature below zero but above the temperature at which fish muscle freezes. The critical temperature varies by fish species: haddock, -0.8 to -1
^o
C; halibut, -1 to -1.2; herring, -1.4. Superchilling can be achieved by freezing seawater ice or an artificial brine. (Huss).