How did the ice plant make its portable blocks of coldness? The method was unexpectedly complicated.
Here’s the coldroom, where the compressed and relatively cool ammonia is allowed to relieve its pressure and absorb heat from the water that will become ice.
What’s going on inside? We have a grid in the floor, over a pool of cold brine kept at -10 degrees by the evaporation coils. The brine is also agitated by a stirrer, not shown here. Polistra is filling one of the cans with water.
I’ve shown only one filled row for simplicity. All rows in the grid were occupied by cans, immersed in the cold and moving brine. The movement insured that each can was cooled equally, and also helped to shake out the air in the cans. Clear ice was considered a mark of quality.
These are the smallest available cans, 8 x 8 x 32, holding 50 pounds of ice. Most systems used larger cans. Each can has a graspable edge on top, which is the key to the mass production process.
Picking up and handling the cans was difficult. Not necessarily from the weight, since a typical workman could handle 50 pounds. The problem was getting out onto the floating grid and grabbing the slippery can. Machines like this air-driven hoist did the grabbing job, and workmen handled the cans after they were on solid ground. The hoist has spring-loaded tongs designed to snap onto the top edge of the can, and mechanisms to lift the tongs and slide the carrier horizontally.
After taking the can out of the grid, the ice had to be pulled out. This machine, known as the Thawing Apparatus, did the job. A box holds the can tightly while warm water sprays on the surface.
After the can expands, the Thawing Apparatus can be tilted to let the ice slide out of the can. Then the can is dropped back into the grid and refilled for the next load.