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Cooking and Pressing
Cookers used steam to break down the herring's flesh and release the oil. Presses used high pressure to separate liquids from solids. The big cookers were long tubes. They had screw conveyors inside to move the fish through. The fish was fed from the bins into one end of the cookers and forced along the entire length. Steam jets kept up the heat and pressure all the way through. At the other end, the cooked fish mash dropped into huge presses.
Presses were like two large screws – one fast turning called the feed screw, the other slow turning called the pressure screw. The feed screw pushed the cooked fish mash deep into the press. There, the pressure screw forced it against finely perforated metal screens. Liquids were slowly squeezed out through the tiny holes. This created two distinct materials – liquid ‘press liquor' and solid ‘press cake' as they were called in the industry.
It was never easy being the Pressman. He kept the cookers and presses in good order. He monitored temperatures and checked steam levels to ensure that the press cake and press liquor were always the proper consistency for machines further down the line. Sometimes herring weren't the only thing unloaded into the bins and fed into the cookers. As former Pressman Everett Pierce recalled, "Gaff hooks and bolts were a real problem. They'd get into the presses and tear holes through the screens and you'd get meal in your liquor." Eventually, powerful magnets were placed just before the cookers to prevent this kind of problem!