Invented in 1892 by Sir James Dewar, the double-walled cryogenic storage vessel known as a “dewar” revolutionized the cryogenic industry by allowing cryogenic media to be stored for longer periods of time. Though the concept didn’t change much over the years, the biggest innovation came in the form of multilayer insulation, which increased storage times dramatically and made the dewar the industry standard. (Incidentally, it was also discovered that the same construction also kept hot liquids hot, prompting the development of the modern thermos.)
Modern dewars are typically constructed with two or more layers to maintain a high vacuum between the layers and thus exceptional thermal insulation. The better the vacuum the longer the cryogenic medium is preserved.
Cryogenic liquids can refer to liquid oxygen, liquid helium, and liquid hydrogen, though liquid nitrogen is the most prevalent medium. With a boiling point of -196 degrees Celsius, liquid nitrogen is used across a wide range of lab settings for preserving biological specimens (like animal semen for breeding programs). Outside of the lab, liquid nitrogen can be used to shrink metal bearings in a fabrication application, cool rocket engines, and even to flash freeze novelty ice cream.
Ratermann’s extensive selection of lab and specimen dewars encompasses a variety of sizes and shapes, with lab dewar capacities ranging from 6 to 50 liters.
Both the lab and specimen dewars are true open-top dewars, meaning that as the cryogenic pressure builds, gas can vent through the open top or a loose-fitting lid. Ratermann has a selection of accessory lids and styrofoam cores, which pop-up if the pressure gets too high and vents excess gas. Rubber pour-spouts, dipper tubes and insulating jackets are also available.