Shell freezing is the classic method for preparing samples for freeze drying. Flasks are automatically rotated by motor driven rollers in a refrigerated bath containing alcohol or any other appropriate fluid. A thin coating of product is evenly frozen around the inside "shell" of a flask, permitting a greater volume of material to be safely processed during each freeze drying run. These automatic, refrigerated units provide a simple and efficient means of pre-freezing many flasks at a time, producing the desired coatings inside. One shellbath can be installed on a freezemobile 25 or 35 as an option.
One or two bath units can be mounted in a streamlined cabinet giving capacities up to two each 2000ml flasks at one time or six each 150ml flasks at one time.
Two motor driven stainless steel rollers rotate freeze drying flasks in the -50°C (or -75°C) bath and evenly distribute a thin coating of liquid product around the inside "shell" of the flask until it is solidly frozen. A greater volume of material may be processed during each freeze drying cycle, as shell freezing permits flasks to be filled half full with little increase in drying time because moisture does not have to migrate through the ice interface and a thick layer of dried product. Flask lift devices elevate flask caps, forming conical coating inside the flasks as they rotate, and preventing fouling of the lid, filter and stoppering plug.
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