SP Scientific Freezemobile Series, Operator'S Manual, Page: 30 / 54

Basic Operation VirTis Freezemobile 25L and 35L
20 Rev 005, 02/12
© SP Scientific 2012
13. After removing all product, press the DEFR button to enable condenser
defrost. The defrost function allows ice to be removed from the condenser
without fully melting. A drain line is connected to a plastic quick-connect
fitting, which acts like a valve. To open the valve, push the fitting into its
receptacle. To close the valve, press the small grey release button on the top
of the receptacle. The fitting will pop out.
Note: The quick-connect fitting must be closed prior to freeze-drying; if it is open the
appropriate vacuum pressure will not be achieved.
14. Once the ice has melted away from the condenser, the ice can be removed.
Thoroughly clean and rinse the condenser with a mild detergent or baking
soda solution (to neutralize acids).
Note: Do not chip away at the ice, as this may damage the condenser.
15. The defrost system turns off automatically after an hour. To disable it
manually, press the DEFR button.
Meltback
Products that have low freezing points are prone to meltback during the freeze-drying
process. Meltback is a term commonly used to describe when the product melts or
defrosts before sublimating. The following suggestions may help to prevent meltback:

Decrease the volume and depth of the product.

Insulate the product container to slow down sublimation caused by an
ambient heat source.

Decrease the amount of product or number of samples connected.

Verify that the equipment is functioning properly and ensure that room
temperature aids the air-cooled refrigeration system.

Consider diluting the product with water.
For products that dry readily, alternative heat sources such as a heat lamp may be
used to expedite the freeze-drying process.
Preventing Glassware Breakage

Avoid cleaning glassware with a wire brush as metal-to-glass abrasion
creates microscopic scratches which can cause breakage.

Never fill a flask to more than half of its total capacity (
e.g
., a 600 mL flask
has a working capacity of 300 mL).

When pre-freezing samples in a storage freezer, tilt glassware at a 30 to 45
degree angle to increase surface area and reduce stress on the glass.

To prevent glass-to-glass abrasion when placing flasks in glassware washers,
do not allow contact with metal racks or other glassware.