Freeze-sterilisation is a conservation procedure. As such, it is essential to assess the condition of each object to be frozen and to consider the appropriateness of this procedure for each object. Not all objects can be safely frozen. It is strongly recommended that a conservator be consulted during the decision process. Once the decision has been made to undertake freeze-sterilization, preparation of the artefact, the temperature during the freeze process and the timing of the process are crucial for successful kills.

1. Determine, with the assistance of a qualified conservator, if the materials contained in the object and it's condition will allow a safe, controlled freezing procedure.

2. Place the object in a clear polythene bag, eliminate as much excess air from the bag as possible, either by partially vacuum aspirating the bag or by filling large void areas with a stable, moisture-absorbant material such as clean cotton wool. The bag must be tightly sealed so it is as airtight as possible.

3. Bagged infested material should be kept at room temperature (above 18 degrees Celsius) until placed in the freezer.

4. Place the bagged object in a non-frost freezer capable of attaining and holding a temperature of -20 degrees Celsius.

5. There should be enough air circulation around the bagged artefact in the freezer to allow it to cool to at least 0 degrees Celsius in no more than 4 hours.

6. Leave the artefact in the freezer for 5 to 7 days.

7. Remove the object from the freezer leaving the bag sealed and place it in a safe place for 24 hours to allow it to reach room temperature. A slow rate of thaw is desirable.

Alternatively: a slow thaw can be achieved by leaving the object in the freezer, turning it off and leaving it closed, allowing the temperature to slowly warm. If this method is used, great care must be observed to make sure that any condensing frost on the inside of the freezer has an unobstructed drainage route to avoid pools of water accumulating around the object. Once thawed, keep the object at room temperature for 24 hours without opening the bag.

A written record of all above procedures should be made and included with the condition report of the object. Freezing is a conservation treatment. Any treatment to an object requires thorough documentation.

Remember that freezing an object will kill off the current infestation but will not protect against reinfestation. A normal program of preventative insecticide protection should be carried out as soon as the object leaves the safety of it's plastic bag.