If material is collected into alcohol and stored in bottles or jars it is often too bulky or heavy to transport easily. The bulk of any sample can be reduced quite dramatically by transferring the material to polythene bags, pouring off the excess alcohol and then sealing. Material can be stored in this way for a maximum of two or three weeks. Any polythene bags can used for this purpose but the best is a 11x21cm WHIRL-PAK® bag which is generally available from laboratory suppliers, particularly in the USA. WHIRL-PAK is best because it contains a built in "twist-lock" that allows the top of the bag to be rolled down and then locked in place using the "twist-lock" wire.
The method is as follows.
(1) Gently pour the sample into the polythene bag. It is important not to overfill the bag. The material in the sample should not fill more than the bottom 5-7cm of the bag, although the alcohol in the sample can fill half the bag. Do not forget to add a data label to the bag.
(2) Put the bag aside, upright in a suitable container and allow to settle for at least two hours, or even overnight.
(3) Gently pour of the alcohol from the bag, taking care not to pour off the smallest specimens, until about 2.5 cm of alcohol is left above the material. Put the top part of the bag on a horizontal surface (keeping the lower part containing the material vertical) and remove the air bubbles using the side of your hand or a straight object such as a pencil. Roll the bag down from the top and seal. If done well there should be no air bubbles, or hardly any, trapped in the top of the bag.
(4) Place this bag in at least one other polythene bag and seal.
(5) Store in an airtight plastic container.
Last updated 19-Aug-2003 Dr B R Pitkin