240 CURRENT TOHCS. [J. F. I.

Freezing vs. Dehydrating.--Manufacturers of frozen foods and of de- hydrated foods will compete sharply, it is expected, whenever conditions permit free use of all kinds of foods by civilians. Packaging, as well as the preparation of foods, is getting attention in research laboratories and by manu- facturers. At present each group is watching developments in packaging and is benefiting from experiments by the other group. U. S. Department of Agriculture scientists are active in both fields and encourage experiments in packaging. Frozen foods and dehydrated foods have one problem in common, the Agricultural Research Administration points out--control of moisture in the finished product. Food dehydrators need to keep moisture out--or their products will spoil. Food freezers need to keep moisture in, for even at zero storage there may be serious loss of moisture, and a loss of as much as 5 per cent. of the moisture in a frozen food lowers its quality. Both groups are working with the latest discoveries in plastic films that are not only waterproof in the ordinary sense, but also proof against the passage of water vapor. William Rabak of the Western Regional Research Laboratory reports that some of the most promising packaging materials are laminated, that is, made up of two or more sheets of moisture-proof material Cemented together by a plastic. Such an adhesive, he says, will not only bind the films together but it fills and closes any pinhole imperfections in the films. One of the most effective materials is composed of a thin lead foil attached on one side to laminated kraft paper and on the other to laminated moisture-proof cellophane cemented with a moisture-resistant adhesive.

R. H. O.

Glass Kite String Used for Box Kite for Radio Antenna.--A kite string of glass yarn is used with the box kite that carries aloft the antenna of the portable, hand generator, radio transmitter developed by the Army Air Forces to summon help for fliers forced to make crash landings at sea. The complete transmitter kit for use on aircraft life rafts includes the sending set, an ordinary cloth and wood frame box kite, an.antenna consisting of very fine copper wire wound around the glass kite string, two balloons and capsules of compressed hydrogen. The balloons, inflated with the hydrogen, can be used to carry the antenna aloft in the event of a calm. Glass yarn is used as the kite string because of its great strength in proportion to its weight, and because it will not rot or otherwise deteriorate from the effects of salt water, tropic sunlight, rain or dampness. The yarn is twisted and plied from continuous filament glass fibers which can be drawn to indefinite lengths, measurable in miles. The transmitter is so constructed that the operator needs no knowledge of radio or code. When the hand crank is used to generate power, the trans- mitter automatically grinds out the SOS signal on 500 kilocycles, the inter- national distress frequency.

R. H. O.