The entire virtue of the so-called electric annihilators for moistening the tympan of a press comes from the moisture they contain. Ordinary glycerin, which is cheaper, will answer as well. These applications are undesirable because they cause the packing to swell, and, in consequence, detract from the adjustment of the overlays.
There is a simple and not very expensive device on the market called the Thompson electrical neutralizer that has been found helpful. It is provided with a tinsel cord such as is used in decorating Christmas trees. The cord is stretched across the press so that the sheets are brushed by it as they pass to the delivery board, and are thus offered a connection whereby the static charges may escape into the ground. A second device of merit consists in a gas pipe with flames at frequent intervals over which the printed sheets pass in close proximity on their way to the delivery board.
The most successful neutralizer with which the writer is personally familiar is the Chapman. By means of an alternating current of electricity, it supplies through a special apparatus alternating discharges of positive and negative electric currents against the sheets of paper as they are carried along the press. In the presence of such a current the charges on the paper become their own destroyers, as they draw out of the alternating current only the kind and quantity of electricity which is sufficient for their complete neutralization.
There have been quite a number of other inventions, an account of which the writer published in The Printing Art, Vol. XIX, No. 1, March, 1912. All are based on one of the following principles:
1.—Making paper a conductor by moistening.
2.—Making the air a conductor by humidifying.
3.—Inducing static charges out of the paper by means of grounded wires or gas flames.
4.—Neutralizing the static charges in the sheet with charges of opposite polarity.
Another solution of this problem, as well as of the problem of expansion of paper and consequent poor register, could be reached by the construction of an insulated pressroom. The air for this room should be supplied through an apparatus in which it could be brought to any required degree of temperature and humidity. The paper would naturally have to undergo sufficient airing in such a room as to become acclimated. After that, if the conditions remained constant, there could be no difficulty in getting register, so far as the paper was concerned, and a proper amount of warmth and moisture would also dissipate all static electricity.
It is difficult to anticipate or to completely cover all conceivable paper troubles, and when some one which may not be diagnosed on the basis of the general principles enumerated, consultation with some paper expert should clearly be sought. The author will be glad to communicate on such subjects.