. The half-tone process. A practical manual of photo-engraving in half-tone on zinc, copper, and brass. onnect the whole, andso ensure the entrance to each room being in theshade. The ventilation of the dark room is a more impor-tant matter than most people appear to think. Notonly does a perfectly ventilated dark room add to thecomfort of the operator, butit also contributes in alarger measure to thesuccess of the delicate pro-cesses worked done in a properly-ventilated room maintainedat an even temperature willbe much more uniform thanit would be otherwise. Ventilators of the fo
. The half-tone process. A practical manual of photo-engraving in half-tone on zinc, copper, and brass. onnect the whole, andso ensure the entrance to each room being in theshade. The ventilation of the dark room is a more impor-tant matter than most people appear to think. Notonly does a perfectly ventilated dark room add to thecomfort of the operator, butit also contributes in alarger measure to thesuccess of the delicate pro-cesses worked done in a properly-ventilated room maintainedat an even temperature willbe much more uniform thanit would be otherwise. Ventilators of the formshown in fig. 28 can be pur-chased ready made in sheetiron with any desired length of piping, and furnish acheap means of ventilating a dark room. An electric fan is a luxury, but, nevertheless, anexcellent thing for keeping the dark room cool. It must be borne in mind that wherever there isa ventilating outlet there must be at some other pointan inlet for fresh air, and the most convenient wayof arranging this is to provide it in the lower partof the door by having a few holes bored through, and. 74 THE HALF-TONE PROCESS. an inner panel arranged so as to cover up the lightcoming through them without obstructing the passageof air. A Louvre ventilator—which is something like aVenetian blind—over the top of the door orwindow (if there is one) is a good arrangement forventilation, where the cowl-shaped ventilator cannot beused. A few holes or slots cut in the partition near theceiling, and covered with some skirting to cut off anystray light, is a more rough-and-ready means of venti-lating, which is used more often than not. The walls and ceiling or woodwork should be black,or of some dark shade which will not reflect straylight. Another matter to which attention must be paid inbuilding a dark room is in regard to the prevention ofdust, which occasions great difficulty in some effective way of minimising it is to cover all venti-lating apertures with something l
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