The printing plate, or form of type, is locked up in a chase in the same way as any other form for printing. Gold size—a special printing ink having a “tacky” body, and usually light brown in color—is put on the press. If the run is to be a long one, say 5,000 impressions or more, the size should be applied by means of an ink fountain which will insure an even flow of color.
Making ready for a form of this class is not difficult. The tympan may consist of half a dozen sheets of news or book paper, a sheet of fuller board (or binders’ board), and one top-sheet of heavy manila paper. The fuller board should be placed directly under the Manila top-sheet, and the sheets of news or book paper should be placed underneath the fuller board. This is called a “hard” tympan, and it will give better results in the printing than a “soft” tympan. Start the make-ready with a weak impression, and then add sheets of news or book paper, underneath the fuller board, until the subject prints sharply and distinctly on the stock used for the wrappers.
Highly glazed paper is generally used for box-wrappers which are to be bronzed, and the heavy size will often “lift” or “pick” the glazed surface of the stock in printing. To overcome this trouble, add a few drops of boiled linseed oil to the size, or a few drops of 00 reducing varnish. Any of the printing ink manufacturers can supply a reducing preparation for this purpose. Only a few drops of the reducer should be added to a quantity of the size as the size will not hold the bronze powder when made too thin.
As the sheets are printed with the size, the bronze powder should be applied immediately. No more than a dozen or so sheets should be printed ahead of the bronzing. Carry merely enough size on the press to cause the type-form or plate to print clearly. An extra-heavy flow of color will retard drying and will cause a wastage of the bronze powder.
Bronzing may be done in rich-gold, pale gold, silver, green, red, etc. Rich-gold bronze powder is the most used for box wrappers. Fancy labels for perfume bottles, face powder boxes, etc., are often bronzed in green or red in addition to gold and silver.
Special bronze size, of the one color, will do for all colors of bronze.
BURNISHING
When it is desirable to have a brilliant polish on bronzed subjects of box wrappers, burnishing is done as follows:
After the wrappers have been sized and bronzed, and after the printing is thoroughly dry, the rollers and disc (or cylinder) of the press are washed clean of the size. We refer to the same press which has handled the form for the bronzing in question. The rollers are then removed. About four extra sheets of news or book paper are placed in the tympan, again underneath the fuller board, so as to make a stronger impression. The same plate or form of type which has been used for the size remains on the press. The bronzed sheets are then run through the press for the second time, feeding them to close register. This second “inkless” printing causes the plate or type-form to polish the bronzed subject on the sheets.