HINTS FOR PRESSMEN
COVER WHITE
When cover white is too short or stiff to be workable, add a small amount of mixing white.
PROCESS COLOR PRINTING
For the very best results in this fascinating art, print the lighter colors first, as follows: Yellow, red, blue and black unless otherwise instructed by the engraver.
When dark colors are run first contrary to progressive proof, the full richness and detail are lost and hues altered. Light colors printed over the dark detail, modify and subdue the sharpness which is not always desirable.
Use opaque yellow for the first color when printing on tinted stock; follow with transparent colors.
GOLD SIZE FOR BRONZE POWDER
All pigment that enters into the manufacture of gold size must be earthen. Yellow ocher is admirably adapted for this purpose, as in hue it ranges from a pale yellow to light brown. It is insoluble in oil and will not dull the luster of bronze powder or bleed through.
Gold size for pale gold bronze should be pale yellow; for deep rich gold bronze use medium light orange brown size.
Deep rich gold when applied over pale yellow size produces a medium gold cast.
STREAKING AND SHADOWS
Streaking or shadows which occur when running heavy solids, can oftimes be overcome on three roller platen presses by using a steel vibrator, also expansion trucks which trip third roller. If expansion trucks are not available use vibrator and remove third roller, as in most cases this roller is causing the trouble.
Coach varnish adds lustre to printers’ ink.
MOTTLING AND PICKING
Mottling of printers’ ink is largely due to an over-abundance of reducer, which separates the pigment from the mordant. This difficulty is sometimes overcome by adding silicate of soda (water glass), magnesia, etc. These absorb some of the superfluous oil and force the pigment into a solid mass.
Reducing to eliminate picking is the principal cause of mottle. Before mixing reducer with ink, add a little soft ink, such as halftone; if straight halftone picks, add 00 varnish.
Inks are made for all purposes. Best results are obtained by using them without adulteration. Oftentimes a drop or two of linseed oil distributed on press will do the trick. If ink mottles from the start with no other inks at hand, use less ink and double roll.
Picking and mottling on platen presses is more prevalent than on cylinders. The reasons are obvious. The cylinder requires less ink, has ample distribution and the printed sheet is peeled from the form.
Every printing press has its capacity. You can not successfully print a solid oversize form just because it can be locked in a platen chase. Even with a good vibrator, this kind of form requires double or triple rolling. Taking into consideration the fact that friskets jerk printed sheet from the form, you need not look farther for the cause of picking.
By cutting stock two or more up, and inking form the narrow way with enough of the sheet to be printed protruding for a good hand hold, you can peel it from the form. Do not allow friskets to touch the sheet.
WASH FOR DIRTY TYPE OR CUTS
Crude carbolic acid and turpentine, equal parts. Let stand over night. Rinse off with gasoline.
Color Printing—Some very pretty effects are obtained by printing transparent yellow and crimson or scarlet over black. The black being so modified as to yield greenish hues under yellow and purple hues under red.
GENERAL PURPOSE GLUE
Fill a quart glass jar with good broken glue; then fill up with acetic acid (which is vinegar in a strong form); set jar in hot water for a few hours to dissolve.
PADDING GLUE (any color) FOR PRINTERS
In addition to the above formula purchase ten cents’ worth of analine (any color desired) from your druggist, dissolve this in two ounces of glycerine. Then stir all together. The glycerine keeps the glue flexible and prevents cracking. This formula, in print for the first time, means the saving of a great many dollars.
MIXING GLASS
Before mixing colors on glass, glue or lay a sheet of white paper to the back. Or paint it white.
WHEN TO USE OPAQUE PROCESS INK
When printing process colors on tinted stock, use an opaque yellow, follow with transparent colors.
PROTECTIVE VARNISH FOR PRINTERS’ PLATES
Printing plates, especially etchings which are chiefly composed of zinc, may be kept free from corrosion by dipping or painting with a liquid solution of gum arabic, which is soluble in water.