Inks can be mixed to obtain a wide variety of colors to suit various purposes in printed materials.
Mixing Ink Without a Formula
If the color isn’t a critical element, the printer can easily obtain a pleasant color by mixing white or black with a few base colors to obtain many shades and tints of those basic colors.
A paragraph from Thomas MacKellar’s 1885 book, The American Printer, gives a very down-to-earth description of some basic color relationships which, if kept in memory, can be a guide to mixing color to obtain desired intermediate colors.
“A printer who has on hand a stock of yellow, carmine, blue and black inks, may produce other colors and shades by intermixing as follows:–
Yellow and carmine, mixed, will give …………… Vermillion
Carmine and Blue ……………………………….. Purple
Blue and Black……………………………………. Deep Blue
Carmine, Yellow and Black ……………………… Brown
Yellow and Blue ………………………………….. Green
Yellow and Black ………………………………… Bronze Green
Yellow, Blue and Black …………………………… Deep Green.
Lighter shades may be obtained by adding proper proportions of white ink.”1
Mixing Ink With a Formula
Over the years there have been many systems used to classify color and assist printers and artists with mixing colors to obtain particular results for “color critical” applications. The most popular system in use today is a specifying system called the Pantone Matching System® (PMS®). This system uses a basic set of 15 base colors, including black and white, to use in mixing 1,667 specific colors. The printed guide can be used by designers and customers in specifying what color they wish to use, and the printer’s guide has the formulas to use to mix the colors of ink to get the specified color. The pantone® formula guides are available from Pantone® directly or from major ink suppliers.
Here’s a typical ink mixing scenario:
A client wishes a heading printed in a brown color. They choose Pantone® #4625 as the color to reproduce. In order to obtain that color, the following formula is specified in the PMS® Color Formula Guide:
9 pts. PANTONE Yellow
7 pts. PANTONE Warm Red
6 pts. PANTONE Black.
The printer mixes the three colors to obtain one ink which should reproduce that color swatch when printed.
In reality, the ink proportions were developed with lithographic printing in mind, which generally lays down a thinner ink film than letterpress, so many letterpress printers add a percentage of transparent white to the formula in order to reduce the proportion of pigment so as to lighten the ink as though it were actually a thinner printed layer.
What about CMYK?
Another method of specifying color is by a specified percentage of four basic “process colors”, Cyan, Magenta, Yellow and Black. These colors are used in production printing of most commercial magazines, newspapers and brochures. These four colors, along with occasionally Orange and Green, when screened down appropriately with halftone screens, allow printing color images which, when printed together give the appearance of full color in illustrations and typographic matter.
These same inks can be used in the same manner with letterpress printing to get the same effect of color, but the process takes very precise printing of the four color plates in exact register, something which is possible with most presses, but takes an inordinate amount of skill and care. Most applications for letterpress printing do not require reproduction of process color illustrations, the printing of “spot color” from a single color plate with mixed color ink is the norm for the modern letterpress printer.
Basic Ink Mixing Technique
It is good to have a space set aside for ink mixing. A table with a steel, stone or glass top is ideal, but a piece of plate glass or metal on top of another surface will work well, too. The area must be relatively dust free and easily cleaned. Many printers use a piece of plate glass on top of a white cardstock so that the color of the ink can be evaluated during mixing. Good lighting in the area also assists with color evaluation. Commercial shops use lights as close to 5000K (the color of sunlight) as possible. In reality, just having a good mix of fluorescent and incandescent light in the mixing area is a good idea.
The Windowpane Press has a practice of mixing inks either on a sheet of acetate or coated paper to save time on clean up. To save any leftover ink, make a sandwich by placing another sheet of acetate on top. That way, you can see the color saved and the ink can be easily scraped from either inside surface of the sandwich which cuts down further on waste.
A few clean ink knives and or spatulas and containers for the mixed ink are essential. Ink mixing itself does not require inordinate ventilation, but cleanup of the mixing surface and tools does require good ventilation. A small scale or balance will assist with getting the proper proportions of each color to be mixed. The formulas are meant to be used by weight, but some printers get by by estimating the proportions by dabs, spoonfuls, extruded lengths (from tubes), etc. A simple balance or electronic scale can be obtained relatively inexpensively, and provides the security of using proper procedure when color becomes critical.
When working from a formula, the order of the inks is not critical. Many printers start with the lightest colors and add the darker slowly, checking the color as they go as the darker colors can quickly overpower the lighter ones, particularly if the formula has not been tested before for letterpress.
Whenever possible, skim the ink from the top of the can without digging into the can or disturbing the surface of the ink too much. Sometimes, the ink is too stiff to do this, or the ink may have a skin on it. In which case, lift up the skin to get the “good” ink, then place the skin back down so the ink is not exposed to air.
Transparent White & Opaque White
It is somewhat confusing to newcomers to the ink mixing process to run into the two types of white utilized in mixing inks.
Transparent white is an ink which has no pigment, but simply the other two elements of an ink, vehicle and dryer/modifiers. This ink is mixed with other inks in order to lessen the pigment load of the ink in order to either make the ink lighter or to make the ink more transparent. In general, transparent white has a lower viscosity (more “runny”) than pigmented inks, and can also be used in limited situations to thin an ink which is too thick to roll out to an even tone.
Opaque White is an ink which has a fairly heavy load of white pigment. These days titanium white is generally used in white inks. These inks are sometimes called “cover white” as they can be used to create images on cover paper which may have a darker shade than text pages. This ink can be used in mixing, but generally serves the purpose of lightening the ink with which it is mixed. It is used in creating tints of colors and pastels.
- 1. MacKellar, Thomas, The American Printer, Mackellar, Smiths & Jordan Company, Philadelphia: 1885.↩