Printing with Halftones – 3 Part Series

Most printers are familiar with 4 color process halftone printing with Cyan, Magenta, Yellow and Black transparent ink. However, there are several ways to print halftones. Which way you choose to create your halftone separations will depend on your knowledge of these processes, what software and film printer you use to output your films and the look you are going for with your artwork on your garment. The next 3 months I’ll explain the Pros and Cons each process.

This month I will discuss 4 color process, AM (Amplitude Modulation) separations and printing.  Next month subject will be Flamenco simulated process. And in April, the subject will be Stochastic, FM (Frequency Modulation) process. Master these 3 processes and you will be able to print any design. Let’s get started.

Halftone is the reprographic technique that simulates continuous tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient like effect. Halftoning is commonly used for printing color photo realistic pictures. However, you can create really cool halftone designs using just one color. It looks best if the design has a lot of detail and contrast. Other factors that affect your halftone is dpi (dots per inch) resolution, lpi (lines per inch) frequency, angle and dot shape (round, square or elliptical). I’ve discussed those in earlier blogs.

4 Color Process, AM Screening 

The most common method of creating screens, amplitude modulation, produces a regular grid of dots that vary in size. Printing is made possible by repeating the halftone process for each subtractive color, CMYK, each at a different angle. The transparent property of the ink allows halftone dots of different colors to create full color effect. Best case scenario is your printing creates a nice pattern called a Rosette. Each of the four colors is printed in a grid of dots. So that the dots are not overlaid exactly on top of each other, the grid for each plate is turned at a different angle. When printed together, they form a rosette pattern. Worst case scenario is your printing creates a moire pattern. The happens when your lpi, angle and dot shape doesn’t work on the fabric you are printing and creates a wave or banding pattern.

PROS

Can create full color designs using only 4 colors.

Printing has a soft hand feel on the fabric.

Ink usage is lower than other processes.

Ink color inventory is less.

Less varying number of screen meshes necessary.

CONS

Because of transparency, printing is best on light colors.

Lighter vibrancy than opaque spot colors.

Each squeegee strokes needs to be consistent or variations occur.

Custom color match can be difficult.

Fabric can affect printing creating moire patterns.

Screens must always be very taunt.

Screen prep is more critical than other processes.

Registration is more critical than other processes.

Shirt broads must be clean and smooth as to not affect print.

Prints best on smooth fabric.

Testing and practice are necessary. Don’t be afraid to do both. You can print on color/dark fabrics using a backer. However it is very sensitive and tricky to master. That’s where a great artist, testing and practice really come in.

Until next month , when we will discuss Flemenco simulated process printing using opaque spot colors and halftones.

Cora Kromer
cora@qdigitizing.com