ELEMENT 3 - Adopt Thinner Ink Film Printing

Thinner films of wet ink are easier to control, print sharper graphics and increase your graphic reproduction ability. Reduced ink film leads to less dot gain and improved print contrast.

A banded anilox roll test determines what volume of ink supplied to the plate will produce the optimum print density, dot gain and contrast. This is a special anilox roll with sections (bands) at different line screens and volumes. Using a plate with appropriate combinations of solids, reverses and tints, and a densitometer to quantitatively measure results, you can determine the thinnest ink film thickness to give the best performance for each printing application.

The graph above shows densities of black ink from an actual banded roll test. These densities correlate directly with the ink film thickness being applied. From this analysis, ink film thickness targets are determined against densities or Spectrophotometer values needed to achieve the desired colors. These are the quality results that Harper guarantees.

There is an alternative to the banded roll test that can benchmark your color. Though it takes longer, we can still systematically correlate results as rolls are purchased. First, we will benchmark a roll and the color it delivers. Then we will compare the results to a second roll (using the same ink, color, and viscosity). The final comparison is your color curve performance. Though not as scientific as banded anilox testing, it is still very effective if designed and controlled properly.

ELEMENT 4:  "Snapshot" Provides Key Information

The SHARPER System "Snapshot" is a special target image printed on each press under controlled conditions to provide key information between the flexo printer and the prepress tradehouse. The Snapshot target was specially created through the joint efforts of prepress, printing and anilox roll experts. Precise measurements allow adjustments for dot gain, gray balance and other critical factors to be made in electronic prepress and plate production stages, specifically tailored to your printing system. The SHARPER System Snapshot tests overall control of 4-color process printing as well as characterizing general print accuracy. Its components are as follows:

Target Image Descriptions

Plate Mounting Aids
Cross marks define a line parallel to the image center and plate cylinder, for optical mounting systems. Microdots are included as shown. Plates may also be drilled for pin mounting.

Registration Marks
Registration marks are included to check for film and press registration. In addition to the conventional film registration mark with color indication, there is a railroad track version. The railroad track version is especially useful for judging registration accuracy on presses equipped with video monitoring equipment. It also allows for measurement of register variation with a measuring microscope. These marks are designed for a register tolerance of +/-  0.004 inches.

Thick and Thin Rules
Thick and thin rules in positive and reverse are included in both the press and cross web directions. These lines are used to allow the designer to specify rule widths based on how they will apear when printed rather than as they may appear on screen. Lines in one directionp may appear differently than lines in the other.

The positive and reverse lines are broken in the centers to observe the effects of gain. Ideally, the lines should appear of similar width when printed correctly.

Many times, designers may include hairlines in a design which will totally close up with press gain. This target is intended to prevent this occurrence.

The lines in the digital target file are the following weights, starting from the center in points: 0.25, 0.50, 1.0, 1.5, 2.5, 3.5, 5.5.  A microscope with measuring capability can be used to provide a measurement of line image gain.

Positive and Reverse Type
The image in the digital target file includes positive and reverse type in both serif and sans serif styles in 4, 6, and 8 point sizes. These elements are used to define the minimum positive and reverse type sizes which can be satisfactorily printed on your press. They also allow a designer to visualize the effect of size and weight on appearance and legibility.

Use caution. These elements define the appearance of type combined with your process images. Much more gain is anticipated under conventional line work or solid printing set-ups.

Slur & Impression Hexagon
These gauges are used to precisely set impressions for anilox and plate. Paralleling of these settings is accomplished by comparing the targets on the left and right edges of the web.

At optimum anilox and print impression settings, the target should appear in a uniform color. If this result cannot be achieved, a slur condition (speed differential between substrate and plate surfaces) is indicated.

The targets are composed of parallel microlines. Their uneven growth in different segments will create lighter and darker visual effects to indicate improper settings.

Grey Scales
Non-overprinting grey scales are provided for four colors. The file input dot area percentages are shown in the template. Scales run in darkening and lightening sequence to encourage balance on the press set-up and an average for color separation dot gain curves. Normally, the gain curve data is obtained by reading and averaging the density information from the two center columns. The points in between can be added for research purposes.

Grey Balance Targets
Grey balance analysis targets are used to determine the relative densities of cyan, magenta and yellow required to produce a neutral grey. Neutral grey is defined as reflecting equal portions of red, green and blue light.

The targets are constructed to have a proofing system neutral in the center. The same value of cyan is present in all hexagons within a given block. Magenta values
decrease from top to bottom and yellow values decrease from right to left. The background of each block contains a black screen to aid with visual comparisons. This large target can be evaluated with a densitometer.

Blocks are provided from highlight to shadow. The cyan values for these blocks (reading left to right and top to bottom) are 5%, 10%, 15%, 20%, 25%, 30%, 40%,
50%, 60%, 70%, 80%, 85%, 90% and 95%. Also included is a grey balance strip target that includes hexagons with the same values as the center value of each block. These may be measured with a spectrophotometer to provide grey balance information as variance from the proofing system.

UPC Symbols
UPC Symbols are included in both the machine and cross machine directions to determine optimum bar width reduction for symbols printed with the process color roll being characterized.

Large Solid Overprints
The large solid overprints allow viewing of ink film integrity issues. Issues such as mottle, pinholing, and adhesion can be identified.  The overprinting areas allow for a visual examination of ink trapping issues.

Vignettes
A vignette of each color is included to allow for visual examination of issues including banding, bridging, speckle and highlight drop-off.  It can assist in differentiating between an ink drying too fast or inadequate resolubility.

Gretag® CMYK Image
This image provides overprint and trapping information allowing the user to obtain spectral data with a spectrophotometer. This information provides increased accuracy in obtaining desired overprint colors.