Abstract
This research was performed in response to an experiment that found that there was a lack of density in highly pigmented inks. The study was conducted to see if adding either a matte varnish or a gloss varnish to print would increase the density, color gamut, and tonal reproduction of the print. A test target consisting of an IT8.7/3 basic target and solid CMYK patches was printed using the flexography on the Comco Captain In-line Flexo press. Once the press run was complete, the IT8 and solid ink targets were read with a spectrophotometer and profiles were created with the ProfileMaker software suite. The addition of a gloss varnish to print was found to increase the density by approximately .2 while increasing the color gamut was also increased a little as well. The addition of a matte varnish, however, did not have a verifiable impact on the density, although it drastically decreased the color gamut of the print. Printing a varnish increased the dot gain roughly 2-4%. This research shows that density and color gamut can be improved, especially with inks that are highly pigmented, through the use of a gloss varnish. Further research can be conducted to determine if the matte varnish results could be improved.

Introduction
For many printers, consistent color and good density of a printed image is something that is very hard to attain. On January 1, 2006, in American Printer magazine, Joseph Marin wrote, “Why is maintaining consistent color so difficult? At any given time, the press operator is contending with print variables such as ink density, dot gain, gray balance and print contrast. And that’s just the press.” Many procedures have been done to try and help improve density. The aim of this experiment was to prove that adding a varnish to a printed image on a substrate will increase the density. The idea for this experiment arose because, in an earlier experiment performed by other students, highly pigmented inks were used to increase the density of an image. When the expected results were not obtained, the ink manufacturers suggested that because the pigment is loaded so high, there is less room by volume for resins to provide gloss.

The reflective quality of a gloss surface enhances density and makes the image “pop”. Using a varnish adds gloss and thus could enhance density (Simms, 2006). Gloss is defined as the light that is reflected from the surface of a material, where the angle of incidence of the light is the same as the angle of the greater part of reflection. The gloss is a characteristic of the surface of the material (Kipphan, 2001).

Many people use varnish to make their product look glossy and shiny as well as adding to other attributes of the finished product. On March 9th, 2006, Printing World stated, “Varnish is one of the most versatile tools available to the printer, fulfilling a remarkable range of practical and creative roles in a relatively modest way. Although its contribution is sometimes unseen and unappreciated, varnish can make the difference between good and excellent print.” Through the results of this experiment, printers might be able to more effectively use highly pigmented inks or be able to increase the density/overall appearance of already used inks. The varnish that will be used will also be able to add to other attributes of a package as well as increasing density. Another way increasing density with varnishes could help in the industry is with a small, independent printer who is unable to improve density without increasing their technology. They, too, can add a varnish to improve the density and gloss of the printed material. If the gloss of an image increases with the addition of a varnish, then fewer vehicles will be needed in the ink, thus increasing the density of the print as more pigment could be added.

This procedure has potential to impact practices in industry. The main objective of this experiment was to measure density, but gloss, dot gain, and color gamut were also measured, as varnish could potentially have an effect on those. Because there is more than one type of varnish, resulting in different effects, a glossy and matte varnish was used in this experiment. After contacting an industry representative, the idea was further encouraged by Warren Simms from Water Ink Technologies. He guided the experiment in the determination of which variables to change and which ones would really have no effect if changed. He suggested that for simplicity, the experiment should stick to one printing method: flexography, and one substrate: coated paper. Mr. Simms also thought it was a good idea to keep adding different thicknesses of varnish to see if this changes the outcome of any variables. This was addressed in the experiment through the use of a banded anilox roll.

Research Questions: Will the density of an ink increase as the thickness of a varnish increases? Will the varnish have an impact on color gamut or gloss? Will there be any difference when a glossy vs. a matte varnish is used?

Research Hypothesis: The density of an ink will increase as the thickness of gloss varnish increases as well. In accordance with this, the color gamut will increase as well. Adding a matte varnish to a substrate will also increase gloss. The addition of a matte varnish to print will cause the density, color gamut, and tonal reproduction to increase as well, but not to the same extent as the glossy varnish.

Null Hypothesis: Adding either a glossy or matte varnish to a printed piece will have no affect on the color gamut, density, or gloss of the finished product.

Operational Definitions
Density—Refers to a compound number representing the ability of a transmissive material to block light or the ability of a reflective surface to absorb light. The more light absorbed the higher the density. It is a measure of mass per unit of volume. In the case of printing, a product is very dense if each dot (unit) is big/has a lot of ink (mass) (Kipphan, 2001).

Gloss—The light reflected from the surface, whereby the angle of incidence of the light is the same as the angle of the greater part of reflection (Kipphan, 2001).

Varnish—A translucent, hard, protective finish applied to the surface of wood or other materials. Varnish finishes are often, although not always, glossy. Varnish has little or no color and is transparent, as opposed to paint, which contains pigment and is generally opaque. The varnish that we will be using is basically ink with no pigment.

Tonal Value Increase (TVI)—TVI or dot gain is the difference between the printed dot and the input dot. Dot area is found by using the Murray-Davies formula and calculated from the remitted light intensity of solid and halftone areas (Kipphan, 2001)

Methodology
The first step to creating the test target design was to set up the design layout. An illustrator file was created that was the length of the repeat and width of the anilox cylinder, which was approximately 8.75” by 12”. Once the appropriate size was distinguished, the layout was divided into five separate lanes for each of the line screens on the banded anilox roll. When doing this, it is important to make sure the lanes on the layout are labeled the same as the lanes on the anilox roll. The anilox cylinder that was used in this experiment was banded 600, 700, 800, 900 and 1200 lines per inch. Each target lane was formatted to fit within the band size of 1.75” by 12”. Next, an IT8.7/3 basic target was inserted in each of the lanes. In the remaining space, solid (100 percent) square blocks of each process color (CMYK) were inserted for density evaluation. To calculate the dot gain, the 50% tonal scales were located in the IT8.7/3 target. Finally, the varnish plate was made to extend 1/8 of an inch over the edges of the CMYK targets to ensure a proper fit. Once that was complete, the flexo digital plates were ready to be imaged and processed. Using the direct-to-plate DuPont imaging processor, the plates were processed; DuPont digital thermal plates were used. Standard procedures for this equipment were used when processing the plates. Four plates were made for each of the four process colors and then a separate plate for the varnish. The varnish plate covered the entire image area printed in CMYK. When mounting the plates, we used 3M 1115 process printing sticky back.

After the plates were made, the Comco Captain In-line Flexo press was set up for the run. Each process color had the same anilox roll screening of 800/2.0. Water-based flexographic inks were used for each varnish and process color. For the process colors cyan and magenta, Performa SP 4C inks were used; however, for the process colors yellow and black Ultra-Plus Pro-Set inks were used. Water Ink Technologies provided both the matte and glossy varnish types. Next, the pH and Viscosity of each process color and varnish were measured. The pH should be between 9-9.5 and viscosity should vary somewhere between 20-25 seconds. When the pH was measured, the device was calibrated, and the meter was put in a buffer solution, adjusted accordingly and the pH was read (Table 1). For the viscosity readings, a #3 zahn cup was used and timed with a stopwatch until a significant break in the ink was seen. Water was added to the inks that were too viscous.

Table 1: Ink Characteristic

After this, each of the four ink stations were set up and the gloss varnish was placed in the fifth press station first. The last step before beginning the press run was to load the white-coated substrate through the press.

The press was started and first was run without engaging the varnish station. Staring off, the press was run at 150 fpm, however, due to some problems, the speed was reduced to 50 fpm for the continuation of the press run. After a good print had been established with proper registration and optimal color representation, the roll was marked as a reminder of where the good quality test sheets began. After this, the unvarnished stock was run through at a speed of 50 fpm for approximately two minutes. Once this had been achieved the roll was marked again of substrate to signify the end of the unvarnished test sheets and the beginning of the gloss varnish set-up. The water-based gloss varnish station was engaged and registered, the roll was marked again, and the press continued to run at the same speed of 50 feet per minute for two minutes. After completing this, the roll was marked once again to ensure the end of the gloss varnish and the beginning of the matte varnish set-up. The varnish in the fifth press station was changed from gloss to matte varnish; however, the impression was not adjusted. Finally, at 50 feet per minute the stock was run through the matte varnish for approximately two minutes.

In order for the experiment to have statistical significance, a sample size was calculated based on the variance, with a confidence interval of 95 percent, and an instrument error of +/- .02. To determine the sample size, the density was measured on thirty uncoated samples. This was first done with a D19-C densitometer with a polarized lens. Upon getting somewhat unusual results, the cyan densities were re-measured with a D19-C densitometer with an unpolarized lens. The density readings are displayed in Table 2. In Excel, the variance was calculated and is included in the bottom of the table. Once the variance was calculated, the highest variance (.00053) was placed into the following formula for sample size: Sample Size = t2∝ * variance/bound2. Based on the equipment used, the bound factor was +/- .02, and t2∝/2 = .05 ≈ 4. Based on this formula, the sample size was calculated to be 5.3. This number was rounded down to a sample size of five.

Table 2: Density Readings/Variance Uncoated Middle Lane

After the press run, the data was analyzed by separating the three test targets of unvarnished, gloss and matte substrates from the roll. Then, a chart was made for all of the results in an Excel spreadsheet. Different characteristics among the substrate types were conducted with a variety of separate tests. Density was tested using a D19C-unpolarized spectrophotometer to measure the density. For optimum results, the spectrophotometer was calibrated according to the programs instruction. Next, each of the CMYK 100 percent blocks for five sheets of the three tests were measured in a standard lit condition and recorded the results in an Excel spreadsheet.

For the gloss test, the test sheets were sent off to Water Ink Technologies, Inc. where they measured three sheets of each test with a gloss-meter on a 60° angle. To test the color gamut, the basic IT8 sample for this test was used. ANSI Committee Digital Data Exchange Standards established IT8 targets to help regulate the reproduction of color. The subset target we used was an IT8.7/3 target. The needed IT8 targets were cut out and taped aside each other for each of the five test sheets and measured them using a calibrated spectrophotometer. A spectrophotometer is used to measure spectral data, which is the amount of light energy reflected from an object at several intervals along the visible spectrum. These measurements resulted in a complex data set of reflectance values that are then visually interpreted in the form of a spectral curve. This data was recorded into another Excel spreadsheet. In MeasureTool, the data was compared to other like data to ensure that no oddities existed. Once the data’s validity was confirmed, each of the five spectral readings was averaged into one file, and a profile was formed through the program ProfileMaker. Once each of the profiles was made, they were compared to each other in ProfileEditor, and screen captures were taken of select graphs.

Another type of test we conducted was the tonal reproduction test that basically measures dot gain. After calibrating the D19C-unpolarized densitometer to the paper white and a 100 percent value of a black swatch, the 50 percent square was measured for one test sheet because there no extraordinary results were expected and the data was then recorded the results into the data spreadsheet. This is used to find the print contrast (or dot gain), which is defined as the total gradation between highlights, middle tones, and shadows in an original or reproduction.

Throughout the experiment, many things did not go as planned. The magenta unit of the press was producing banding that could not be corrected. While printing the matte varnish, buildup occurred on the 600 line-screen lane, which caused the test strips to adhere slightly together. Also, the press could not be run at the intended speed due to registration and maintenance issues. The gloss varnish plate break was located in the first bar of the IT8 target. The matte varnish did not have an even coating on some of the test sheets. Lastly, the densities were read in an un-evenly light location. Nonetheless, the information gained from the testing of the testing is able to be applied to situations outside of a test environment.

Results
Density: Adding a gloss or matte varnish did have an effect on the density of a printed color; however the matte varnish had somewhat unexpected results. As demonstrated in Figure 6, the gloss varnish had consistently higher values on all the different line screens. Matte varnish, however, generally had a lower value. These density readings can be found below in Table 3.

Table 3: Density Values – Final

As the amount of gloss varnish increased, the density readings increased as well. With the gloss varnish, the cyan ink increased the most with an increase of .21 points, while yellow was the least, as it stayed constant. The matte varnish produced opposite results. Outside of a few outliers, as the amount of matte varnish increased the trend indicates that an increase level of varnish actually decreases the density readings. The results obtained from this test were expected for the gloss varnish, however, unexpected for the matte varnish.

Color Gamut: Adding a varnish to a printed piece also appears to have a slight impact on the color gamut. The addition of a gloss varnish, as shown in Figure 3, increases the color gamut a small amount in only one area of the color space. However, the addition of a matte varnish causes a decrease to this area (Figure 4). A similar trend as with the density, a thicker layer of matte varnish has an inverse relationship with the color gamut. As matte varnish is increased, the color gamut becomes smaller (Figure 4.5 compared to 4.1).

Figure 3: 3D Color Gamut - Gloss Varnish/Uncoated
Gloss Varnish- Gray Represents Uncoated

Figure 4: 3D Color Gamut - Matte Varnish/Uncoated
Matte Varnish- Gray Represents Uncoated

As the lightness values increase, the color gamut of both the matte and gloss varnish begins to look much more like that of the uncoated (Figure 5.2); however, in the lower lightness ranges, the gloss varnish exceeds that of the uncoated, while the uncoated exceeds that of the matte (Figure 5.1). As a thicker layer of gloss varnish is added, the color gamut of the gloss vanish continues to exceed that of the uncoated at lower lightness values (Figure 2.1). As the lightness increases, the color gamut for all amounts of varnish begins to appear more similar to the uncoated. The matte varnish, once again, acts in the opposite direction but still varies greatly at lower lightness levels and becomes more similar to the uncoated at higher lightness levels (Figure 2.4 – Figure 2.6).

Figure 5: Comparison - Matte/Gloss 600 Line Screen
Gloss Varnish: Blue
Matte Varnish: Pink
Uncoated: Gray

Figure 2: Gloss Varnish - All Line Screens
Gray Line Represents Uncoated

Figure 6: Density Readings

Figure 7: Dot Gain

Dot Gain - Matte Varnish

Tone Reproduction: The addition of either a gloss or a matte varnish did have a small impact on the dot gain of a printed piece. As a varnish was added, approximately 1 to 3% increase was seen in the magenta, yellow, and black process colors, with the gloss varnish showing the highest increase. The addition of the gloss varnish did show the most increase in dot gain, which could help to explain the increase in density when a gloss varnish is added. Adding a thicker amount of varnish, however, did not have much of an affect on the dot gain of a printed item.

Gloss: The gloss of a surface is described by the nature of its ability to reflect light. The measurement is based on the different angles that light scatters in accordance with the structure of the surface. Glossmeters measure reflected light in only a few selected directions (Kipphan, 2001). The results of this test, read on a 60° angle, are as follows:

Uncoated: 29.6
Gloss Coated: 65.5
Matte Coated: 18.2.

Analysis
As predicted in the hypothesis, the addition of a gloss varnish to a printed piece did indeed cause the printed material’s density to increase, as well as produce a small increase in the color gamut. Printing a matte varnish, however, often decreased the density of the print. The results for the matte varnish varied a lot from what was expected. The prediction in the hypothesis was that the matte varnish would increase the density and color gamut of the print as well.

From the results gathered, it was determined that the addition of a gloss varnish to print caused the density to increase by .2, and also increased the color gamut a small percentage. As the amount of gloss varnish increased, the density readings increased as well. This is due to the fact that density is a measurement of light reflectance and the reflective quality of a gloss varnish enhances the density. The matte varnish produced opposite results from the gloss varnish. As the amount of matte varnish increased the density readings decreased. In terms of the effect that matte varnish had on color gamut, as the amount of varnish is increased the color gamut became smaller. A matte varnish does not have the same reflectance quality of a gloss varnish and is therefore limiting the amount of light it reflects causing the density reading to decrease.

The gloss results of each of the test sheets sums up the rest of the data quite nicely. The gloss of matte-coated paper is significantly less than that of the gloss-coated, and the matte is even less than the uncoated. These results explain why the matte-coated paper had a lack of density and color gamut, as the addition of a matte varnish actually took away gloss from the paper.

The amount of varnish applied seemed to have very little effect on dot gain, while the addition of either a matte or a gloss varnish increased the dot gain percentage. For the gloss, this could be due to the increase in density, but it is uncertain as to why the addition of a matte varnish, which actually decreases the density overall, increased the dot gain. The findings from the dot gain readings could also vary due to the fact that only one test strip was measured.

The research hypothesis is accepted with the gloss varnish; however, with the matte varnish it is rejected, and a modified null hypothesis would be accepted.

Conclusions
By adding to the overall appearance of a printed piece, gloss is able to increase the attention paid to the product (Kipphan, 2001). The gloss of the ink causes the image to pop; however, when working with highly pigmented inks this is often hard to achieve due to the fact that the pigment concentration in highly pigmented inks is very high, thus the ink has less room by volume for resins and other material to provide gloss. The gloss of an image printed with highly pigmented inks could be restored and density could be added through the use of gloss varnish. This addition would add even more appeal to an item printed with such high quality inks.

The purpose of this experiment was to test the effects that a varnish had on the density, color gamut, and tonal reproduction of a printed piece. Further research could be conducted to confirm if the matte varnish results are indeed accurate, and if so, is there anything that can be done to improve the results in any way. It would also be interesting to research possible uses of printing a gloss varnish over highly pigmented inks and what implications this could have for the industry.

Acknowledgements
Water Ink Technologies, Inc. provided the gloss and matte varnish used in this experiment; this company also conducted the gloss testing with the use of a gloss meter. Dr. Liam O’Hara also provided much help and guidance throughout the organizing, printing, gathering of data, and analysis of this experiment. Much appreciation is given to all who contributed to this experiment.

References Cited
Joseph M. “Match” American Printer. January 1, 2006. Lexis Nexis ™ Academic.

Kipphan, H. (2001). Handbook of Print Media. Germany: Springer-Verlag Berlin Heidelberg. p. 110-111.

“Paper Handling: Make the most of a versatile varnishing act” Printing World. March 9, 2006. Lexis Nexis™ Academic.

(W. Simms, personal interview, October 25, 2006)

Copyright 2008 Salmon Creek Publishing