Introduction

In this project, we are testing the differences that result from printing in varied layering sequences of subtractive primaries.   We are using the technique of silk screening, or serigraphy, to produce these prints.   Once we have created an original design and the means by which to print it multiple times, we will test the gradations of color in the resulting prints using a colorimeter (L* a* b* coordinates).

Background

Silkscreen printing has been a form of reproducing images since between 500 and 1000 A.D. The Japanese first began with a more rudimentary process that used a stencil without the screen. This allowed for bold prints, however the prints lacked the finer details. They began to construct a webbing using fine silk threads and human hair to weave a netting that would support the stenciled images. This allowed for delicate and intricate designs to be produced with almost limitless complexity. The process was later brought to western culture by explorers such as Marco Polo in the early 14th century. The silkscreen process became popular in France in the late 19th century when it was used for printing on textiles. The printing itself involved a silkscreen and a stiff bristled brush. Later the squeegee was introduced, making commercial and automatic printing a possibility. In the 1920's a printmaker, Louis D'Autremont, developed a knife-cut shellac stencil material called Profilm. This would later be improved by Joseph Ulano, who introduced a lacquer material as well as a photosensitive material, more akin to the printing techniques used in our experiment. The silkscreen technique became widely popular for commercial use in the mid- to late 20th century. Later the process would become an avant-garde form of art known as Pop Art. Artists such as Andy Warhol, Jasper Johns, or Roy Lichtenstein employed the silkscreen process to further the meaning behind their art, and as a commentary on commercialism and society at the time. The method transferred easily to the flat colors and precise edges of Minimal Art and also was useful in the growing trend of photo realistic art. The silkscreen process was also particularly popular because it was more cost effective as well as easier to operate than various other printing techniques.

Procedure

Materials:

• 4 Wooden Frames
• Polyester monofilament screen fabric
• Duct tape
• Staple gun/staples
• Photo emulsion (Ulano Fotocoat TZ)
• Emulsion coater tray
• Transparencies
• Timer
• Squeegee
• Spatula
• Watch glass
• Liquid screen filler
• 100% cotton white t-shirts
• Paper
• Speedball water based fabric screen printing ink
• Cyan
• Magenta
• Yellow
• Black
• Clear extender base

For the Design:

1. Determine and sketch an initial design.
2. Using Photoshop, try to recreate design as accurately as possible.
3. Separate the layers of color, making sure to utilize the CYMK color scale.
4. Print each layer onto a separate transparency (using black ink as the negative).

For the Screens:

1. Using wooden frames and polyester monofilament screening material, stretch the screens (making 4 in all for our design).   Pull the screen fabric taut over the frame and staple the edges tightly.   Line the outside of the screen with duct tape to keep paint from spreading during the actual printing process.
2. Coat the screens with photo emulsion one at a time in the darkroom, making sure not to expose them to any UV light during the process.
3. Spread a thin, even layer of photo emulsion over the screens covering enough space to ensure that the image will have sufficient room to be transferred from the transparency to the screen.
4. Set in separate boxes and allow to dry in darkroom overnight.

For the Shooting of Images: (NOTE:   The lights should be off at all times during this process, as the screens are still extremely light sensitive and the images will not transfer if they are exposed prematurely.)

1. Tape a single transparency to the dried screen (applying to the side that has been treated with photo emulsion).
2. Make sure the image looks right-side-up when laid down on the light box.   (This is a "photo" image transfer, meaning it should produce directly and not a mirror image).
3. After laying the screen on the light box surface, place the felt and cardboard (both cut to size) on top of the screen making sure to cover the image completely.
4. Apply excess pressure using an evenly-weighted object.   (we used piles of magazines for this step).
5. Place a large black felt to cover the entire light box and screen.   This ensures the maximum exposure.
6. Set timer.
7. Turn on the light box, trying for 2 minutes initially, observing the results and altering each one after that accordingly.
8. After the time is up, remove the layers. (KEEP THE LIGHTS OFF until the screen in completely rinsed).
9. Take to the sink immediately and remove the transparency.
10. Rinse the screen well, applying gentle pressure to it to remove excess photo emulsion.   Focus especially on the area where the image should be; try to clear the screen enough to see the design clearly through it.
11. The screen will no longer be light-sensitive, so remove from the darkroom and let it dry.  

For Printing:

1. Create a template for the prints so that you can align the paper with the design each time.
2. Label screens with the color ink that you will be using.   Make sure to figure out which way the screens need to lie in order to print the image desired.  
3. Put a line of ink just above the stenciled image.  
4. Using a squeegee, pull the ink down over the image trying to keep it even and in one fluid motion.   (Repeat if necessary for optimal coverage and print results).
5. Clean the ink promptly from the screen.   It is water soluble but difficult to remove if left to dry.
6. Allow to dry and repeat with the different layers of colors/inks as desired.   (The drying process can take anywhere from 1 to 12 hours, depending on the ink, the thickness of it, and the medium to which it is applied).

Observations and Data

When we were working with the screens in the darkroom for the first time, we noticed that the photo emulsion is relatively tricky to work with because it really must be a large even area that is coated and you must move quickly when working with it. For our design, this was not as big of an issue because we were able to work around the areas of buildup on the screen with our small images, but if you are printing a large image on one screen, you must create a wide even surface with which to work. When we exposed the screens and transparencies to the light box, we experimented with different exposure times to see which ones produced the best results. For the first one, we set the exposure time at 2 minutes; for the second, 1 minute, 45 seconds; for the third, 1 minute, 30 seconds; and for the last one, 1 minute, 35 seconds. We found that the third screen came out the best, so 1:35 was a good exposure time for the given circumstances.

The actual printing process was not very difficult as long as the images were lined up straight with the template and the screen did not shift. Our prints came out clear for the most part and demonstrated our point --that the sequencing of layers affected the resulting colors-- well. Most of the screens held up very well throughout our experiment, but the one with the black image (the writing, the title and the painter's palate) loosened up a little after a few uses, causing slight leakage of ink onto the other side of the screen. We were able to remedy this with small pieces of tape on the reverse side which did not allow ink to pass through for the most part. If this is an issue, you can use freezer paper or duct tape and create a "frame" around the image to be printed so that the ink is contained within a given space and does not leak out elsewhere.

When printing the images, we observed that going in a certain direction can greatly affect the outcome. For example, when working with the black ink and the title image, we needed to start from one side in particular, rather than the other, because the ink would not cover as well and would build up in the beginning part of the image if not. This is just something that we realized after a few prints and had to experiment with each different one; it may be different for every printing attempt.

We found that the inks really produce the best results when used on fabric (we used 100% cotton t-shirts), and although they worked on paper, the resulting colors were darker and more opaque. So while they were still magenta, cyan, and yellow, they did not look it as clearly at first glance.

The remaining observations were shown through our colorimeter readings and the comparisons we made using those.

1.2.3.

4.5. 6.

These are the results of the colorimeter readings for the 6 sheets of paper prints (shown above):

After these tests on the paper prints, we tried testing the colorimeter levels on the t-shirt prints as well. These are the results:

*We mixed the inks with the clear extender base as an enhancement to our experiment. This was not in the original plan but the results were very interesting to compare.

Conclusions

After finishing our experiment, we concluded that the sequence in which we layered the colors really does affect the resulting colors. This was evident in the variations that we found in our colorimeter readings. So in this case, our hypothesis proved true and we were able to see the outcome of it in our prints. In our enhancement printing, we found that the use of the clear extender base in conjunction with the inks produced a slightly better print overall; also, by creating a more opaque image, it provided us with a clearer representation of the variations in subtractive primaries when overlapped. Our final experiment differed slightly from our original plan only in the sense that we did not end up printing on all t-shirts. Instead we printed the majority of our tests on paper and then as an enhancement, we produced the print on three t-shirts.

Links

History of Serigraphy - William Mitchell

Screen-printing: definitions and more

Color matters & science: A source on subtractive primary colors

L* a* b* Calculator

Other References

Blick Art Materials: Resources for Art Educators. USA: Dick Blick Company, 2004. (This is an art supply magazine that we used as a reference for the tools we used)

Sacilotto, Deli and Saff, Donald. History and Process of Printmaking. New York: Holt, Rinehart and Winston, 1978. 288-297.

Acknowledgements

We would like to thank Christi Teasley for helping us so much throughout the process. She showed us how to work with the materials needed and showed us in detail how to perform certain techniques. Without her assistance and the facilities available to us at St. Andrew's, we would not have been able to accomplish our goals in this project.