| Tools for teaching - A visual aids workshop, and instruction manual for health educators |
|Session 7. Project $3: Design/project #4: Planning 7.0|
|Handout 7.7.1 - A silkscreen manual (Supplementary learning materials)|
Silkscreening is a printing process which uses a screen of silk or other fine-meshed fabric as a stencil. A squeegee is used to press ink through the fabric on to the paper or other material below. The image to be printed can be applied to the fabric screen in several different ways. This manual provides instructions for the cut stencil method.
1) Construct a frame from 1" x 2" lumber slightly larger than the largest poster you plan to make. (Suggested size: 24" x 36")
2) Make a baseboard from V plywood the same width but 2" longer than frame. Attach a 1" x 2" headboard securely at one end.
3) Attach frame to heading of baseboard with pin hinges so that frame can be easily removed for cleaning.
A squeegee is used to pull the ink across the silkscreen and force it through the open areas of the stencil onto the paper below. The squeegee should be approximately 2" shorter than the width of the screen. A screen 24" x 36" requires a 22" squeegee.
Squeegees may be purchased at a silkscreen supply store and are generally priced per inch. If you prefer, you can make your own squeegee by one of the two following methods.
Bolt a flat piece of rubber (4" wide x 22" long x ¼" thick) between two pieces of wood (3" wide x 22" long x ½" thick).
Wrap a piece of inner tube or thin rubber around a stiff 22" long strip of metal or thin plywood. Mount in a wooden frame which is also 22" long.
1) Remove pins from hinges (you'll probably need a screwdriver to do this) and separate frame from baseboard. Replace pins in baseboard hinges so they will not get lost and set baseboard aside. Place frame top (hinge-side) down on the work table.
2) Cut fabric about 4" longer and 4" wider than outer dimensions of frame. (For a 24" x 36" frame constructed from 1" x 2" lumber, you will need to cut the silk 32" x 44".)
3) Center fabric over frame allowing a 2" extension on all four sides.
4) Stretch fabric tightly over frame and staple securely to the outer edge of all four sides. Begin stapling in the center of each side, working outward to the corners of the frame, alternating from side to side. For best results, this operation should be done by two people: one to pull the fabric tautly across the frame and hold it in position; the second to staple. Staples should be placed no more than 1" apart.
5) Now, go back around the frame, turning under the raw edges of the fabric and securing them to the frame with a second row of staples. Fold and staple corners neatly. Add a third row of staples on the uppermost surface of the frame.
6) Seal the inside edges of the frame on both sides with gummed paper tape or masking tape. Be sure that the tape covers all the staples. Cover tape and inside edges of the screen with a light coat of lacquer.
7) Attach frame, screen side down, to heading of baseboard by reinserting pins into hinges. The frame is now ready to have stencils attached.
Art for silkscreening with a cut stencil should be designed with large, simple shapes and a minimum of copy lettered in a bold type face. All line work should be bold also for ease in cutting the stencil. Separate, rather than overlapped, components will make the printing process simpler.
1) Once the concept has been developed, draw a tight comp of the design to size. A tight comp (an abbreviation for "tight comprehensive layout") is art that looks exactly the way you want the printed piece to appear. The size, placement, and color of all components, including the type, must be accurate. The tight comp may be drawn on brown paper.
2) The next step in preparing artwork for silkscreen reproduction is to keyline the design.
• Tape the tight comp securely to your work table.
• Center a piece of tracing paper over the tight comp and tape the top edge to the table so that it will not shift while you are working.
• Using a fine point black pen, carefully outline each separate component and color area in your design. Use a ruler for straight lines. Lift the bottom edge of the tracing paper from time to time to check your tight comp against your keylined pattern. Be sure you are not missing any details.
3) Now you are ready to make your color separations following the keylined pattern.
• Remove the tight comp from under the keylined pattern. Set it to the side where you can refer to it as you work.
• Tape the other three sides of the keylined pattern to the work table.
• Place a clean piece of tracing paper over the keylined pattern and tape it down securely so that it will not shift.
• Using the tight comp as reference, carefully outline all the elements that are to be printed in a single color. Label this piece of tracing paper with the color it represents, e.g. red stencil.
• Remove the first color separation and place another clean piece of tracing paper over the keylined pattern. Outline all the elements to be printed in the second color and label the tracing paper accordingly.
• Proceed in this manner until all the colors have been "separated".
NOTE: It is possible to print more than one color from a single stencil provided that those color areas are separated from one another by sufficient space to allow you to effectively block out one color area while you print the other. This can be done by taping a piece of plastic or heavy tracing paper to the bottom of the screen over the color area that is not to be printed. In such a case, the color separation should indicate the outlines of the two colors that will be printed from the single stencil.
Blue film, the material from which silkscreen stencils are usually cut in the Philippines, isn't really blue at all, but grey. This translucent, lacquer-base film is supported by a light weight paper backing. When it is placed over the color separation on a light table or white background, the stencil cutter can easily see the keylines through the film.
The first-time stencil cutter needs to become familiar with the amount of pressure required to cut the film without going through the paper backing. Practice cutting on a small piece of film before tackling the actual stencil.
The steps in cutting a silkscreen stencil from blue film are as follows:
1) Tape color separation securely to work table. If the table is dark in color, place an opaque white backing between the table and the separation.
2) Cut a piece of blue film the size of the open area on your screen.
3) Center it, film side up, paper side down, over the color separation and tape securely to the table.
4) Using the point of an exacto knife with a #11 blade, carefully cut out each color area following the keylines on the color separation precisely.
REMEMBER: Don't press too hard. You want to avoid cutting through the paper backing. Be sure the entire outline has been cut cleanly and completely.
5) Use the edge of the knife blade to remove the film from those areas you want to print. This can be done by lifting an edge or corner of the film you want to remove just enough so that you can grab hold of the film with your fingers. Slowly peel the film away from the backing and discard.
6) After the stencil has been completely cut and all unwanted film peeled away, remove the tape and detach the blue film stencil from the table. Cover the stencil with the paper color separation and roll, film side in, to protect the image. Set the cut stencil aside until you are ready to adhere it to the screen.
7) Repeat this procedure with a fresh piece of blue film for each color separation.
NOTE: It is not always necessary to cut the stencil on blue film. Simple shapes can be cut from any waterproof material such as heavy plastic or exposed x-ray film and taped to the underside of the screen. You can even use heavy weight tracing paper provided you are not going to make too many copies. A gestescript or any other hand or typewritten stencil may also be used. With the possible exception of the x-ray film, none of these stencils can be reused.
Because blue film is a lacquer-base material, it is soluble in lacquer thinner. The secret to adhering the film to the silkscreen is in using just enough lacquer thinner to soften the film sufficiently so it will stick to the screen, yet not so much that the stencil dissolves altogether, destroying the image.
Blue film stencils, properly adhered to the screen, are reusable for multiple printings. Beginners should practice with a small piece of film in an empty corner of the screen.
Lacquer thinner will remove nail polish.
Wear rubber gloves to protect your manicure.
1) Set the silkscreen attached to its baseboard on the work table.
2) The stencil should be adhered to the bottom side of the screen. Lift the frame and position the stencil, film side up, on the baseboard. Some people find it easier to bond the stencil to the screen if there is a "cushion" of newspaper to work against. Try placing several layers of newsprint on the baseboard before positioning the stencil.
3) Now, lower the frame and adjust the stencil so that it appears in proper printing position on the screen.
4) Moisten a rag with lacquer thinner and, using firm pressure in small, circular motions, dampen the silk as you press it on to the stencil. Alternately press the dampened silk firmly on to the stencil with a dry cloth. Work on only a small area at a time, beginning in the center and slowly working outward until the complete screen has been dampened and pressed into the blue film. The whole stencil should adhere to the screen when the frame is lifted. Two or three persons can work at this task simultaneously.
5) Allow the screen to dry for a few minutes. Then, very gently, carefully, and slowly, peel the paper backing away from the bottom of the screen. If you should notice that the film is also pulling away from the screen, lower the frame again and use a little more lacquer thinner on the rag to readhere the stencil.
6) Once the stencil is adhered to the screen and the paper backing has been removed and discarded, check for any open areas between the outer edge of the stencil and the frame. Seal these with gloss varnish so that the ink will not be pushed through these spots when you print. You can also touch up the edges of the images, if necessary, with a small brush dipped in the gloss varnish. Clean the brush in lacquer thinner immediately after use.
7) Set the silkscreen aside with the frame propped open so that the silk will dry thoroughly. The silkscreen cannot be used for printing unless the stencil is properly adhered and the screen is completely dry to the touch. Allow at least 30 to 45 minutes drying time.
8) Repeat this procedure, adhering each of your stencils to a different screen.
1) The secret to successful silkscreen printing is in knowing the compatibilities/incompatibilities of stencils, inks, and solvents.
• The ink must not dissolve the stencil because the image will be destroyed.
• The stencil must have a solvent or the screen will be useless for further printings.
GUIDELINE FOR STENCIL/INK/SOLVENT COMBINATIONS
Water soluble stencil
Lacquer soluble stencil
limited # of copies
- - -
2) As noted in the above chart, there are two types of silkscreen ink: water-base ink and oil-base ink. Both types may be purchased commercially, however the most commonly used (and thus most widely available) commercial silkscreen ink in the Philippines is a water-base textile ink. This ink may be used on paper as well as textiles provided the paper stock is somewhat porous, i.e. has not been coated with a hard, slick finish. The type of inexpensive paper recommended for the visual aids workshop accepts this water-base textile ink without any problem.
3) If you prefer to make your own silkscreen ink, both oil-base and water-base inks may be homemade according to the following directions:
• RECIPE #1 (oil-base ink)
Thicken ordinary oil-base paint with wood-filler, talc, or powdered clay to a consistency halfway between heavy cream and pudding (or champarado without any lumps).
• RECIPE #2 (water-base ink)
non-instant starch 120 ml. (½ cup)
boiling water 350 ml. (1½ cups)
soap flakes 120 ml. (½ cup)
coloring (tempera paint powder, ink, or food coloring)
Mix starch with enough cold water to make a smooth paste. Add boiling water. Cool until glossy. Stir in soap flakes while mixture is still warm. After the mixture has cooled, add coloring.
• RECIPE #3 (water-base ink)
cornstarch 60 ml. (¼ cup)
boiling water 460 ml. (2 cups)
soap flakes 30 ml. (1/8 cup)
coloring (tempera paint powder, ink, or food coloring)
Dissolve cornstarch in a small amount of cold water.
Mix two or three tablespoons of boiling water, one spoonful at a time, into the cornstarch mixture.
Stir well to get rid of all the lumps. Pour the cornstarch mixture very slowly into remaining boiling water, stirring constantly. When mixture boils, reduce heat and continue to stir until thickened. Add soap flakes while still warm. Cool and add coloring.
• RECIPE #4 (water-base ink)
cornstarch 120 ml. (½ cup)
gelatin (unflavored) 1 envelope or 15 ml.
soap flakes 120 ml. (½ cup)
water 700 ml. (3 cups)
coloring (tempera paint powder, ink, or food coloring)
Dissolve cornstarch in 170 ml. (3/4 cup) cold water.
Dissolve gelatin in 60 ml (% cup) cold water. Bring 460 ml. (2 cups) of water to a boil. Stirring constantly, slowly pour in cornstarch mixture followed by dissolved gelatin. When mixture begins to boil again, reduce heat and continue to stir until thickened. Cool mixture, then add soap flakes and coloring.
NOTE: One or two teaspoons of glycerine added to the water-base inks will make them smoother and easier to use. All four of these homemade inks will last for several months if stored in jars with tight-fitting lids.
4) Standard black mimeograph ink may also be used to print handwritten or drawn gestescript stencils or typewritten stencils. Standard mimeograph ink is an oil-base ink, soluble in turpentine.
5) A word about color -
Bright, bold colors are most effective for. visual aids and display posters. Try to avoid pastels and muted shades. Buy or mix RED, YELLOW, BLUE, GREEN, and BLACK. From these five colors you can also make ORANGE (from RED and YELLOW), PURPLE (from RED and BLUE), and BROWN (from RED and GREEN, or PURPLE and YELLOW).
Silkscreen printing and clean-up can be very messy procedures. Be sure that you wear old clothes or a large apron, smock, or lab coat that completely covers your garments.
Plan to print the black stencil first. This will make registration of the rest of the colors much easier.
The first color run:
1) Cover work table with brown paper or old newspaper.
2) Place silkscreen bearing black stencil on table with hinged end facing away from you.
3) Assemble your materials - ink, masking tape, squeegee, rags, and one or two small pieces of stiff cardboard (these can be cut from an old carton) or a couple of tongue depressors.
4) Stir the ink well with a stick and thin, if necessary, with a small amount of water (water-base ink) or turpentine (oil-base ink). The consistency of the ink should approximate that of a smooth champarado, i.e. a thickness halfway between heavy cream and pudding.
5) Stack the paper on which you are going to print convenient to your work area but not so close to the screen and ink that it will get soiled.
6) Lift the silkscreen frame and position the first piece of paper on the screen baseboard.
7) Lower the frame, checking to make sure that the image is centered on the paper and that margins are equal. Adjust paper as necessary.
8) When paper is in position, raise screen and, without shifting the paper at all, place a cross of masking tape, 2 layers thick, flush with each of the two bottom corners of the paper.
These masking tape guides-will help you to position subsequent pieces of paper so that the image will be uniformly printed on all copies of your poster.
9) Now lower the frame once again and pool about ½ cup of ink across the end of the screen furthest from you.
10) Hold the squeegee firmly with both hands and set it perpendicular to the screen between the edge of the frame and the pooled ink. In one firm, even motion, pull the squeegee toward you, spreading the ink across the screen and forcing it through the open areas of the stencil onto the paper below.
11) Carefully set the squeegee aside. Lift the frame and remove the printed paper. Lay the print flat in an out-of-the-way spot where it can dry.
12) Place a clean sheet of paper on the screen baseboard, positioning it flush against the masking tape crosses. Lower the screen.
13) Walk around to the other side of the table and use the squeegee to pull the ink back across the screen. Set the squeegee aside, lift the frame and remove the second print as you did the first.
14) Continue in this manner, adding more ink as needed, until you have printed the desired number of copies.
NOTE: Plan on printing 8 to 10 more copies than you actually need. These extra copies will serve as "proofs" when you are trying to register the second and subsequent color runs. You are also bound to have one or two mishaps - a few extra copies are insurance that there will be sufficient "good" prints to fill your needs.
15) When you have finished printing the first color, use a small piece of cardboard or a tongue depressor to scrape the excess ink off the squeegee back into the ink container. Scrape up and save the excess ink left on the screen. Cover the ink container tightly and store for future use.
16) Clean screen and squeegee thoroughly (see SILKSCREEN CLEAN-UP).
• The second and subsequent color runs:
1) To print the second and subsequent color runs, set up your work space and materials as you did for the first color.
2) Be sure that prints are thoroughly dry before printing subsequent colors. Generally speaking, this should only take about thirty minutes for water-base inks.
3) Place the screen bearing the stencil for the next color you are going to print on the work table.
4) Lift frame and position one copy of the partially printed poster on the baseboard. Lower screen and adjust paper so that the area to be printed is in the proper relation to the previously printed color. This is called color registration. Use the tight comp (from SILKSCREEN ART PREPARATION, step 1) as your reference.
5) When the paper is in position, lift frame carefully without moving the print.
6) Tape registration crosses to the baseboard flush against both bottom corners of the print as you did for the first color run (see above, step 8). As before, this will make it easier to register the remaining copies. Do not, however, rely entirely on these registration guides. Visually check each print and make whatever adjustments are necessary to align the images before pulling the ink across the screen.
7) Follow the printing technique described in The First Color Run.
Proper clean-up is one of the most important steps in the silkscreen process. A screen that is well taken care of may be reused again and again. Stencils may be removed and replaced several times before it becomes necessary to restretch the frame.
• Washing the Screen: Water-Base Inks
1) As soon as you are through printing, scrape any excess ink off both the squeegee and the screen.
2) Remove pins from hinges and separate silkscreen frame from baseboard. Replace pins into baseboard hinges so they will not get lost. Set baseboard aside. It should not need to be cleaned.
3) Wash squeegee thoroughly under running water to remove all traces of ink. Shake off excess water and set it aside to dry.
4) Rinse screen well under running water.
5) Wet two large rough-textured rags and apply laundry soap.
6) Stand the frame on edge at a right angle to your body so that you can work on both sides of the screen at once.
7) Scrub the screen well between the two soaped rags to loosen and dissolve ink particles.
8) Rinse frequently under running water to wash away loosened ink particles. Frequent rinsing will also enable you to check your progress periodically.
9) Repeat scrubbing and rinsing until all traces of ink have been removed. The stencil should remain intact.
10) Allow screen to dry thoroughly before reattaching it to the baseboard.
• Washing the Screen: Oil-Base Ink
1) As soon as you are through printing, scrape excess ink from both the squeegee and the screen.
2) Separate frame from baseboard. Set baseboard aside.
3) Thoroughly saturate a large rag with turpentine and clean squeegee. Wipe dry with a clean cloth.
4) Set frame, screen side down, on several thicknesses of newspaper.
5) Again, thoroughly saturate a large rag with turpentine and scrub screen well using firm pressure. As the newspaper becomes soiled with dissolved ink, discard the top few layers and repeat the scrubbing process. As the scrubbing rag becomes saturated with dissolved ink, discard it in favor of a clean one.
6) For stubborn areas, stand the frame on edge and use two rags soaked in turpentine to scrub both sides of the screen at once.
7) When all the ink has been removed, rinse screen well under running water. Scrub with soap and rinse again. A well-adhered stencil, being lacquer-base, should remain intact.
8) Allow screen to dry thoroughly before reattaching frame to baseboard.
• Removing the Stencil
Stencils which have been taped to the screen should be removed and discarded before cleaning the ink from the screen. Blue film stencils are lacquer-base and therefore soluble only in lacquer thinner. A blue film stencil may be removed according to the following procedure.
1) Detach frame from baseboard. Set baseboard aside.
2) Set frame, screen side down, on several thicknesses of newspaper.
3) Thoroughly saturate a large rag with lacquer thinner and scrub screen well using firm pressure. As the newspaper and rag become soiled with the dissolved stencil, discard the top few layers of paper and exchange the soiled rag for a clean one.
4) For hard-to-remove spots, stand the frame on edge and use two rags soaked in lacquer thinner to scrub both sides of the screen at once.
5) Hold the screen up to the light to make sure that the mesh is clear and clean. You will still be able to see the stencil image because the individual fibers that make up the screen frequently become stained. This is not a problem so long as the mesh itself is not blocked.
6) After the stencil has been completely removed, wash the screen with soap and water. Allow screen to dry thoroughly before reattaching it to the baseboard.
Nail polish is also soluble in lacquer thinner.
Wear rubber gloves to protect your manicure.