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All Handouts for this class

By Timothy Hill,2014-11-28 12:45
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All Handouts for this class

ART 2130 Silkscreen

    Christie Nuell

    Table of Contents

    The Photosilkscreen Process 2

    Creating Stencils for Photosilkscreen 5

    Color Separations in PhotoShop 8

Setting up to Print 10

Registration Methods 10

Crayon Resist Method 12

    Drawing Fluid and Screen Filler 14

Cleaning your Screen 15

Permitted Paper sizes for the Laser Printer 16

Matting and Mounting 17

    A Bibliography for Printmakers 18

Art 2130 Silkscreen 1. 11/28/12

    Christie Nuell

The Photosilkscreen Process

General Information:

    At MTSU we use a Direct Photoemulsion. This is a liquid that we apply directly to the back of the screen.

    We use Autosol 6000 which is formulated for acrylic and waterbased inks. The emulsion and the sensitizer are mixed together and a little water is added. The emulsion is refrigerated for a longer shelf life.

    The photoemulsion is LIGHT SENSITIVE. While you may coat your screen in the studio with the lights on, it must be dried in the darkroom, with the doors shut. You may go in and out of the dark room while it is drying, but otherwise keep the doors shut. The orange safe light in the large exposure unit is harmless and will provide you with some light to see by. The overhead light may be flipped on briefly, but should be turned off again.

    The emulsion is LIGHT HARDENING. That means that light makes it harder and tougher. Eventually it becomes almost as tough as epoxy. Sunlight and heat will harden the emulsion. Thus it makes good sense to reclaim the screen with bleach and hot water after you have printed. Emulsion left on a screen for weeks or months may be impossible to remove.

    This process is suitable for what is known as "line art". It is not suitable for images which rely on "continous tone".

The Process:

    1. Your screen should be clean and dry. For solid flats, 170 mesh is good, for detail

    work, 220 mesh or higher is best. Make sure all old emulsion is removed, especially if

    it is in the printing area.

    2. Choose a scoopcoater that is at least 3 inches narrower than the fabric area inside the

    screen. This is necessary to get a thin even coating.

    3. Take emulsion out of the fridge. Pour some into the scoopcoater, less than half full. 4. Prop the screen against a counter or table with the outside or back facing you. 5. Start about an inch higher than where the fabric meets the wood, and hold the

    scoopcoater against the fabric with the thin edge touching the fabric. 6. Pressing against the fabric, tip the scoopcoater forward until the emulsion flows to

    and touches the fabric.

    7. Slowly pull the scoopcoater up until you are 1" from where the fabric meets the wood

    at the other end of the screen. Tip the scoopcater back so that the emulsion starts to

    flow back into the scoopcoater. Remove the scoopcoater with a final upward lift. 8. Check that the coating is even and use a discard to redistribute any thick areas of

    emulsion, especially at the edges or if you have tiny bubbles showing on the surface. Art 2130 Silkscreen 2. 11/28/12

    Christie Nuell

    9. Put the coated screen to dry in the dark room, making sure nothing comes in contact

    with the emulsion.

    10. Dry the screen for 20 minutes using a fan. [Drying times vary according to how

    successful you were in getting a thin even layer of emulsion on the screen. In any

    case you want to coat the screen and burn it in within an hour. Don't let unexposed,

    coated screens sit overnight or for long periods of time]

    11. Check that the screen is dry. Be careful of thick areas which may have a dry skin over

    a wet area, as they will completely fall out after the screen is exposed.

Exposure:

    If using the Douthitt exposure unit, turn the power switch on 5 minutes before using it.

     Exposure Times: Douthitt = 4.0 light units

     Polylite = 20 seconds

    1. Clean any emulsion, dust or ink off the glass of the exposure unit, being careful not to

    scratch the plate glass.

    2. Put your stencil face up on the glass of either the Douthitt or the Poly Lite (very large

    exposure unit).

    3. Put your dry, coated screen on top of the stencil, so that the fabric of the screen is in

    direct contact with the stencil.

    4. Loop the rope across the top of the screen. This allows the vacuum to work inside the

    screen frame. Make sure the rope does not hang down around the edges of the

    vacuum unit (rubber blanket area)

    5. Close the top of the exposure unit (lid with rubber blanket)

    6. Turn on the vacuum.

    7. Check that the vacuum is working correctly either by looking at the dial or by a visual

    check of the appearance of the shape of the screen in high profile under the rubber

    blanket.

    8. On the Polylite, turn the timer at least half way and then use the clock to time 25

    seconds of exposure, Turn it off manually.

    On the Douthitt, use 2.4 time units. This will go on and turn off automatically.

Immediately proceed to Wash Out Step:

    At this point the screen is vulnerable. If there are people using the screenwash sink, you should leave the screen in the dark until the sink is available. However, you need to do it as soon as possible - don't go eat lunch while you wait!

1. Place the screen in the sink with the BACK facing you.

    2. Use the hose and spray (NOT the pressure washer) and cold water. Spray a delicate

    fan-shaped jet of coldwater all over the back of the screen

    3. Turn the screen around so the front is facing you. Spray with cold water and the

    image areas of the screen will start to open up. This may take a few minutes and will

    require your careful observation. The only way to be sure an area has washed out Art 2130 Silkscreen 3. 11/28/12

    Christie Nuell

    successfully is to hold the screen up to the window or the light to see the area is

    totally clear. It is important to get all image areas washed out of the screen at this

    point as otherwise you will need to remove the emulsion from your screen and start

    the whole process over!

    4. When you are sure the image is fully washed out, give the back of the screen a final

    quick spray and then set the screen to dry. Don't leave it sitting out if you are leaving

    the studio. Use the racks in the dark room.

One Last Thing:

    Before printing you will want to hold your dry screen up to the light and check for pinholes (specks of dust that have become part of your image). There are two ways to stop these out:

    ; Emulsion applied very thinly with a tiny brush and dried for several hours ; Small pieces of Scotch Tape? (red plaid box) applied to the back of the screen. Keep

    all tape away from areas that will print

    If you have large areas up and down the sides of the screen that are not filled and you wish to contain the printing ink, use masking tape applied to the BACK of the screen. KEEP THE TAPE 1" AWAY FROM PRINTING AREAS as the thickness of the tape can create real problems. NEVER use tape as a substitute for emulsion in the image area itself!

    This diagram below is true for all screen printing techniques. Don't try to print an image larger than your screen can accommodate. It has to do with the different tension of the fabric as it gets closer to the wood.

Screen Frame

    3" MINIMUM

    margin between wood

    and edge of printing Largest area area possible to print

    with this screen

    4"

    Art 2130 Silkscreen 4. 11/28/12

    Christie Nuell

Creating Stencils for Photo-Silkscreen

Different substrates can be used. They important thing is that they should be transparent

    (preferably) or at least very translucent.

    The nice thing about silkscreen is that you use positive stencils (that is, blacks and whites

    are not reversed as is the case with photographic negatives), and the stencil is also burned in the right way round, so that any text or numbers will appear so that you can read them properly.

Wet Media Acetate:

    Use black ink and a brush, technical drawing pen or holder with removable nibs. The

    important thing is that the ink should be very opaque, which you can test for by holding it up to the light. *Most felt-tip pens or other writing implements with self-contained ink sources will not work well enough for this process. Sponges, toothbrushes for "spatter" effects and other non-traditional drawing techniques also can be used with the ink.

Tracing Paper:

    The same materials and restrictions apply as to working with wet-media acetate. However, dry media also work well, such as ebony pencil, 4B pencil, charcoal, conté

    crayon, litho crayon, and grease pencil.

    Make sure you make dark, opaque marks. Delicate marks may not come out when you expose the stencil onto the screen.

    Frottage (rubbings) work well with litho crayon and tracing paper.

Copy Machine Stencils:

    You can make copies of images or drawings that you have made onto special copier

    acetate. This is a special type of film that you can obtain from the instructor and run through the copy machine as if it were a piece of paper. Please do not try to use any other type of acetate or film in a copy machine as it will melt inside the machine and cause damage.

Paper Stencils:

    Use the Hewlett Packard bond on the roll in the Paper Room (354D) to make great stencils from the laser printer. You must cut the paper down to one of the permitted sizes for the laser writer (posted on the wall above the paper). After printing rub baby oil gently into the paper with a soft rag to make it translucent, and use it as a stencil. Please be careful when feeding the paper into the Elite laser printer.

Laser Printer Stencils:

    Stencils can be created on a computer and printed out onto laser printer acetate or copy

    machine acetate. I can provide it. Do not use transparencies for inkjet printers, or any other kind of acetate which may melt inside the machine. Don't use resolutions higher than 125 ppi for your stencils if they will produce a stencil with halftones. Illustrator files print beautifully. Fo line art from Photoshop use 300ppi resolution to get nice curves. Remember it may be better to use the copy machine for line art than to scan an image in and print it out.

    Art 2130 Silkscreen 5. 11/28/12

    Christie Nuell

Found Objects:

    Any flat, opaque object can be used as a stencil against your coated screen, as long as there are no sharp parts which might pierce either the fabric of your screen or the rubber of the top of the exposure unit. Students have successfully used fabrics, construction paper, gaskets and other suitable objects to directly create stencils.

Amberlith:

    The best way to create flat solid areas, checkerboards, or any stencil which has several areas of the same flat color in different parts of the image, is to use amberlith. Amberlith has two layers: a thin orange film, and a thicker clear acetate backing. It is translucent, so is excellent for tracing over working drawings, or even partially completed prints. Always lay the acetate side down against your drawing, so that the orange film, which you cut, is on top. Use removable tape to tape it to your drawing. Apply only enough pressure to cut the film layer: don't cut through the acetate as it is the backing that holds it all together. Strip away the orange film in the negative space, and leave it where you want the stencil to print the color ink you will be using. Try to conserve

    the amberlith: you may not need to cut off a piece from the roll that is as large as your image if the area you will be printing is only a fraction of the image size. Large stencils can also be recycled to create smaller ones.

Wide Format Printer:

    We have a 24” wide Epson printer that can print large stencils (roll-fed) from a digital

    file. Please don’t do this without checking with me. Remember the largest you can

    print is 3” in from the wood of your frame on each side.

General Tips:

    1. Pens you normally would use for writing don't make good stencils on tracing

    paper or acetate. If you like the mark they make, use a copy machine to create

    your stencil from a drawing on paper.

    2. It is not a good idea to create all your stencils before you start printing. One or

    two, perhaps, but if you try to make them all you deny yourself the benefit of re-

    thinking colors or approaches as you are working on the print.

    3. Stencils of different types can be taped together with transparent tape. If you do

    this, always tape the underneath of the stencils together, so that no tape comes

    between your stencil and the emulsion on your screen while it is being exposed.

    Tape doesn’t work well on baby-oiled paper.

    4. Remember that colors printed over each other produce colors that you haven't

    mixed as ink. By planning ahead, shadows and/or highlights can be printed by

    planning where the stencils for two printed colors will overlap. This means that

    you can get a much richer, more detailed printed image without having to create Art 2130 Silkscreen 6. 11/28/12

    Christie Nuell

    any extra stencils and print them.

    5. Your screen size determines the size image you can make. Subtract 6 inches from

    the inside dimensions of the screen, and that is the largest stencil that screen will

    successfully print. Remember to leave about 4 inches between the edge of the

    stencil and the frame itself when positioning stencils to expose onto your screen. Art 2130 Silkscreen 7. 11/28/12

    Christie Nuell

Color Separations for Photo processes in Printmaking, using Adobe Photoshop

    Images can often be scaled in the software, or tiled, so that you are not confined to printing on a 8 1/2 by 11 inch format.

For color separations:

    1. Scan the image and import it into a program such as Adobe PhotoShop.

2. Under "Mode", click on CMYK (Process Colors)

    3. Open your Channels window, by selecting "Palettes" under the Window menu, and going to "Show Channels."

    4. Select the Cyan channel only, select all, and copy the channel for Cyan.

    5. Create a New File for each color, and paste the contents of that channel into it.

    6. Give your new file a name that contains the color it represents (e.g."MypictureCyan")

    7. Under "Mode", convert this new file to a bitmap. This will make a black and white version which can be printed out and burned into the screen. Experiment with different forms of dithering, and different resolutions (dpi) to print.

    8. Repeat steps 3 through 7 with the magenta, yellow and black channels of the original scanned image.

    9. Print the files, choosing "labels" and "registration marks" under Options in Page Setup, under the File menu. Under the "screen" button in the same dialog box, insert these values to help avoid moiré patterns if you are printing half-tones:

     Cyan 75

     Magenta 15

     Yellow 0

     Black 45

    You can print a negative or positive image, depending on your needs. They may be directly printed to laser printer acetate, or to paper, using a copy machine to put onto acetate.

    10. When you prepare your paper or other printing substrate, put some of the Scotch blue-plaid removable tape on areas where the registration marks will appear on each Art 2130 Silkscreen 8. 11/28/12

    Christie Nuell

    surface you'll print on. That way you can use the registration marks, and then peel off the tape without scarring the print after you have finished printing all colors. Inks.

    Process colors are available in most brands of printmaking ink, and you can print your stencils with the appropriate Cyan, Magenta Yellow and Black inks. You may want to print with other colors, or with an ink other than the "correct" colors for some interesting effects. You may want to mix them with a Half-Tone Base, which is oil based. Hunt-Speedball acrylic process colors actually will mix with Advance Half-Tone base (oil-based), but you need to use mineral spirits or paint thinner to clean out the screen.

Caveats:

    • The size of the opening in the mesh of most screens does not allow for very fine dots, and the ink tends to spread on the paper as it is being printed. The half-tone base helps greatly to stop it from smearing. Coarse dithering or dot patterns print best.

    • Aesthetically speaking, if you have a color photograph you like and simply want to make a screenprint out of it, you'll probably be disappointed with the results. It might be better to use this procedure in conjunction with stencils created other ways, and create something which does not attempt to mimic a photo.

• Scanners can be useful in in-putting images to the computer for manipulation and

    producing color separations. Surprisingly, for many purposes, a copy machine with an adjustable scale calibration works better and is lots faster, especially for black and white work. Scanned black and white images often replace graceful curves with jagged, pixellated lines. Only use special copier acetate in a copy machine or laser printer. Other kinds of acetate are apt to melt inside it, causing it to quit working.

Art 2130 Silkscreen 9. 11/28/12

    Christie Nuell

    Setting Up to Print

    1. Discard System of Registration:

    When using discard system, be sure that you have at least 2" between the edge of the

    discards and the edge of the printed area, represented by the dotted rectangle on the

    printing paper.

    Tape attaching chipboard to Your Screen securely printing board clamped to the screen board 4 discards One long

    taped down, to piece of

    Printing paper enclose one Printing board tape

    corner of attaching

    paper. This set acetate to

    up for right chipboard

    handed printer. as a hinge Printing board Tape should be

    applied close

    to the edge the

    paper will rest

    against.

    chipboard

    Art 2130 Silkscreen 10. 11/28/12

    Christie Nuell

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