Photolithography – a history and its process

Angela Young describes the background of photolithography and shows, step by step how to make a print.

Alois Senefelder invented the printmaking process of lithography in 1798. From its beginning, according to the College of Technology’s Digital Media Program’s article The History of Lithography, it has become one of the largest industries in the United States – a part of the Printing Industry, which is the third largest manufacturing industry in the United States.

Alois Senefelder started out his career as a successful playwright. Several of his works were published; however, he found it expensive to reproduce copies of his plays. In an attempt to reduce the publication cost, he tried to produce his own copperplate engravings. In the late 1700s copper plates were mostly used in printing, but it was a difficult process to create images and text to be printed in reverse (Jezek 1). In order to reduce cost and time, Senefelder decided to practice his engraving on slabs on Bavarian limestone instead of expensive copper. To correct mistakes made on the limestone, he found that a mixture of wax, soap, lamp-black and rainwater were efficient (The History of Lithography 1).

Through experimentation, Senefelder discovered that when he drew on the limestone with the correction fluid, the drawn image would repel water, while the surface of the stone where no image was drawn would hold water.

“He found he could first wet the entire stone then apply ink, with a roller, to the entire stone to replenish the ink on the image”

(The History of Lithography 1). The stone itself, which held water, would repel the ink, and the correction fluid, which is greasy and repels water, would accept more ink. Since lithography is based on a chemical principal, Senefelder decided the call the process chemical printing.

In 1826, Joseph Niepce, a French scientist, produced the world’s first photograph. This discovery eventually lead to the use of the halftone process (the act of breaking down the original photograph into dots of varying sizes that would be suitable to press reproduction). Henry Talbot used the first halftone screen used for the reproduction of photographs around 1852. About 33 years later, Frederick Ives, an American, designed the first practical halftone screen that consisted of two exposed glass negatives with line scribed on each of them. They were then cemented together so that the scribed lines would cross at right angles (The History of Lithography 2). This halftone process allowed the reproduction of original photographs without the need to draw or engrave them onto a printing plate.

Photolithography is a process by which images are photographically transferred to a matrix (either an aluminum plate or, less frequently, a stone), and then printed by hand (Devon 183). The French printers Alfred Lemercier and Alphonse Poitevin first started experimenting with photolithographic techniques in soon after the discovery and use of the halftone process. Their early experimentations, however, were not reliable enough for commercial use. Photoengraving was the industry standard until offset lithography became commonly used for reproduction in the mid-1900s (Deven 183).

Most typical black and white photographs are “continuous tone” (as seen in the following example image), which means they are made of a full range of pure whites to deep blacks.

Because most printing process cannot reproduce a continuous tone, it must be mechanically re-created. This halftone technique can either be achieved by superimposing a halftone screen over the image before it is exposed or by creating a dot pattern when you print the image out from the computer to a transparent film.

In my personal research I used a computer with Photoshop CS3 to create a dot pattern on my image and printed it out on three different transparencies to a LaserJet 1160 Printer. I also found that in order to achieve an even black to areas in your image when you print them, it is best to experiment by adding noise to those black areas using Photoshop; I found it worked to add 10% noise to the black areas in my image. I then exposed each transparency in a light table to a photolithographic plate in increments of 20 seconds (starting at 120 seconds and going up to 200 seconds) to see which time and which transparency best produced a full range of values from lightest lights to darkest darks. Although expensive to purchase, at approximately $150.00 per roll, I found that Pictorico transparency film worked best to reproduce the image I used and gave me the widest range of value.

I have included a step-by-step guide on how to print out a transparency using the LaserJet 1160 Printer, how to expose that transparency to a photolithographic plate and how to print that plate using a lithographic press.

Printing Your Film to Hp LaserJet 1160 (as taken from Mary Hood’s class Handout)

Print Menu Selections

Click on File in top Menu

a. Print Preview: Color Management

i.Source

  1. Document: grayscale (I also found that printing Black Only worked as well)

ii. Print Space

  1. Profile: Working Gray – Dot Gain 20%
  2. Intent: Perceptual
  3. Black Point Compensation

iii. Page Set Up

  1. Setting: Select if using custom paper size
  2. Paper Size: Tabloid
  3. Format: HP LaserJet 1160
  4. Select page / image orientation; Portrait
  5. Scale: 100%
  6. Click OK

Print Preview Menu

i. Output

  1. Please note: The printing directions are for the LaserJet 1160 printer but the photographs show the DesignJet 500

    Screen
    a. Unclick “use default screen”
    b. Frequency 85 lpi (this creates the halftone)
    c. Angle: 45
    d. Shape: choose shape of dot (found that ellipse works best)
    e. Click OK
  2. Check Output Options
    a. Calibration bars
    b. Registration marks
    c. Corner crop marks
  3. Click Print! (Example image right)

Make sure to check your image with a loop or magnifying glass to see that you have a dot pattern that will work for your image. Once you have the image the way you want it to look on the transparency you are ready to expose it to a photolithographic plate. It is best to take notes on any changes that you made in the printing process. Remember, the image will expose to the plate EXACTLY how it appears on the transparency so be careful not to smudge the ink or put fingerprints on it.

Exposing the transparency to a photolithographic plate

Materials Needed:

  • Photolithographic Plate
  • Film Transparency
  • Light Table and Exposure Unit
  • Soft Scrub Brush
  • Gloves
  • Apron
  • 3-Way Plate Developer
  • Newsprint
  • Clear Tape
  1. Make sure the light exposure unit is completely clean and dust free. (Example image right).
  2. Take out your Photolithographic plate (make sure to keep the light sensitive plate under a yellow or red safety light until it is completely exposed).
  3. Attach your film transparency FACE DOWN (emulsion to emulsion) to the plate with small pieces of clear tape. Rubylith can also be used to cover your margins to ensure clean printing.
  4. Place the plate and film in the exposure unit face up. Close the lid of the exposure unit and turn on the vacuum sealer until the dial reaches between 20 and 25 PSI.
  5. Turn the expose unit vertically so that the UV light unit will evenly expose the entire image. (Careful when lowering the exposure unit!)
  6. Turn on the UV light unit and let it warm up for a few minutes. Calculate how much time you are going to expose your image for (through the step wedge process, I usually start with 90 seconds and add more time from there) and punch that time into the light integrator.
  7. Press START! (It’s best to leave the room to protect yourself from UV rays).
  8. When the light unit turns off, take the plate (minus the film) into the dark room next door. Remember to keep the plate under safety lights until you are done exposing.
  9. Place the plate on a plexi-glass support over a sink and using a dry soft scrub brush, pour a small amount (about an ounce or so) of 3-Way Plate Developer (which can be purchased at www.takachpress.com) directly onto the scrub brush. WATER SHOULD NEVER TOUCH THE SCRUB BRUSH AT ANY TIME. Do not get water on the plate until you are done developing it. WEAR GLOVES.
  10. Go over the entire plate with the scrub brush filled with the plate developer for approximately 5 minutes. Replenish the brush with plate developer if the brush starts to stick to the plate.
  11. When you can fully see your image on the plate, place the plate under running water to rinse off the plate developer.
  12. As soon as your plate is fully washed off, blot the plate dry with newsprint. DO THIS QUICKLY. If you do not completely dry the plate and leave standing water on the image, the water will burn into the image and will show up when you are printing.
  13. Post expose the plate by itself in the light unit for 30 seconds to harden the image and you are ready to print!

Printing a photolithographic plate

Materials Needed:

  • Litho Press
  • Plate Support
  • Scraper Bar
  • Tympan and Grease
  • Finishing Gum
  • Gum Arabic
  • Apron
  • Gloves
  • Rags
  • Litho Ink (Shop Mix Black)
  • Magnesium Carbonate
  • Composition Roller or Leather Roller
  • Litho Inks
  • 2 Clean Bowls, one for water and one for dirty sponge water
  • 2 Clean Fine Pore Sponges
  • Putty Knife
  • Razor Scraper
  • Paint Thinner
  • Cheesecloth
  • Masking Tape
  • 1 You will be using a litho press to print your plate. Make sure you have a plate support that is completely level and even on the press bed. This ensures even printing pressure over the entire image. Also make sure to use a scraper bar that is larger than the image but smaller than your printing paper. Your scraper bar should start and stop ON the paper but OFF the image.

    2Attach the plate to the press support with a small amount of Gum Arabic. Set your desired pressure and mark your start and stop points on the press with tape. (See image)

    3 Roll out your ink slab. Make sure to use a roller that will cover the ENTIRE image. I like using Shop Mix Black with a little Magnesium Carbonate mixed in it for proofing and also printing if you want to use black. Any color can be used to print but make sure it’s pretty stiff ink. If the ink isn’t stiff enough, your image with fill up with ink too quickly.

    4 Apply a small amount of water to the plate and quickly wipe the entire surface to achieve a thin tight film of water. It is extremely important to keep the water on the surface of the plate THIN or you will get water burn in the image.

    5Roll over the image with either your composition or leather roller 3 to 4 times. Re-charge the roller on your ink slab, wet the plate with a thin film of water and repeat the rolling process so that you have about 3 to 4 total passes of 3 to 4 roll ups. The image shouldn’t fill up with ink on your first pass! You want to slowly build up the ink surface so the image doesn’t scum up. (See image)

    6 Lay a sheet of newsprint over the image and run it through the press. This is called a PROOF. You should have about 5 to 10 proofs on newsprint before the image is completely full of ink and ready to be printed on good paper.

    7 When finished printing clean up the area with paint thinner and soap and water. If you want to keep the plate to re-use it later, blot excess ink off with newsprint, and clean off the plate completely with a mixture of paint thinner and water. When the plate is completely free of ink, poor a small amount of Finishing Gum on the plate and buff down tightly with cheesecloth.

    From left: examples of a film transparency, the image shot onto a photolithographic plate and the image proofed on paper.


    Troubleshooting

    I have found that when printing photolithographic plates, they tend to want to scum up in the margins with ink. To get rid of this you can either do a snappy pass with the roller to pick up the ink or use a little plate developer in the area that keeps picking up ink. Let the plate developer sit on the trouble spot for a minute then wipe it clean with water and paper towel. DO NOT let plate developer get into you image area!


    Bibliography



    2 Comments

    1. ravi
      Posted December 12, 2011 at 7:21 am | Permalink

      Hello,
      Thanks for your postings, and it is really wonderful article.
      I have few doubts during transfering any image.
      1) if i want to transfer any texture on to cylindrical pipe or cavity of any mould what media ( photo tool , printed film ) should i use to transfer?
      2) how should i transfer those texture on cylindrical or odd shape for chemical etching?
      Please kindly guide.
      Best Regards
      Ravi

    2. alan Luft
      Posted February 13, 2012 at 7:04 pm | Permalink

      I’m trying to use non-toxic methods for stone lithography, specifically for a xerox transfer. I’ve had some success using a combo of citra-solv and soysolv, but the method is not as consistent as I would like.

      Please advise.

      Thanks,

      Alan Luft

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