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Polyester Plate Lithography

The source of this text is from:
(www.nontoxicprint.com) by Friedhard Kiekeben, Associate Professor at Columbia College Chicago
GEORGE ROBERTS developed Polyester Plate Lithography, a new and nontoxic form of lithographic printing while he was Professor of Printmaking at Boise State University. George sadly died of cancer in 2001.


Emily McCoy, polyester plate lithography collage, Chicago 2010

Today many artists, print shops and art schools
are adopting this very straightforward lithographic method
for the creation of unique and limited edition
artist prints, books, and installations -
all without the need of the harsh and
unhealthy chemistry of lithography as we knew it.
Used by artists and designers
the creative scope of the method is virtually unlimited
.

Polyester Plate Printing started as a low cost yet professional form of commercial offset lithography. CMYK plates are made straight from the desktop and often thousands of copies are printed from these as business cards, pamphlets, posters, and the like. The medium, also known as Pronto Plate Lithography, is capable of reproducing the full spectrum of lithographic marks such as: hand drawn brush strokes, ink wash, texture, crayon and pencil marks, and is equally well suited for digital imaging. Plates can be also imaged directly with a laser printer or a photocopier. In both cases, plates should be heated to produce a stable lithographic printing surface. Although still relatively unknown the medium is set to become one of the most popular forms of printing.

The process is more straightforward than conventional lithography as the plate does not require chemical processing in the form of etching with nitric acid etc. Some print shops still use fountain solution and strong acids for printing and processing, but the samples shown here are all made without the addition of harmful chemicals such as glycol ether or plate etching chemicals. The most common problem encountered when printing a polyester plate is "scumming", when the plate starts picking up ink in areas where it is not wanted. Our solution is simply to use a wiping solution that is fortified with a small amount of gum arabic and a sprinkling of citric acid (both are safe staples of the food industry). The gum makes the plate more ink loving, and the citric is particularly helpful in preventing scumming, and ensures a clean print.


Lindsey Strawn rolling up a pronto plate, Columbia College Chicago.

The clarity of the print is largely determined by the consistency of the ink. An ink that is too soft and viscous (oily) will result in smudging, while a very stiff ink gives a crisp mark, but makes a heavier demand on the durability of the plate. An overly stiff ink may even rip toner marks or other drawing media off the plate during rolling up. As a remedy, use a softer ink and ensure an amount of heat curing before printing. As most of the drawing media used in Polyester Plate Litho are akin to the materials used in ACRYLIC RESIST ETCHING, many of the requirements are similar. Acrylics like heat to aid polymerization, and the new litho process is no exception.

 

Bernadeta Szopinska. polyester plate lithograph made using a range of oil and litho crayons, Sharpie, ballpoint pen, and acrylic wash media Columbia College Chicago, 2008

Traditional Lithography

When Alois Senefelder invented lithography in 1798 it represented a genuine innovation in the repertoire of printmaking techniques. Existing methods, such as etching and relief printing, used various means to produce a shallow relief to take the ink that would then create the final image. Senefelder’s method was fundamentally different: the flat printing surface was porous as well as water loving, and the image was formed by applying greasy media to a stone. The printing process took advantage of the fact that grease and water repel each other. When greasy printing ink was applied with a roller, it stuck to the deposit of greasy tousche or crayon but was repelled by the moistened surface around these marks.

In traditional lithography, this basic methodology is enhanced through highly complex and finely tuned chemistry involving the use of tar, tallow, acids, soaps, solvents, and so forth. Unfortunately, many of these very things are detrimental to health, and elaborate safety measures are needed to practice this type of lithography with any reasonable degree of safety.

Nontoxic Lithography

Polyester plate lithography has the advantage of being a user friendly, accessible, and safe printmaking method. Initially designed as a cheaper alternative to aluminum plate offset litho in commercial printing, it has now been embraced by the printmaking community.

Since its introduction in the late 1990s polyester plate lithography has become increasingly popular with artists and educators experimenting in the medium of lithography, and for the production of small to medium sized editions of lithographic prints. In many ways, the nontoxic process is less complex than traditional methods of stone and metal plate lithography.


Laura Shields, polyester plate lithograph

The materials and equipment needed for polyester plate lithography are easy to obtain. Printmaking suppliers stock polyester plates (e.g. Pronto Plates), and the required drawing media are commonplace. Any etching press can serve as a lithographic printing press. Even printing by hand is possible with polyester plates: ink the plate, place it in contact with the well-dampened paper, and rub thoroughly from the back with the back of a wooden spoon to make the impression.

Many artists are familiar with the process in connection with xerographic plate making, where the image is derived from a photocopy or laser print. Polyester plate lithography is equally capable of reproducing an extensive and expressive range of hand-drawn marks, lines, washes, and reticulations. The medium can be mastered within hours, and the resulting prints have a fresh and vibrant feel that is genuinely lithographic in character.

Lithographs often exhibit a lightness of touch and a likeness to the medium of drawing: polyester plate lithographs convey this aesthetic beautifully, and with ease.

(above) Antony West, polyester plate lithograph

(below) John Donatowicz, polyester plate lithography drawn with a ballpoint pen, 2010

Direct Drawing on a polyester plate

MATERIALS
Products and equipment needed to draw on a polyester plate:

  • Polyester plates e.g. Pronto Plate
  • Waterproof Sharpie pens (various thicknesses)
  • Ballpoint pens

Two tried and tested utensils for drawing lines on polyester plates are waterproof Sharpie pens (also try the new Paint Sharpies which give added opacity) and regular ballpoint pens. These types of pen are great for creating delicate yet solid lines, swirls and hatchings and allow you to achieve a pictorial quality akin to pen and ink on paper. The marks print well and stay reproducible throughout an edition of prints.

To get a fuzzy, crayon-like line it is best to use the hardest kind of lithographic crayon, such as Korn's litho crayon No 4. Press down firmly when drawing to get reproducible marks. Do not use soft litho crayons or pencils as the marks made by these will fade or wash away when printing. Crayons made from resins, acrylics, or hard wax should be ideal for resisting wear and would be ideal for this method.

For the best results (with the exception of greasy media), heat-set any drawn and painted marks using a hairdryer.
Be careful not to get grease on your plates while working - even fingerprints may print!

Painting on a polyester plate

Because acrylic surfaces possess lithographic adhesion, just as greasy surfaces do, oil-based printing ink will stick to acrylics during roll up and then print as a crisp mark. Many acrylics can serve as lithographic resist, but it is important to thin the ink sufficiently to avoid any excessive build up (i.e. ink deposits standing in relief) on the plate. Thicker layers of acrylic will cause the ink roller to skip across the surface, and you will only get a partial impression. I would recommend using any of the following three acrylics as a base for your ink.

MATERIALS

Products recommended for painting onto a polyester plates

  • Golden Acrylics GAC 200 medium (Polymetaal art.nr. 026229)
  • Hunt Speedball Screen Filler (Polymetaal art.nr. 014100)
  • Lascaux 2060 clear gloss varnish (Polymetaal art.nr. 026208), or Lascaux hard resist (Polymetaal art.nr. 026210)

Once you have thinned the acrylic with 20% to 30% water, add some india ink for opacity. Use soft brushes to paint solid blobs, stripes and graphic areas onto the plate. Creating your image is simplicity itself - working on a Pronto Plate is hardly any different from painting or drawing on paper.

One of the great advantages of lithographic drawings is the ease with which you can work in the reverse. Once lines and brush marks have dried, use an Exacto knife or cutter to draw white lines or hatchings into the dark areas. You can also lighten areas by scraping off the ink.

It is best to work with a solid but not thick layer of opaque ink. Avoid thin washes as any acrylic mark, however thin, will print as black. Tones, washes, and reticulations are achieved by other means. Some acrylics tend to chip off the plate during printing. These chipped areas can often be touched up. Avoid curling the plate during roll up or excessive handling to help avoid chipping.

METHOD

Random reticulated effects are easily created using a wet on wet technique:

  1. Make up a strong solution of dish-soap and pour it into a plant mister.
  2. Paint the plate surface with acrylic.
  3. Spritz with the soap solution.
  4. Use a hair dryer or hot plate to dry the plate.

Once dry, this results in surprisingly varied and detailed reticulations. (TIP: Acrylic washes easily overfill with ink when charging the plate. Ink washes can be lightly scraped with a blade or fine steel wool to make the fine textures more reproducible, even on a fully charged plate.)

For aquatint-like tonal gradations, use an airbrush, or simply spatter ink drops using a diffuser or a toothbrush.

To make a tonal wash medium, dissolve a few teaspoons of photocopy toner in ethanol alcohol, mix with some dish soap, and paint onto the plate. The fine toner particles distribute themselves within brushstrokes, giving the desired grainy tone.

Many simple tools can be used to create texture and expressive areas of tone. Dip pieces of sponge, a toothbrush, tarlatan, or crumpled up paper in acrylic and carefully stamp on the plate to make textures.

SAFETY NOTE: Be sure to wear a dust mask and gloves when handling toner. Toner particles should not be inhaled.

Toner-based marks, in particular, require heat-setting to bond with the plate. For the best results, place your plate on a hot plate for about 30 minutes before printing. Alternatively, use an iron to heat set the plate.

Other options for creating reticulated 'lithographic' wash effects:

Work with the Orono Ground mixture and create washes by diluting with water (the plate must be dry before printing). Or, use a commercial wash medium such as the LASCAUX TUSCHE wash. Or, don't work on the actual matrix at all; some printmakers prefer to make tonal and reticulated drawings on paper and then generate the polyester printing plate by photocopying. This way, the drawing remains the "master" and plates can easily be reproduced if any wear occurs during printing.

Polyester Plate Printing

Polyester plates are easy to print. During printing, the truly lithographic nature of this method - utilizing the repulsion between grease and water - is revealed. Lithographic printing typically involves alternating between wetting the plate and rolling over it with greasy ink in multiple passes until the desired density of ink has built up. Also, as in commercial offset lithography, it is advisable to make a number of proof prints on newsprint before editioning a plate. A plate that undergoes repeated wiping, ink charging, and proof printing cycles becomes more ink loving and produces crisp and reproducible results.

METHOD

Wiping Water

  1. Fill a plastic bowl with water and add one shot glass (approximately 45 ml U.S.) of gum arabic solution and half a teaspoon of citric acid powder.
  2. Place the polyester plate on a clean, slightly wetted inking surface.
  3. Now dip a cellulose wiping sponge in the water, squeeze, and pass lightly over the plate a number of times.

The pores of the plate surface now fill with tiny water droplets that will repel the ink roller as it passes.

METHOD

Lithographic Ink

Some litho inks are very stiff and hard whilst others are as malleable as etching ink. Stiff inks are thought to give the best detail reproduction, but softer inks are easier to apply and give an image greater contrast. Oil-based etching inks are well-suited for printing polyester plates, but the ink may require the addition of a small amount of magnesium carbonate to stiffen it and to avoid scumming.

For a good black ink I would recommend Graphic Chemical litho ink No 1921, which has proved to be ideal for the polyester plate process. Very stiff inks are often modified with linseed oil; the litho varnish No 3, for example, will soften ink and make it easier to roll up.

Whatever the consistency, the ink needs to be worked around with a spatula for a few minutes. Scrape the ink across a 10 x 10 inch surface and then use a good roller (preferably a softer nitrile roller) to roll out the ink evenly in a criss-cross pattern. A well rolled-out ink makes a smooth sort of hissing sound while charging.

  1. Dispense some litho ink onto your inking surface.
  2. Use a circular scraping action inside the can to dispense the ink, then cover the surface inside the tin with plastic film to prevent it drying out.
  3. Modify the ink as required.
  4. Work the ink for a few minutes.
  5. Gently start rolling over the dampened polyester plate - you may need to hold down the edge of the plate to prevent it from curling over the roller.
  6. After each roll-up the plate needs to be gently re-wetted in order for the surface pores to remain ink-repellent.

It is rarely possible to charge a plate in one go. A well-charged plate usually requires the gentle and careful build up of successive layers of ink and water.

When a plate is freshly made, it may take from 4 to 10 ink and water cycles before it is fully charged with ink. However, once a plate has already printed, the surface becomes more ink loving and only a few inking-wiping cycles are needed to recharge.

METHOD

De-Scumming

Every now and then an inking pass will leave smudges where they should not be: this is called "scumming". To remove these areas during inking, some printmaking guides recommend the addition of fountain solution to the wiping water but, as this contains harmful glycol ether (anti freeze), I prefer the addition of citric acid as an anti-scumming agent. Simply dribble some of the wiping water onto the scummed areas and gently wipe with a sponge.

  1. Add ½ teaspoon of citric acid powder to the wiping water (water + gum arabic).
  2. Dribble onto areas where scumming has occurred.
  3. Gently wipe with a sponge

METHOD

Printing

Polyester plates can be printed on a litho press, but many artists prefer using an etching press. (Comment Polymetaal; the only reason Senefelder developed a special lithographic press, is the fact that his stones did break on an etching press, an etching press is not flexible enough to follow an uneven surface of a stone. Hence, offset plates (aluminium, zinc, polyester, etc.) can be printed very well on an etching press.) To print a polyester lithograph it is crucial to use little or no felt material between the rollers to gain maximum contact between plate and paper. I use one thin blanket of vinyl interfacing, and full pressure.

  1. Gently peel the inked plate off the slab and place it onto your registration sheet.
  2. Lay the printing paper on top as though printing an etching.
  3. Lower the blanket and roll through the press.

For a quick proof with good registration you may try inversion printing: lay the damp paper on the press bed, flip the polyester plate face down and register the plate directly to the sheet of paper.

Cleaning

To clean the plate, run it through the press a few times with newsprint to absorb excess ink, then wipe it with concentrated dish soap solution. (TIP: Use a ratio of around 1 part dish soap to 10 parts water to obtain a strong detergent that is powerful enough to dissolve any greasy ink residues.) Stubborn ink residues can be removed with toothpaste applied using a soft cloth. Clean the slab and rollers in successive stages using vegetable oil, baby oil, and detergent solution (in this order). Remember that, unlike VOCs, cleaning oils are non-volatile and act best if left to soak into the ink for a few minutes. Use a spatula to scrape off excess ink to save on cleaning rags.

To get good results in multi plate color printing it is particularly important to clean plates thoroughly after each printing stage, otherwise ink will be contaminated when recharging the plates. Use a three-step cleaning routine for each plate:

  1. Run off residual ink onto newsprint.
  2. De-scum the plate with wiping solution to remove ink offset from other plates.
  3. Dispense a blob of toothpaste onto a soft rag and use this to completely mop up any ink residues from the plate then clean and de-grease the plate with strong dish soap solution.

Make sure you are using separate sponges and separate wiping bowls for each color to avoid cross-contamination.

Papers for Polyester Plate Lithographs

Lithographs can be printed on a wider variety of paper than etchings. Slightly textured rag paper can enhance the lithographic grainy look of the print. Successful prints can be made on wet or dry paper.

If a print looks too faint on dry paper, but the plate has been inked up correctly, often the use of moistened paper can rectify the problem. The result is a darker, crisp and clean image with more contrast than it had on dry paper. To wet the paper simply dip each sheet in water then blot off the excess. Many artists use the pronounced differences in printing on wet or dry paper to good creative advantage: printing on dry gives a grainy very lithographic look, printing on wet gives a dense impression almost like an etching.

Tusche, Toxicity, and New Directions for Ink Washes

The great attraction of stone lithography lies in its ability to replicate the repertoire of the medium of drawing, from crayon marks to solid or reticulated ink washes and dry-brush marks. Lithographic solvent-based Tusche is highly toxic because of its tar and Naptha content. The lithographer Nik Semenoff set out in 1984 to find a nontoxic alternative. During his sabbatical year he discovered the use of dissolved photocopier toner as a viable alternative.

The photocopy toner wash method is now widely used in lithography, silkscreen printing, and intaglio. The process is no longer solvent based so artists can enjoy the pleasure of working with grainy washes, solid black brush strokes, and dry brush effects without exposing themselves to noxious fumes. The main precautionary measure required is wearing a dust and particle mask when mixing the toner particles into solution. Best purchase a ready made solution such as Lascaux black wash medium.

The method requires the use of specialist sheets of acetate or transparency, such as 'truegrain film' that allow for wet brush work to register faithfully and without unwanted 'beading'. These reprographic films can be expensive, but materials such as inkjet acetates or slightly sanded sheets of acetate can be used a cheaper alternative. Once the image has been drawn the transparency is exposed to a photo sensitive emulsion, such as a photo-litho plate, a polyester plate (transfer via photocopying), a coated silkscreen, or a photo polymer plate (intaglio type or solar plate).

samples of reticulated wash work using photocopy toner. (left): Donna Adams - wash for intaglio type | (right) wash for waterless lithography by Nik Semenoff.

Four Color Polyester Plate Lithography (CMYK)


Joan Hausrath, four color polyester plate project: final print, set of CMYK plates, detail

The artist Joan Hausrath writes on her four color process: "These plates were made by using Photoshop in CMYK mode. Each plate was printed using Channels for color separation. Registration was easy – I used Photoshop to put registration marks on each plate, positioning them a couple of inches away from the image. Then when I printed the first plate in yellow, I inked the registration marks with black. For the three plates that followed, I did not need to ink the marks, but used them on the plate to match up with the marks already printed on the paper. The translucency of the plates makes it easy to position the plates. I printed the plates with an HP LaserJet. To make sure the carbon adhered to the plate, I ran the plate back through the printer and on a blank Photoshop image so the plate got heated a second time. The paper was Arches 88 printed dry on an etching press – no blankets, but several sheets of newsprint instead. (Dry paper eliminates the expansion factor that can be tricky for registering on damp paper.) The inks were Handschy process colors with a bit of magnesium carbonate mixed into the magenta. (I learned that if I was printing on a hot day, I had to keep the inks cool so I put them in a small ice chest with some ice cubes.) Each color had to be completely dry before the next color was printed so that the ink on the paper would not offset onto the plate. The four color print took four days to print."

 

 

"The halftone screening function of most laser printers is accessed through the OUTPUT and SCREEN button displayed in the PRINT menu. You can either use the printer's default screen, or type in your own preferred dot size, screen angle, and dot shape."

If you examine the dots of ink on the paper with a loupe, you can see that they do not lie on top of each other, but are positioned so they print separately. This is thanks to Photoshop color separation. It is also possible to print multi-color prints (non-color separation) using Pronto Plates by using this same registration system. The colors can be developed on Photoshop using layers, and then registration marks printed on the plates. For non-digital images, use a photocopier to make the plates or draw directly on the plates and then make the marks on the plate by hand using a fine Sharpie pen. Again, the only marks that need to print on the paper are from the first plate. The marks on all subsequent plates are used as guides in positioning.

Creating Polyester Plates using a Digital Photocopier or Laser Printer

Many of the latest generation photocopiers are ideally suited for imaging Pronto Plates. These machines give a dense toner deposit which is automatically heat-fused to the plate surface, so no additional heating is required to give a stable and editionable lithographic plate. The HP A3 sized laser printer (HP 5000) also comes especially recommended for polyester plate lithography as it operates with a higher fuser temperature than some other models, making it ideal for creating stable lithographic printing plates. Despite their thinness, toner-fused polyester plates can be very durable; in industry they are used for print runs of up to 20,000 copies.

HEAT SETTING TIP: Routinely run your plate through the laser printer or copier a second time or more (without an image); the additional fusing run will ensure sufficient heat setting. This is the best way to make lasting plates and to avoid plates breaking up during printing!

Polymetaal supplies the polyester lithographic plates in the following sizes:

  • Polyester Plate Litho, 10 sheets in tube, 33x50cm (13"x20"), art.nr. 021601
  • Polyester Plate Litho, 10 sheets in tube, 60x82cm (24"x32"), art.nr. 021603
  • Polyester Plate Litho, 10 sheets in tube, 82x120cm (32"x47"), art.nr. 021605
  • Polyester Plate Litho, on roll, 82cm x 100 meters. (47"x 328'), art.nr. 021607