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Welcome to Technical Talk, a new feature on our website which will be written by our printers and guests. We plan to address technical topics that may be of interest to printers around the world. We have identified several subjects to begin with, but we welcome your questions, comments, and suggestions for topics about which you have questions. We intend to change this page from time to time. For more information on printing on aluminum plates, see our Aluminum Plate Manual.

DEEP ETCH BALL GRAINED LITHO PLATE

NEW DIRECTIONS TO 'DEEP ETCH BALL GRAINED' LITHO PLATE FOR PRINTMAKERS
Dwight Pogue, Mark Zunino, and Edward J. Snyder, Smith College, Northampton, MA © April 1, 2003

It is now possible to print any digital image right from your ink jet printer (Epson 7000, 7600, 9000 etc.) DIRECTLY onto an aluminum deep etch ball grained litho plate.

New drawing may be added to digital images on the plate using traditional litho crayons and washes.

USING A REGULAR DEEP ETCH BALL GRAINED LITHO PLATE:
Use the digital image as a key drawing from which to hand draw over using traditional drawing materials (litho crayons, toner washes, etc). The ink jet ink is inert and will not print. The plate is then etched and processed in the traditional manner.

(A). To use as a 'key'drawing, the image must be lightened by 50% otherwise the ink jet ink will diffuse somewhat when it prints on the plate. Use curves or levels to lighten the darkest blacks down to fifty percent to create more of a 'ghost' image.

(B). NOTE: If using a Direct Litho press, the image is easily reversed or 'flipped' before printing.

USING A POSI-GRAIN DEEP ETCH BALL GRAINED PHOTO POSITIVE PLATE:
No more film positives or negatives. No more vacuum frame. Saves time and money.

Posi-Grain photo plates may be sent through the ink jet printer having the image printed in black ink directly onto the plate. The resulting image is extremely sharp with excellent definition. The plate is then exposed to a light source (no vacuum frame necessary), developed and it is ready to print on a direct litho press. It may be printed as is or new drawing may be added using traditional litho crayons and washes (visit Tamarinds Website and click on Technical Talk regarding Posi-grain plates).

Brief history of this process: Dwight Pogue and Edward Snyder have been working together since 1995 printing out ink jet positives for printmaking students using photo-lithography. Their goal has been to try and get quality results close to the printing industry's expensive image setters while using inexpensive ink jet printers. During one of their moments of frustration, when the ink was not dense enough or the digital image had objectionable wavy lines, Dwight mentioned that direct to plate would be the ideal solution. Problematic film printouts would be eliminated altogether. Then in November, 2002, Ed said "lets try printing a Posi-Grain on the Epson 9000." They did and it worked! The definition was excellent. Mark Zunino exposed the plate to a bright light source and developed it and then Dwight printed it. They then experimented with smooth commercial photo plates but discovered only the Posi-Grain held the finest detail. Ink jet printouts on smooth plates were slightly blurry, whereas the deep etch grain of Posi-Grain holds perfect detail. Dwight and Mark then devised a simple method for registering Direct Plates for multiple runs and four color separations.

Materials required: One or more yellow light bulbs and clip-on 110 volt lamp fixtures. Yellow lights do not expose the Posi-Grain plates and are therefore 'safe' to use in the room where the ink jet printer is located, as well as the darkroom for developing the plates. Natural light from windows and other light sources including fluorescent tubes will expose the photo plates. Until plates are exposed and developed, they are light sensitive.

NOTE: If cutting metal plates to run through the ink jet printer, be sure to carefully file and or sand any rough edges or slightly 'raised' edges - which could potentially damage ink jet heads.

Printing black ink jet onto a ball grained photo plate.
By Edward Snyder

To print a gray scale image onto a ball grained photo plate using an Epson 7000, or 7600 simply print it "as is" directly onto the plate! Feed the plate as you would a single sheet of paper. (For those of you who do not know, the new large format Epson printers feed paper straight through the printer without making any turns, making it possible to print directly onto a metal plate.) Make sure you set the ink button to print black ink (in order to block light), not color ink in the Epson printer dialogue box. I prefer the "Semi Gloss Photo Paper" setting for the "Media Type". The "source space" is left to whatever you are set at, either 1.8 or 2.2 gamma, and set the "Print Space" to "Same as source. Next, in the "mode" section, click> Custom> Advanced to bring up the advanced dialogue box and set the print quality to "Superfine 1440", the "Automatic" in the mode section will be the only choice with the black ink button on.

Print a test of the image on paper using the same settings for evaluation before printing on Plates.

Note: If you prefer or need a darker image, try one of the "Print Space" dot gain settings (farther down the list) from 10% to 30%, the "Dot Gain10%" being the darkest. Finally the other "Media Types" such as "Photo Quality Ink jet Paper", will also provide you with a darker image, but can cause the ink to pool and run. It is best then to adjust your image in the Curves ("Image> Adjust> Curves or Levels) for a lighter or darker image, and then use the "Semi Gloss Photo Paper" setting, (this setting seems to spread the dots apart slightly and prevents ink pooling.)

Printing colors onto a ball grained photo plate.

There are many ways to print a color image, how you plan it is a matter of preference. I personally avoid doing full four color reproduction separations in favor of a more creative hands on processes.
You can plan to print a few color areas or you may want to print colors under a hand drawn black & white keytone image on mylar, by either printing the three colors C,M,Y, of a separation or by using spot colors to color in a black & white image.

No matter what you decide, you will need to covert an RGB image to CMYK (Cyan, Magenta, Yellow, & Black) or work in CMYK initially in order to work with printing ink colors. Before you can print color plates with an Epson Printer, the first thing that must be done before converting to CMYK is that you must select a CMYK profile that works with the Epson random dot pattern, and as the choices given are not compatible with the stochastic style dither dot produced by the Epson driver, you will have to make a custom one. It is difficult to understand or explain how the settings work to do this and I would need to write a chapter in a book in order to do so.

I have tested many different settings over the years and have formulated a recipe for a custom CYMK profile which lends itself well to hand printmaking.

Note: Most CMYK profiles are set up to work with standard halftone rows of symmetrical dots that form patterns that rely on angled screens printed in perfect registration. These are provided for the offset industry and do not apply for fine artist / printmaker. If you use one of these offset screens you will almost always end up making an overall darkened image, best described as a "mud mess". This is caused by the overlapping of the dots.
To avoid all the pitfalls use the custom CMYK formula that I a have developed by years of trial and error. Use this formula freely, but I ask that you to let me reserve the copyright to this information.

Starting with an image in RGB mode or if creating an image in CMYK set the CMYK color settings as follows. (This will not work if you have already started or converted an image to CMYK.)

In Photoshop 6.0 (it is the same in version 7.0, but not 5.5 and under), go down from "EDIT" to bring up the "COLOR SETTINGS" dialogue box. In the working spaces area click on CMYK and scroll up to Custom CMYK. Now in the Custom CMYK dialogue box choose these settings: Ink options area-ink colors- choose SWOP Uncoated and keep dot gain at 25%. Next in the "Separations options area choose "separation type "GCR" button. Then for the "Black Generation" choose "Heavy". Set the total ink limit to 400%, the black ink limit to 80%, and the UCA (under color addition) amount to 100. This puts all the color inks back under the darkest areas. For those of you in the know I use this method in order to adjust the curve to my liking.

Now under EDIT > MODE choose CMYK to convert your image. You are ready to create an image which can print out nicely. Note: the black channel can be lightened or darkened according to your liking.

How you proceed from there is your choice.

Under "Window"> "Show channels" you can see the separate CMYK channels in the dialogue box.
Now you can choose and print each one separately, or create new spot channels under the black channel, even create different opacities for some color channels - especially if you hand color in your CMY under a scanned, hand drawn key drawing. By using some of the CMYK colors along with your chosen spot colors, you can create a more original print.. In addition, you could digitally hand color your image with your own ink set. This would be a new way of creatively hand separating your image.

Once you are satisfied with your image click on the button with the triangle in the channels dialogue box, then choose "split channels". Print each window separately the same as a grayscale image in step one for printing single color images.

Remember, there are many variables to consider, a lot this depends on what paper and ink you use or type of press you are printing on. ONE IMPORTANT TIP TO REMEMBER: If you cut plates into smaller pieces to run through the ink jet printer, file or sand the edges carefully. A jagged edge could damage ink jet heads!

Registering the Direct to Plate image on multiple plates
By Mark Zunino

This process is to be followed if the printmaker wishes to use a punched hole registration system for use on a direct press. However, these directions also include testing, developing and important border burn information crucial to all users of this photolithographic technique.

Since there are no films to pre-register using this process, it is necessary to utilize the computer to set registration tabs (see instructions in computer directions). These tabs are set at equal locations from the image on each plate, and allow for the precise cutting, and eventual punching, of the plates.

The process is as follows:

• Prior to exposing an entire plate, it is advisable to make a series of test strips to assure proper printer ink density, and exposure time.
• Choose an area on the image, which has a wide tonal range, and print it on a thin (3" wide by 6" long) strip of plate.
• Using an opaque sheet of paper (Goldenrod or Ruby-lith type) as a mask, cover all but a 1.5" strip of the plate in the exposing unit, and expose at a low time increment.
• Once first exposure is complete, expose another 1.5" area of the plate to the light and continue to repeat process until all of strip is exposed. Develop the strip, (see instructions below), and use the time setting which gives the closest proximity to the original image.

NOTE: it is advisable to start with longer time increments to set an acceptable range, and to then repeat the process with shorter increments within the optimal range. ALL PLATEMAKERS AND UNITS WILL BE DIFFERENT DEPENDING ON LIGHT AND TIMER TYPE, BUT ONCE TESTS ARE COMPLETE, THEY SHOULD NOT NEED TO BE REPEATED UNLESS THE IMAGE TYPE CHANGES.

-Once exposure times are determined, the entire image/plate may be exposed and developed.

-To develop plate, place in a sink or developing tray large enough to accommodate the plate flat. Pour enough developer on a rag or cotton pad, (over the plate is okay), to fully saturate it, and distribute over the entire surface of the plate. Continue to rub the plate surface and you will notice the emulsion being removed as the developer is redistributed. Pay special attention to the images as well as the borders, making sure no area is left undeveloped.

NOTE: Make sure to fully develop areas where register tabs where printed to expose them and make them as visible as possible.

-Once developing is complete, (You may need to add additional amounts of fresh developer as you rub plate), rinse front and back of plate, squeegee and dry completely.

-Place plate on flat surface, and lay ruler across bottom edge, according to tab marks. Score plate with sharp utility knife, and bend at score to cut plate.

NOTE: Before continuing this process, it is vital to explain the need for a plate hole puncher, and registration pins. In the past, we have used common, and various professional plate hole punches, but have found that those holes often don't fit the pins we use. Since the holes and pins are utilized throughout the digital/photographic process, (from films, to plate exposure, to paper, to printing), it is imperative that the system you employ is consistent. Professional registration systems, such as the one sold by Takach Press Corporation, are a worthwhile investment, and will definitely resolve your plate punching issues.

-Place plate in hole puncher careful to line up center mark on plate with center mark on hole puncher, and punch plate.

-At this point you may rub the plate up with plate finisher/cleaner, and print it, or give it an additional border burn to fully clean the edges, and create an absolutely perfect edge on each plate.

-For the border burn, you need to cut a piece of 100% opaque paper (like Goldenrod or Ruby-Lith film), .25" smaller than your original image in both directions. Take one of your developed plates, center the opaque mask over the image and lead two strips of punched clear acetate to two punched holes on the plate. Line up holes, and place pins through holes. Tape acetate strips to back of mask making sure there are no buckles on mask or strips. This one mask will be burned on each of the plates you use for this image making the borders consistent from plate to plate.

NOTE: Make sure all lining up is done in a safe light environment, as any exposure of the already developed image to light will cause a loss of that image during subsequent developing. Additionally, the border burn can be done for any photo-litho process to yield a clean, straight border area.

-Place the mask over the image using the register pins, and expose the plate to light for a long time. Develop the plate as above, using as little developer as is necessary to fully clean the borders. It is okay to get developer in the image area during this developing stage.

-Rinse the plate and squeegee excess water. Leaving the remaining water film on the plate pour Gum Arabic and distribute with a clean Gum sponge. Thin the gum film with the sponge and fan dry. The plate may then be printed or stored in a dry dark place.

-Before printing it is important to remember to wash off the gum film, dry the plate and then rub it with plate finisher/cleaner. Fan dry and let it sit for a few minutes, wash off and then print as a regular ball-grained plate.

ADDITIONAL NOTES:

• You can use the hole punch registration system on the direct litho press by placing register pins on the press bed, (DO NOT LAY ON TYMPAN OR LOWER SCRAPER BAR ON PINS FOR THEY WILL LEAVE IMPRESSIONS ON EITHER SURFACES), and punching holes in your calendared printing paper.
• You can use register needles or T and bar registration techniques with any of these processes, as you would any litho plate.
• Use the additional possibilities offered by the Posi-Grain plates such as the Triple-Burn (see Tamarind's Technical Talk web site at http://tamarind.unm.edu/techtalk.html), and the hand drawing (emulsion into lacquer base) options in combination with the computer.

All material copyrighted February 2003 by Dwight Pogue, Mark Zunino and Edward J. Snyder, Smith College, Northampton, Massachusetts. For further information, contact:

Dwight Pogue
Art Department
Smith College
Dpogue@smith.edu

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For the first time, a high quality positive photo emulsion coating on a conventional deep etch ball grained plate is being produced specifically for printmakers using direct litho presses. Posi-Grain plates are manufactured by Precision Ballgraining Corporation and were developed in collaboration with Dwight Pogue and Mark Zunino, printmakers at Smith College, Northampton, Massachusetts.

• Uses:
  
• To expose graphite and wash drawings made on mylar as well as halftone films and computer-generated "dither" random dot patterns on clear films.
• To add hand drawn imagery to a photo plate that has already been exposed and developed. The plate is then processed and rolled up like a regular ball-grained plate. The process is capable of retaining minute detail.
• To produce reduction exposures. A single Posi-Grain plate can easily be exposed and printed multiple times in a reduction manner, permitting two or more images/colors to be printed from one plate.
• To transfer a 'key' outline or ghost drawing/image to multiple plates - one for each color - which can then be hand-drawn using traditional lithographic drawing materials.

History of Posi-Grain Plates
Dwight Pogue © December 30, 2000

I first began making lithographs using photo plates (wipe-on negative emulsion on ball grained plates) in 1970. I was encouraged when one of the prints was accepted to Graphics 71, a national print exhibition in Silver City, New Mexico. By 1974, I was making four-color separation prints, one of which was in the l976 Fifth British International Print Biennale. At that time I was using Hawson Algraphy "Olympic Gold" positive working plates. However, by the late seventies, I was back to hand drawing on uncoated deep etch ball grained plates, using an average of eight or more plates for an edition of lithographs. Occasionally, I included one or two positive plates for quick areas of color.

I always felt the ideal plate for artists/printmakers would be a positive coated deep etch ball grained plate because hand drawing could be added after development and it would be easier to print using a direct lithographic press. In 1994, I introduced a two-week computer component to my traditional lithography courses. Students were exposing random dither dot images onto smooth, commercial positive photo plates. I was not happy with the results and soon became interested in finding a way to combine hand drawing with computer images on the same plate. Since it is easy to add new hand drawing to deep etch ball grained plates and to print them on direct litho presses, the solution was to develop a high quality positive photo emulsion coating that could be applied to a conventional deep etch ball grained plate. When the opportunity to develop such a plate finally arrived, thanks to Jim and Michael Hogan of Precision Ballgraining Corporation, I asked my colleague, Mark Zunino, and Jim and Michael to join me in conducting research to perfect it. What I guessed might take three months to accomplish took almost three years. In the spring of 1997, Michael produced several six-inch square samples for trial. Mark and I began making tests. Then the four of us experimented with different emulsions and different methods of coating plates to achieve optimum exposure times for delicate washes and drawings. Refinements were made over a period of months, and further trials eventually led to better-than-expected results.

Together with Precision Ball Graining Corporation, we introduced Posi-Grain plates for the first time at the March 1999 Southern Graphics Council Conference in Tempe, Arizona. After researching Posi-Grain's capability for multiple reduction exposures/printing, Mark and I conducted a demonstration at Tamarind Institute, Albuquerque, New Mexico, in April 2000.

How to Use Posi-Grain Plates
Dwight Pogue, ©March 2000

HANDLING: Prior to and during exposure and development, handle the plates in yellow light. A yellow incandescent 'bug' light or yellow plastic sleeves that slip over fluorescent tubes will protect the plates from being exposed.

EXPOSURE UNIT: Although it is possible to construct a workable plate exposure unit with a light source, sheet of glass and a pad of foam rubber, it is not recommended if you want to achieve high quality results. It is often possible to locate a good used plate-maker such as a flip top Nu-Arc brand. Plate-makers should have a suitable light source and tight vacuum glass frame capable of producing approximately 20 pounds (sq. inch) or more of pressure. The "sensitizers" used in positive photo emulsion coatings have a range of 350-420 NanoMeters. Therefore, the ideal light source is a metal halide diazo bulb. Another bulb that will work is a pulse zenon diazo bulb. The zenon however, does not produce as even a light as does the metal halide bulb. Check the plate-maker to determine the type of bulb it uses.

EXPOSING THE IMAGE:
To determine the optimum exposure for your unit, use either the free test strip provided in each package of plates, or cut several two-by-ten-inch test strips of plate from a full Posi-Grain plate and expose them for different lengths of time. During the early stages of researching these plates, one of our criteria was to provide an emulsion which would allow a wider range of acceptable exposure times than most commercial photo plates. Posi-Grain plates are therefore able to hold a wider range of delicate articulated washes and generally require longer exposures than commercial positive plates.

Unless bleeding the image off the plate, I always "double burn" plates in order to obtain perfectly clean border/non-image areas. This is particularly desirable when exposing images on multiple plates such as four-color separations. The double burn will create a perfect image edge regardless of how many colors are printed because the same single border mask is used for all the exposures. The key to successful double burns is to align everything to the same two pins on your registration system.

Once you have multiple images perfectly registered on each plate, it is easier to set up a "T" registration system on your direct press.

DEVELOPING:
To develop the strips and, ultimately, the full-sized plates, use a soft (photo type) sponge and rubber gloves, moving the PG-Developer rapidly in a circular motion (light pressure) repeatedly over the entire plate. Add fresh developer if necessary. (I prefer putting developer on twice - each time thoroughly rubbing it lightly but rapidly). Rinse plate thoroughly with cool water. The plate may then be rolled up in ink and printed, rolled up in ink and counteretched for adding new drawing, or it may be simply gummed and stored without rolling up. If for any reason the plate image should not receive ink readily, simply pour a small pool of PG-Cleaner on it and rub with cotton until dry. Wash off with water and roll up. For storage after developing, we recommend that you remove the excess water from the plate with a gum sponge, then gum the plate with regular 14 degree baum gum arabic (we recommend GA-100). Buff lightly with cheesecloth - not a tight buff as for non-photo plates. Store the plate in a dark, cool area. Remember to keep the plate covered with black paper when in the open (I place a sheet of black paper over the plate even at the press when I'm not actually printing).

PRINTING THE IMAGE:
Rinse plate with clean water, remove excess and roll up. If the image should not receive ink readily, simply clean it with PG-Cleaner. As a matter of course, I prefer pouring a small pool of PG-C on the image and rubbing it with cotton to remove the old gum and thus clean the plate. Buff lightly with fresh cotton and fan with a hand fan. The plate is now ready to be washed with fresh, cool water, rolled up and printed.

ADDING NEW DRAWING: If you want to add new drawing to the developed image, roll the image up using black ink such as Daniel Smith Velvet, Classic Black, or Senefelder's Crayon Black. Use either a leather or composition roller. When fully inked, remove any roller marks, tint or scum using a Scrunge sponge (foam rubber). Apply a counteretch solution, wiping it with cotton carefully and lightly. Immediately rinse with water, remove the excess with a sponge, apply more counteretch and repeat the process. After two or three counteretch applications, rinse the plate with water and blot carefully, then fan dry immediately.

The plate is now ready for new work. Although all litho pencils work well, we prefer Stones Crayons. Counter Etch Solutions: (either works well) (1). One gallon of water, one ounce of Phosphoric Acid and one ounce of Hydrochloric Acid. (2). One quarter teaspoon of Anhydrous Citric Acid crystals to ten ounces of water.

ADDING WASHES TO A ROLLED UP IMAGE:
Tusche washes made with water rather than solvent-based washes are recommended since some solvents can alter or dissolve the photo emulsion. Toner washes may be used if made with distilled water and small amounts of Photo-Flo or liquid soap.
The Art Department at Arizona State University (Tempe) uses a Ricoh Toner type recipe which works very well:
1 teaspoon of Ricoh Toner type 6080,
2 ounces of distilled water and 10 drops of Photo-Flo.

Once dry, toner washes must be 'set' or attached to the plate prior to applying the first gum etch. One ideal method for setting the toner wash is to allow only the vapors of the naptha to reach the plate. Construct a simple lightweight plywood lid and place several inches of cotton in it. Fit a wire screen over the cotton to secure it to the inside of the lid or box.

To avoid breathing toxic fumes, do the following process outdoors or use a ventilated hood.

Using rubber gloves, pour naptha (white gas) onto the cotton. Immediately place the plate face down (with the image directly over the cotton) on the lid and allow the vapor to 'set' the toner washes. If preferred, the lid may be placed over the plate as the vapors will still set the toner. Test to ensure that the toner wash is attached to the plate by lightly touching a small area of the wash. If the toner comes off, it needs another application of naptha fumes.

After new work is added, process the plate as you would any regular ball grained litho plate: talc, gum and buff tightly. Take plate to a well ventilated hood area and wash out the image thoroughly with lithotine and then lacquer thinner (wearing gloves of course). Glaze cleaner may be used as a final wipe to super clean the plate, however it is not necessary in most instances. Apply red lacquer V with cotton and then buff rapidly with a fresh, dry cotton pad. Dry with a hair dryer on hot heat for 3 minutes. Apply asphaltum and store or roll up and second etch.

To roll up, wash the plate with water and roll up with black ink and a leather roller. Once fully inked, clean any roller marks and tints with a scrunge sponge or foam rubber and dry the plate. Any small, isolated unwanted spots in the borders may be removed with lacquer thinner and cotton in a well-ventilated area, or with Image Remover and a brush. Talc, gum and buff. Generally, I prefer straight gum for the first etch (after adding the new drawing) and tannic gum for the second etch (after rolling up in ink).

PRINTING:
Printing the Posi-Grain on a direct litho press is the same as printing any medium ball grained lithography plate. Tamarind Institute recently published (1999) a manual on printing ball grained plates on direct presses. It may be ordered from their web site, www.unm.edu/~tamarind.

Emulsion Reduction Process
During October of 1999, Mark Zunino and I discovered that a Posi-Grain plate could easily be exposed and printed multiple times in a reduction manner. This opens up new ways of working for the artist-printmaker by allowing two or more images to be printed in different colors from the same plate. The only condition is that exposure of the plate to bright light during handling and printing must be limited. We keep the plate covered with a black sheet of opaque paper until washing out and rolling up in ink. When rolling up and printing, it is advisable to work in somewhat subdued light. The plates are not sensitive to yellow light, therefore yellow ' bug' lights or yellow sleeves placed over fluorescent lights are ideal when using this plate.

Working Procedure
Mark Zunino, ©March 2001

As long as emulsion is still present on the Posi-Grain plate, it may be re-exposed and re-printed multiple times. A good analogy is reduction relief printing, in which the first state involves cutting out only the whites and printing the rest of the block in a pale/transparent color. Each successive state is printed gradually darker, and later cuts reveal the lighter colors that were printed previously. The emulsion of a Posi-Grain plate acts as the relief surface, and may be gradually reduced and printed between exposures. New imagery will appear only where there is still emulsion, so artists must adjust their imagery accordingly. It is possible to print five colors from one plate, and registration issues are simplified since the drawings for each state are registered before exposure.

There are many variations, but the following may be used as a guide for this process. ·

Make the images on clear acetate, or frosted mylar sheets. Although any opaque drawing material can be used, we prefer Xerox Toner 6R84 mixed with Ethyl Alcohol, and Future Floor Wax, or Ruby Lith for flats (more floor wax will result in flatter washes, more alcohol will result in more reticulated washes). The floor wax serves to fix the toner to the mylar. Note on exposure times: if the light source on your exposure unit is strong, it is possible to overexpose the plate during multiple exposures. Therefore, underexpose the initial states that are printed in light ink, then expose later states at desired length. It may also be necessary to cut the developer in half with water in order to avoid over development.

For the first drawing, make a dense, almost flat black image leaving the desired white areas open. Using registration pins and a hole punched plate to line up the image, expose the Posi-Grain plate following the instructions given, and print the image in light ink. Be sure to keep the plate covered, or in as dark an environment as possible, until ink is applied to the plate; otherwise, the emulsion will continue to expose and the plate will not be able to accept additional exposures. ·

To register the second and subsequent images, hole punch mylars in relation to the first mylar. Use opaque drawing materials such as graphite, Xerox toner washes, etc, to create drawings that gradually become lighter and more open. Print these states in gradually darker values.

Note: new imagery will appear only where emulsion still remains.

An advantage of working with mylar and the hole punch registration system is that you can use a light table to help register the different states of the image. · Once the emulsion is completely removed, or at any time during the production of the print, the Posi-Grain plate can be changed from an emulsion-based plate to a lacquer-based plate, counteretched, and drawn into to use for additive, subsequent states.

Duotone Variation on Emulsion Reduction Technique
For a richer single image involving a wide variety of grays and tonal variations use one plate to create a duo-tone print. For the first state, underexpose the image and print it in transparent black ink. This will ensure that all light values will be present. Once printed, put the positive image on the same plate and overexpose it until only the darkest values remain; print it in a darker version of the first black. This process works well with graphite, computer imagery, and washes. It may be necessary to try several different test strips to achieve the optimum exposure time for each state.

For further information or technical assistance, contact
Dwight W. Pogue
Art Department, Smith College,
Northampton, Massachusetts, 0l063
or Dpogue@smith.edu

Posi-Grain plates and Developer may be ordered from:
CS Pogue Graphics
215 Linseed Road
Hatfield, Ma. 0l088 Ph: (413) 247-9221
Fax: (413) 247-9899
cspogue@mediaone.net

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The following article on printing bases for aluminum plate lithography was written by Ernestine White. Ernestine participated in Tamarind's Master Printer program and has been certified as a Tamarind Master Printer since the end of her internship in May 2001.

The introduction of the offset press and aluminum plates to commercial printing resulted from the need to create printed matter at a faster pace. The offset machine replaced the hand-operated press that once printed images from stone. With materials from the offset industry readily available, the quality of printing from plates in hand lithography has greatly improved. This article addresses the effectiveness and safety of lacquer and shellac as printing bases in hand lithography. Lacquer and shellac are the two most commonly used printing bases today. In the past, products such as Titan vinyl lacquer and Blue C Lacquer were used frequently despite their highly toxic nature. The somewhat less toxic Lacquer V (made by Hanco) is today's printing base of choice, although it dries slower and is less durable than the others and is more toxic than the alternative materials described below.

A decade ago, Tamarind's former education director, Jeffrey Sippel, refined a shellac alternative to the widely used lacquer base. While teaching in Poland, he noticed that printers there were using shellac as a printing base. The problems they encountered seemed to be related more to the application of the material than to the material itself. The uneven film, caused by the rapid drying of the shellac, compromised the quality of the image and edition. Jeff's previous experiments with oil paint as a printing base had been problematic because the oil paint dried too slowly. His solution was to combine materials-1/3 shellac (make sure it is high quality shellac, one that has no water in the contents), 1/3 oil-based enamel, and 1/3 mineral spirits--to come up with a solution that worked well. In fact, Tamarind printers still use it today.

The advantages of shellac are:
1) vapors are less toxic;
2) acetone (used to wash out shellac) is safer than Hancolite (used to remove lacquer);
3) shellac is more easily removed from the matrix, which helps to prevent the image from "filling in" or from getting darker during the roll-up of an image.

The disadvantages of shellac are:
1) if an image in a shellac printing base is not baked long enough, it is susceptible to "water burn" or "dropping out" (gradual fading of image);
2) the shelf life of shellac is short (only a few months);
3) pre-made shellac separates if not thoroughly mixed and must be stirred well before use.

The advantages of lacquer are:
1) once lacquer is cured (we use a hairdryer), the printing base creates a film that is resistant to problems associated with shellac;
2) the image is more durable;
3) it dries quickly;
4) shelf life is many years.

The disadvantages of lacquer are:
1) it can irritate skin and mucous membrane, and can cause headaches and fatigue;
2) long-term use can be harmful to the respiratory system. The use of a respiratory mask or proper ventilation may alleviate these effects to some degree.

More and more printers prefer to use safer materials, especially in classroom settings. The shellac mixture may be the best alternative, although the curing method could be problematic for many facilities because it is ideal to use an oven for curing the image. Alternatives to baking the plate in a special oven are discussed below.

Shellac method as used at Tamarind
1) Mix base in the following proportions: 1/3 shellac*, 1/3 oil-based enamel, 1/3 mineral spirits.
2) Etch image, let rest for a minimum of 1 hour. Wash out image first with lithotine, then with acetone. The acetone will remove any residual drawing materials still left on the plate.
3) Stir shellac mixture well, then apply with a clean rag.
4) Buff well with a clean rag.
5) Heat in a custom made oven at 250 degrees for 10-15 minutes. Shorter heating time can cause problems during proofing and/or editioning. Heating the shellac causes the printing base to adhere better to the surface of the plate and thus creates a stronger and more stable film that cannot be dissolved with lithotine or isopar.
6) Remove plate carefully (it's hot!).
7) Apply asphaltum and buff. Roll up as usual.

The following methods do not require an oven.

A. Buffing shellac mixture
1) Etch drawing, let rest for miminum of one hour.
2) Apply a new gum mask to the image, wash out with lithotine and then acetone.
3) Buff in a small amount of the shellac mixture (1/3 shellac, 1/3 oil-based enamel paint, 1/3 mineral spirits) well, until no traces of shellac are visible on a clean rag.
4) Fan the plate dry for two minutes.
5) Buff in alphaltum, wash out with water, and then roll up with black ink.
*The plate was stored for a few days and then printed in an edition of fifty impressions. There was a visible change--a lightening of the crayon drawn areas--after 35 impressions The tusche washes (Stones paste tusche), remained consistent throughout the edition.

B. Elimination of mineral spirits from mixture
1) Follow steps 1 and 2 above
2) Mix thoroughly: 1 part shellac (use good quality clear shellac) and 1 part oil paint enamel; stir well.
3) Apply the mixture immediately and buff into the plate. Rapid drying causes an uneven film on the plate, so be sure that the entire image is coated.
4) Fan the plate dry for two minutes. Buff in asphaltum, and then roll the plate up in black ink.
5) Wash off the asphaltum with water; there should be no visible sign of the red oil based enamel pigment.
*The crayon and the tusche drawn areas printed consistently. There was no visible change in the edition of 50 impressions.

C: Use of clear shellac only
1) Apply shellac quickly and evenly. It will dry as soon as it touches the plate, which makes it difficult to apply an even film. The plate will show a very slight color change where the shellac has been applied.
2) Process the plate as indicated above.
*There was a slight change (gradual lightening) of the darkest areas, but the changes were not as dramatic as those with the shellac mixture in A. The tusche washes printed consistently.

Conclusion
The mixtures used in B (1 part shellac to 1 part oil-based enamel) and C (clear shellac) above are fairly reliable and stable for editioning. Since the average edition size in a university setting is normally under 25 impressions, any of these shellac combinations should be satisfactory printing bases for aluminum plate lithography. It is difficult to say which is better, although for printing long editions Hanco's Lacquer V is more durable and reliable. Safety is an important consideration in choosing materials.

We welcome your questions and comments: tamarind@unm.edu
All contents ©1998 Tamarind Institute All rights reserved.
Last updated: 11/6/08