polyester plate instructions
Polyester Lithography Plates
These plates were invented by the offset industry as a way to skip photographic color separations and be able to print directly on plates without any processing. They are rolled up much like lithographs but can be printed on the etching or litho press. These plates are difficult to re-use and offer smaller editions, but you can draw directly on them in the middle of the printing process, altering the image as you progress.
You can just draw directly on these plates with sharpie and black ball-point pens or anything with carbon in it. Some india inks have carbon, some don't. Remember that everything prints backwards, avoid getting your greasy paws on the plates, and leave a border for easier roll-up. No processing- just sponge, roll up and print!
Digital Image Printing
1. Scan in digital images at 200 to 300 dpi and manipulate them. If you know that you want images to be larger, make them bigger during the scanning process for maximum quality.
2. All tonal images must be in a half-tone, to simulate tonal gradations with dots.
To create a halftone of your image:
If it is not high contrast enough at this point, you can go to Image>Adjustments>Brightness/Contrast and increase the contrast. You can also add blacks to areas using the brush tool.
Next go to Image>Mode>Bitmap Select Halftone
The machine will first ask you the dpi and just keep it at 200 or 300 (whatever you have it at). Then it will ask for halftone lpi- this should be set at 75.
Take a look at the different types of half-tones to see which one looks best to you.
3. Save your image as a JPEG. The printer will take forever if you save it as any other document. Name your image and store it on your flash drive.
4. Follow posted directions for printing on the HP laserjet in the printmaking digi-lab
Hand Printing Manual or Digital Plates
Ink (litho or etching, preferably not soupy) mixed with 10% miracle gel reducer
Pronto or plastic plate
Black and white original at 75lpi with a halftone
Sharpie markers and ball-point pens for additions
1 tbsb gum arabic in a bowl of water, one empty bowl
a relatively clean litho sponge
1. You can make additions with sharpies or ball-point pens at any time.
2. Wet your slab to adhere you plate to the glass surface
3. Roll up a thin slab of ink- keep it thin to avoid pain and agony
4. Sponge your plate with a thin layer of water
5. Roll it up, repeating this process 4 or 5 times in different directions
6. Move your plate to a clean piece of Plexi and adhere with water.
7. Place several pieces of newsprint on the paper on the plate and print, either on the etching or litho press
8. The image might come up slowly- be patient. Use toothpaste or a mix of sodium bicarbonate and water to clean off fingerprints.
9. As in lithography, be sure that you are printing at high enough pressure to pull ink off the plate each time. Building up ink will cause it to fill in quickly
10. To store or change colors: Run through the press multiple times on newsprint to strip the image. These rarely work twice, so best to just get your edition done the first time.
You can add stuff at any time with sharpie or ball-point
You can cut out or block out parts of the plate. You can also print face down onto a print in the same way we used stencils.
You can print on rice paper and glue stuff into other prints
Anything with carbon works on these plates, litho crayon #5 or tusche washes or India ink with carbon in it.
These plates have some drawbacks.
1. It is best to print it in one shot, as storage or long runs aren't always successful.
2. You might be dealing with a lot of scumming- if so, consider cleaning your slab and adding magnesium carbonate to your ink to tighten it up.
3. It also helps to roll it carefully before printing, with some lightness to pick up excess ink.
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