Redo with Aquatint

This evening, I made a second plate using an aquatint screen. The second plate has more subtle texture and variation in the line widths and does not produce lines with open bite.

Here’s the second plate. This plate was exposed first with an aquatint screen and then a second time with the artwork. In this plate, the lines are made up of microscopic pits, instead of open grooves.

The plate with aquatint shows more subtle variation in the line widths.

For comparision, here is the original artwork, the print from the aquatint plate, and the print from the first plate.

This is the artwork that I used for the plate exposure. My goal is for the prints to match the original artwork as closely as possible.

The second plate makes use of aquatint. Here there is a greater variation in line width and all lines print without open bite.

This print is from the first plate. That plate didn’t use aquatint and may have been over-etched, resulting in open bite and thicker lines.

Starting a New Print

I just made an intaglio print based on one of my favorite line drawings. The original charcoal drawing is from my time in Geoff Flack’s Foundation Figure Drawing course back in 2010. I made the plate last night from a piece of SolarPlate. The results were decent for a first attempt, but I think in the end I failed to capture the subtlety of the line drawing. My next attempt will be an aquatint, which hopefully will more accurately reproduce the softness in the charcoal lines.

This photopolymer plate works like a classical etching in copper, where the grooves hold the ink and the smooth surface is wiped clean. I’m concerned that I will get open bite in the shoulder area because the lines are too wide. Open bite happens when the groove is so wide that the capillary forces in the ink are unable to hold the ink in place as the plate is wiped. I’m still investigating why the lines in the shoulder are so thick. It could be the original artwork, or I may have over developed the plate.

The first step in printing intaglio is to apply ink to the plate. I like to use a scrap of cardstock to help push the ink into all of the grooves.

Here I’m starting to wipe the plate with a piece of tarlatan (basically a piece of cheesecloth that has been heavily starched). The goal for this pass is to remove the heaviest ink deposits while grinding the ink into the lines.

After removing the bulk of the ink with the tarlatan, I switch to newsprint which removes surface ink while leaving the lines. The newsprint also tends to polish the smoother parts of the plate.

At this point, I’ve wiped with tarlatan, then newsprint. All that remains is to clean up any ink that has stuck to the edges of the plate.

Here’s a close up of the plate immediately before printing. I’m a bit concerned that the fingernails are holding too much ink.

Here’s the first print, on a scrap of damp Rising Stonehenge. As I suspected, there is some open bite in the lines of the shoulder, and the lines in the fingers are not as subtle as the original artwork. The grey rectangle is called plate tone and is created by the residual ink on the plate. Plate tone is one of the hallmarks of the intaglio process. In this test print, I over-wiped the bottom of the plate, leading to uneven plate tone.

Epson 3880 Roller Problems

“Theory and practice are the same, in theory, but different in practice.”

My first attempt at eliminating track marks on my ImagOn emulsion was to make a window mat carrier, the theory being that the rollers on the border of the window would lift the center rollers above the surface of the ImagOn.

My plan was to make a window mat carrier that would lift the top rollers above the surface of the ImagOn in order to avoid track marks.

I tried a bunch of different window mat carriers and found they either had no impact on the track marks or they got hung up on the top edge of the window mat. A quick look inside the printer and a perusal of the service manual showed me the problem (see page 53 and section 5.3.17).

The top side of the Epson 3800 paper feeder has 8 roller assemblies, each 2″ wide and holding two small rubber rollers. The rollers are organized into an assembly called the grid roller. The paper passes from back to front under the grid roller on the way to the print head. The grid roller presses the paper against a steel paper feed roller that actually pulls the paper forward.

Each roller assembly is free to move up and down independent of its neighbors. A metal spring clip holds the roller assembly firmly against the paper.

Because the roller assemblies can move independently, the ones inside the window will roll across the surface of the plate. This roller is partially inside the window mat with the top edge riding on the edge of the mat.

In practice, the rollers fall into the window in the mat and run across the surface of the emulsion, leaving track marks.

Once I had a good understanding, I tried a couple of ideas without success:

  • Ran a printer cleaning sheet in case dust or goop on the rollers was responsible for the marks.
  • Attempted to reduce the pressure on the rollers by increasing the paper thickness setting. My hope was that this setting would prevent the Paper Guide Upper Assembly (see page 53 in the service manual) from pressing down quite as hard.
  • Attempted to reduce the pressure on the rollers by setting the paper type to glossy. My hope was that the printer might use less pressure when printing on glossy.
  • Tried printing on a very thin plate consisting of ImagOn laminated to a piece of Pictorico OHP transparency film. This plate was thin enough to run through the sheet feeder. My hope was that the Paper Upper Guide Assembly might not be able to exert as much pressure on really thin media.

I’ve considered, but not tried the following ideas

  • Somehow pull the middle 6 roller assemblies up against their spring clips so that they can’t touch the emulsion. This would leave the 2 roller assemblies on the end to move the plate. I don’t plan to try this because it might void my warranty and because the rollers are probably necessary to keep the media flat as it goes under the print head.
  • Make the ImagOn surface more resistant to scuffing by removing the protective plastic and letting the plate dry, exposed to air before printing.
  • Make the ImagOn surface more resistant to scratching by heating the plate. Not sure if heating the plate will harden or soften the emulsion.
  • Make the ImagOn surface more resistant to scratching by cooling or even freezing the plate. This approach may have problems with condensation.
  • Make the ImagOn surface more resistant to scratching by pre-treating it with vinegar. I don’t know whether the plate is still light sensitive after being treated with vinegar.

As you can see, I’m pretty close to being out of ideas. It is possible that ImagOn DTP only works with high end printers like the 4900, 7890, 7900, 9890, 9800, and 9900 that use vacuum suction to hold the paper in place without touching the top surface.

It is also possible that my 3880 is defective and pressing down too hard. I will know tomorrow whether my printer is defective. If it is not, I may have to give up on DTP and make a strategic retreat to single exposure ImagOn. This means I will need a vacuum frame, but I won’t need a calibrated light source.


Mostly depressing with a ray of hope

Tonight’s experiments were depressing, although there may have been a ray of hope at the end – I won’t know until tomorrow when I expose and develop the plate I printed this evening.

It seems the problem is that the Epson 3880 front feeder, which is the only print path on the 3880 that can handle thick stock like 0.030 polycarbonate plates, uses a tractor feed mechanism with rollers on the top side of the media. When using softer media, like photopolymer emulsion, these rollers tend to dig in and leave marks that look like bulldozer tracks. A brief search of digital photography forums on the internet found that other users have encountered this problem when using gelatin surface papers that replicate the look and feel of real darkroom paper. No one had a solution other than switching papers or switching printers. It seems that the higher end Epson printers like the 4880 and the 9800 use a vacuum system to hold the bottom of the paper in order to eliminate rollers that could make contact with the top surface of the paper. I’m still hoping I can find a work around because I really don’t want to be faced with the choice of abandoning ImagOn DTP or upgrading my printer.

I spent the evening trying out various carrier designs, hoping to find something that would lift the middle drive wheels off of the emulsion. My hope was that a window-mat design would cause the entire drive system to ride at the height of the mat. I found that carriers with thicker window mats would tend to jam as the drive wheels exited the window cutout. This suggests that the drive wheels can descend independently into the window.

In the end, I found that a three-sided window mat, which was open on the bottom would pass through the printer without jamming. I printed a plate with this carrier and found that it still shows the track marks, but they may be less severe than my previous plates that protruded above the top of the carrier. I won’t know for sure until I expose and develop the plate tomorrow.

Cross your fingers.

Just loading a piece of paper into the front feeder is enough to get tractor marks. In this image you can see a piece of 2-ply Bristol Vellum that was run through the front feeder on my Epson 3880. Note the diagonal groove running from the lower right corner to the upper middle. The printer makes these grooves, even if I load and then unload the paper without printing.

In an attempt to prevent the top drive wheels from touching the plate, I made a carrier with a piece of 4-ply mat board on top of a thin piece of Bristol Vellum. I could never get this carrier to load. It would always jam when the top rollers hit the edge of the mat board after traversing the inside of the window. You can see the dents and gouges caused by the rollers grinding into the edge of the window.

Here’s another view of the gouges. The interesting thing is that a window mat with no backing paper never jams, but the window mat with backing paper always jams. I also tried running the carrier with the piece I had cut from the window inserted back into its hole and it ran fine.

I was finally able to prevent jamming by making a carrier that is open on the bottom. Since the carrier doesn’t have an edge on the bottom of the window, the drive wheels don’t get stuck.

Here’s the plate I printed tonight with the new three-sided carrier. You can still see the tractor marks running vertically in the image, below the number 26.

The marks are more prominent in the darker parts of the plate, but at this point they seem less severe than the marks on my previous plates which protruded above the top of the carrier.

Here’s another angle of the same tractor marks. I need to let this plate dry overnight before exposing and developing, so I won’t know for another day whether I have reduced the marking to an acceptable level.

Good news, bad news

The good news is that I am not actually getting head strikes when printing directly to ImagOn plates. The bad news is that the top surface drive wheels on my Epson 3880 printer are leaving tracks in the ImagOn emulsion.

The photo below shows the problem. The worst wheel marks pass through the entire length of the plate, hitting steps 95-97 at the bottom all the way up through steps 5-7 at the top. The drive wheels also put enough sheer force on the emulsion to cause curved wrinkles like the one that passes through the center of step 75. Less severe tracks marks also appear on left and right sides of the plate.

I was hoping these drive marks wouldn’t impact the quality of the matrix, but as with fingerprints, the marks seem to prevent the ink from adhering. Here’s a close up of the narrow track mark on the right side of the plate.

Here’s another close up of the big track mark in the center of the plate:

The impact of these track marks is unacceptable, so hopefully I can find a solution.

When I first saw the marks, I erroneously concluded that they were due to printer head strikes, and I was able to eliminate them by creating a carrier where the surface of the ImagOn was recessed below the surface of the surrounding window mat. It seems the reason the recessed carrier eliminated the marks is that it prevented the drive wheels from touching the recessed emulsion. The problem with the recessed carrier was that it was too thick to reliably pass through the printer’s front slot.

For the plate in this post, I modified the original carrier design in such a way that the plate was no longer recessed, but the carrier was only about 1mm thick. My hope was to make a carrier that was thin enough to feed reliably, and then use the “Widest” setting for the platen gap to eliminate what I thought were head strikes.

With this larger plate from the new carrier, it is now abundantly clear that the banding I’ve been seeing is due to contact with the drive wheels and not head strikes. I now have a few ideas about why I am getting track marks:

  1. It is possible that the ImagOn emulsion is so delicate that any contact between the drive wheels and the top of the plate will cause tracks. If this is the case, a thinner, recessed carrier may work, but I may have problems scaling it up to larger sizes because I will always need to leave enough border in the window mat so that there are enough drive wheels in contact with the mat to actually move the carrier through the printer. I might find that my 17″ wide print path needs a 3″ margin on either side, thus reducing my maximum plate width to 11″. If the ImagOn emulsion is really that delicate, one obvious question is how are others successfully doing ImagOn DTP? One thought is that they may be using a different model Epson printer. Some of the higher end printers, like the 4880, use a vacuum suction system so that there is no contact with the top of the print.
  2. I may have the paper thickness setting incorrect, causing the drive wheels to clamp down much harder than is necessary to move the carrier. Increasing the paper thickness setting might reduce the pressure enough to eliminate the track marks or reduce them to an acceptable level. My evidence for this theory is the wrinkles in the ImagOn. I know from trying to peel ImagOn off of a plate that the emulsion adheres pretty well, meaning that printer would have to generate enormous forces to cause the wrinkles. I don’t think I could make similar wrinkles on a dry plate with my fingernails.
  3. The design of my carrier, which allows the plate to protrude above the level of the window mat, may be causing the entire force of the drive wheels to hit the emulsion. Perhaps a carrier that put the top surface of the plate flush with the window would divert enough of the pressure to the window mat to reduce or eliminate the track marks.

Now I have another set of experiments ahead of me . . .

QTR Calibration

While sorting out my ImagOn plate carrier design, I have been working on calibrating QuadToneRIP for printing directly to ImagOn.

My earlier experiments were based on a custom curve that used only black ink. This initial curve was very basic, adjusting only the Ink Setup. I made no changes to the Gray Curve, Toner Curve , Toner Curve 2, and Linearization tabs.

When printing I used the following settings:

  • Source: Manual Front
  • Type: Matte Paper
  • Curve 1: Black-50-100-100-100 (my .qidf file from above)
  • Resolution: 1440 Super
  • Speed: Uni-directional
  • Black Ink: Matte Ink

With these settings, I was able to print decent gradients, but I knew that my darkest steps were too dense. My plan for calibrating QTR is to first determine a Default Ink Limit value that will dither black portions of the image to the lowest dot density that yields a solid black in final the intaglio print. With this value nailed, I can then print out a step wedge to help me linearize the output.

The picture below shows an unexposed plate that has just been printed with a 100-step wedge. The colors are skewed because the photo was taken under weak incandescent light to avoid exposing the plate. Clearly steps above 70 have too much ink. There is so much ink, in fact, that the individual dots are pooling together. Steps up to 60 look pretty good, and I would need greater magnification to judge the steps between 60 and 70. Even if these steps are well printed, they may still be too dense to prevent an open bite.

This experiment may look like a failure, but it is actually a success. Once I print this plate, I will be able to determine the first step that gives me solid black in the intaglio print and then I will use this knowledge to set a Default Ink Limit so that the darkest portions of the image never generate a dither pattern denser than the ideal first black step.

Scaling up

I’ve found time and again with printmaking that mastering a process at small scale is only half the battle. Scaling up alway brings new challenges. For example

  • Hand printing to etching press. I was making great linoleum block prints with a baren and then I tried it in the etching press and found I was back to square one because I didn’t know that I needed a stiff material between the rollers and the plate.
  • SolarPlate Relief Prints from 4″x5″ to 8″x10″. In the small scale, I was able to use stencils made from gouache on vellum. I found that the moisture in the gouache made vellum wrinkle too much at the larger scale and this prevented me from getting crisp edges during exposure. I eventually moved to paper stencils glued to glass.
  • Relief Prints from 8″x10″ to 24″x30″. It turns out it takes a lot longer to ink a complex design that is 30″ long. If you use water-based ink, it may dry before you are done inking, so an oil-based ink like Akua Intaglio is easier to use in the larger sizes. Small prints can be easily dried by pressing them. Large prints are harder. If you press them and don’t have some sort of forced air blower it may take a long time for all the moisture to wick away from the center. I finally ended up pinning my large prints to sheet rock.

Of course I forgot all of these challenges the other day when I finally created an ImageOn test strip that I liked. I thought all I would have to do is print out a 4″x6″ PDN Tonal Palette, make some adjustment curves for PhotoShop or QuadToneRip, and then I would be off to the races making 16″ x 32″ plates.

Turns out I was wrong. After making a new matboard carrier for the larger, 4″x6″ plates, I found that it wouldn’t feed through the front slot on the Epson 3880. A quick Bing search showed that lots of people on the internet have problems feeding odd materials through the front feeder. I considered a bunch of theories, including

  • Epson’s “check paper size” feature was failing because the carrier wasn’t exactly 8.5″ x 11″.
  • Epson’s “check paper size” was failing because the carrier’s edges weren’t completely square.
  • Some of the feed rollers couldn’t get a purchase on the material because they landed in the gaps between the matboard and the ImagOn.
  • The light sensor on the print head was falsely detecting the paper edge when encountering guidelines that I printed onto the bottom part of the carrier.
  • The light sensor on the print head was falsely detecting the paper edge when running across the edge of the window opening.

I tried disabling the “check paper size” feature and this allowed the carrier to load, but the image was printed about an inch higher on the page than expected.  After consulting the manual, I also found that Epson requires the “check paper size” be enabled when using the front feeder.

This evening I spent quite a bit of time examining my working carrier and my broken carrier to see if I could divine any difference, other than the window size. I then carefully constructed another carrier.

While conducting experiments with the new carrier, I came to the opinion that the problem may actually be the thickness of the carrier. My first two carriers were 2.5mm thick, which is 1mm thicker than allowed in the front slot. Since the first carrier worked, I assumed that Epson left a little leeway in this specification. After a number of experiments, though, I suspect that the drive wheels sometimes can’t push the 2.5mm carriers through. My guess is that the larger carrier bows just a bit more around the window edge and this causes it to get hung up.

My main evidence for this theory is

  1. The carrier would stop moving, but I would hear the rollers slipping against the paper for 30 seconds or so before the printer gave up.
  2. I seem to be able to reliably load 1.5mm window mats of various dimensions when I leave off the backing paper.

My plans, moving forward are to reexamine the thinner carriers. I had moved away from the thinner carriers because I suspected they were leading to printer head strikes where the ImagOn protruded above the surface of the carrier.

In retrospect, I am not confident that I had the platen gap set correctly. I had set it in the Epson driver, but I noticed from time to time that it would get reset to “Standard” gap. I also realized that QuadToneRip can’t set the platen gap, so it must be set from the printer’s control panel. With this in mind, I want to do some more tests with the thinner carriers, using the “Widest” platen gap setting from the control panel.

ImagOn DTP at 1440dpi

This evening I dialed in exposures, while enjoying the absence of printer banding on my plates. I made a print from the 1440 dpi plate that I created using QuadToneRip. The images below compare prints from the 720 dpi plate created with the Epson driver and the 1440 dpi plate created with QuadToneRip. Both prints were made by printing directly to the ImagOn emulsion.

The value scales from both prints look excellent. In fact, they are much smoother than anything I created using an aquatint screen. I guess my screen is really coarse.

My exposure experiments show that the process is stable and repeatable, so now it’s time to make some adjustment curves and then I can finally get back to making art!

10% step printed with the Epson driver at 720 dpi. This image is magnified – the number 10 in the upper right is printed at 12pt.

10% step printed with QuadToneRip at 1440 dpi. This image is magnified – the number 10 in the upper right is printed at 12pt.

Watch those fingerprints!

Handy tip: never ever touch the ImagOn emulsion with your bare fingertips. I know this advice seems obvious, but it is easy to do and it will ruin your plate. In the picture below, I touched the ImagOn before printing and the fingerprint still showed up. Normally one shouldn’t be touching the emulsion at all. This was one of the plates that I burned with the hair dryer, so I had to peel the protective plastic off before inserting the plate into the carrier for printing. When I inserted the plate, I pressed down on it to stick it against the adhesive in the carrier. My recommendation is to avoid burning your plate so that the protective plastic is easy to remove and can be removed after inserting the plate into the carrier.

First ImagOn DTP

I finally had a chance to print my first ImagOn DTP test plate. It turns out I was so excited about examining the plate itself, that I forgot to reverse the text so that it would read correctly in the print. The print was made with Akua Mars Black ink right out of the can, on damp Rising Stonehenge. My take aways are

  • It is possible to get a full value scale using ImagOn DTP.
  • 720dpi gives pretty decent results and is actually better than some coarse aquatint screens. I can see the individual dots but they look very uniform.
  • The plate might be under-exposed. I will have to do some more test strips to find out. The nice thing about ImagOn DTP is that it uses the very high density matte black ink, so it should have a wider exposure latitude than techniques that use transparent inks in conjunction with an aquatint screen.
  • I will have to make some adjustment curves to linearize the output. I can either make Photoshop curves, or QuadToneRip curves.

The printer head strikes are clearly visible in this print. It is nice to know that my new carrier eliminates the head strikes.

This test strip demonstrates that it is possible to get a full value scale by printing a dithered dot pattern directly to an ImagOn plate.