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.

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 . . .

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.

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.

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.

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.

In my earlier ImagOn direct-to-plate experiments, I managed to print an aquatint pattern with sufficient density by running my plate through the front slot of an Epson 3880 printer. The dot structure in the matrix looked fantastic, but it was interrupted by streaks which I determined were the result of the print head striking the plate.

When I printed the plate, I set the platen gap to the maximum, but for some reason this wasn’t sufficient the prevent the head strikes. It turns out the problem was in the design of the plate carrier.

One of the nice things about ImagOn is that it is transparent. Transparency allows one to spot inking and wiping problems by holding the plate up to the light and it helps in registration when printing with the paper under the plate.

The problem with transparency is that the Epson 3880 uses an optical sensor to detect the paper, and it can’t see the plate because it is transparent. The solution is to attach the plate to some sort of an opaque carrier. Some people just use a sheet of paper.

For my first attempt, I constructed a carrier with a window mat on top and a piece of cardstock on the bottom. The plate was held firmly in place inside the window with some Tombo removable adhesive strips.

The Epson 3880 specifications allow a maximum paper thickness of 1.5mm. With this in mind, I chose to make my first carrier out of Strathmore 400 4-ply Bristol and Epson Brochure and Flyer Paper. The combined thickness is about 1mm, and well under the limit for the Epson printer. The problem is that the Bristol is 0.030″ thick – the same thickness as the polycarbonate plates. When the plate sits on top of the adhesive strips, a portion of the plate and the ImagOn emulsion protrude above the surface of the carrier, just begging for a head strike. Any warping in the plate will only make matters worse.

This carrier is too thin. The ImagOn plate protrudes above the surface of the carrier, increasing the probability of a head strike.

Today I tried a thicker plate design and it worked. I ended up using Crescent 4-ply mat board on the top and Strathmore 400 4-ply Bristol on the bottom. This carrier has a total thickness of 2.25mm, but it seems to work fine in the printer.

This 2.25mm carrier seems to work fine in the Epson 3880 front feeder and it eliminates head strikes.

When making the carrier, it helps to print the outline of the plate directly onto the Bristol that will become the bottom layer. Print this sheet using the front feeder so that the plate outline will be aligned correctly.

Here are some pictures of the second carrier.

My new carrier uses a layer of Strathmore 400 4-ply Bristol on the bottom and a piece of Crescent 4-ply matboard on the top. Note that I have printed the plate outline onto the Bristol.

The plate is held in place with strips of Tombo Removable Adhesive.

I spent last night printing – just not with the etching press. Instead I used my Epson 3880 to make test strips – a lot of test strips.

This is way too many test strips, but it seems like there are a million variables to explore.

My goal was to figure out the right printer settings and workflow in order to print directly to ImagOn plates, bypassing the need for transparencies and eliminating the dedicated aquatint exposure.

As I mentioned in my earlier post, it is possible to incorporate an aquatint-like structure into the image to provide the small ink wells that prevent an open bite in the dark areas. I am currently aware of four approaches for incorporating the aquatint into the inkjet output:

1. Printer Driver Dither. In this approach, a gray scale image is converted to a dither pattern of solid black dots in the manufacturer’s printer driver. If your printer driver has a black-only mode, this is one of the best approaches because the dither can be accomplished at any of the printer’s native resolutions.
2. 3rd Party RIP Dither. Some printers like the Epson 3880 limit black-only mode to lower resolutions. This can lead to a grainy image in the matrix. One can use a 3rd party RIP like QuadToneRip to generate a maximum resolution dither pattern. The downside of this approach is that it involves a lot of experimentation to get the RIP configured correctly. I’ve also found that the Epson driver seems to generate a smoother dither.
3. Photoshop Diffusion Dither. In this approach, a grayscale image is converted to a bitmap using Photoshop’s diffusion dither. Conceptually this is similar to the algorithm in the printer driver and the RIP. In practice, it can generate a lower quality dither on the plate because the dithered image from Photoshop may get dithered again in the printer driver or RIP. One can reduce this effect somewhat by choosing bitmap resolutions that are power-or-2 factors of the printer’s resolution. One can also eliminate any print-time processing by using a driver like GutenPrint.
4. Photoshop Stochastic Screen Layer. I describe this approach in my earlier post. The goal is to more accurately mimic the effect of an aquatint screen. In the first three approaches, the density of dots decreases as the image gets lighter. This can have the impact of reducing resolution in the lighter shades. A stochastic screen layer has a uniform dot density across the value scale, and uses gray levels or even colored inks to adjust the value. This approach has a couple of downsides. As with the Photoshop diffusion dither, one has to guard against additional dithering in the printer driver and RIP. The other downside is resolution – the printer only has a limited ability to adjust drop size, so gray levels will still need to generated by some amount of dithering. This means that each pixel in Photoshop will need to correspond to a handful of pixels in the printer.

Last night I focused my efforts on the first two approaches, with my first test using the Epson printer driver at 720dpi. My goals were to figure out sufficient dot density while avoiding excessive dot gain and banding. Factors that impact density include choice of ink, print resolution, print speed, and the color density setting in the advanced media control options. Factors that impact dot gain and banding are paper thickness, platen gap, and drying time per print head pass.

After examining many test prints under a loupe, I finally arrived as some settings that seem like a decent starting point. The results shown below are from the Epson driver with the following settings:

• Media type: Epson Singleweight Matte Paper (this is one of only two media choices that enable black-only printing – other Epson printer models enable black-only printing for a wider variety of media and resolutions).
• Color: Black
• Ink: Matte Black (only choice allowed for this media type)
• Print Quality: Quality (720dpi – the only resolution supported for black-only)
• Paper thickness: 15 (1.5mm)
• Platen Gap: Wider
• Color Density: default value
• Drying Time per Print Head Pass: default value

Using these settings, I printed a test strip directly onto a plate consisting of ImagOn laminated to 0.030″ polycarbonate. The plate was laminated the day before printing and I waited another 24 hours after printing before exposing and developing. The plate was exposed on a Nuarc 26-1K exposure unit for 20 units. I did not use the vacuum frame. Development was the standard 9 minutes in a room temperature solution consisting of 10g soda ash per liter of distilled water.

Overall the plate looks pretty good.

Here’s a closeup of the 10% density portion of the plate. The pits are well formed and go all the way to the surface of the polycarbonate plate.

Here’s the pattern on the plate at 80% density. Again, the pits go all the way to the polycarbonate plate, and the ridges seem full thickness. This matrix looks very similar to the best plates I’ve made with an aquatint screen.

The aquatint pattern in the matrix on this plate is almost perfect! Unfortunately the matrix shows an unacceptable amount of printer banding.

The big unresolved issue is the banding you can see here at 60% and 70%. The banding appears throughout the value scale, but is more pronounced in the darks.

Printer banding has many potential causes, but the most common are misaligned print heads and head strikes due to incorrect paper thickness, insufficient platen gap, dust and particulate on the print head itself, and warped media. The photo below shows clear evidence of head strikes. The fact that the banding does not go all the way across the plate suggests that the plate wasn’t completely flat, allowing a head strike for a portion of the scan.

This image shows evidence that the banding is produced by head strikes. The vertical scratches on the left of the plate are in a non-printing area, thus indicating that the head is dragging across the plate.

It’s been a lot of work to get to this point, but I am pretty happy with the results. I am confident that I can address the banding and then I will do a PDN-like calibration to generate Photoshop adjustment curves to linearize the ImagOn response. Stay tuned for another exciting episode!