Inkjet and water gilding

My project imagines stories told through pictures by distant future artificial intelligent machines, who rummage through humanity’s physical traces, finding mostly e-waste and some preserved works of art. I am training neural networks (GANs) to create new images from large collections of images of artworks.

Another part of this project entails taking the images made with neural networks out of the digital realm into the physical. It is an interesting process to gather digital images by the thousands and then discard them, keeping only the information encoded in the neural network (GAN), ultimately returning the images to the physical world on panels that resemble the Medieval and Renaissance panel paintings on which they based.

Late medieval and early Renaissance paintings were done on wooden panels with gold leaf background. I am using this traditional technique, using circuitboards rather than wood, using inkjet printers rather than tempera paints, and using a computer controlled machine to punch and inscribe the gold background rather than doing it by hand.

For a quick review of the process of making a panel painting on gold, it’s hard to beat this video from the National Gallery. My process is the same, except I’m using an inkjet printer instead of paint.

In a previous blog post, I posted a photo of one of these. In it, I had printed a composite portrait of a figure onto a metallized film, cut it out and adhered it to the gilded panel. Last week I ran a bunch of experiments printing on different papers, films and coatings, and this week I managed to print directly onto the fibreglass panel.

First I tried various options for transferring the images onto the gesso using a transfer medium. Bonny Lhotka’s books and website have quite a bit of information about printing and transferring onto unconventional materials. I used a popular method based on printing on the non-absorbent side of freezer paper, and then scraping the still-wet ink onto the final surface. The results I got were interesting, but not quite what I was looking for. The ink tended to bead up on the surface of the transfer paper, leaving splotches and gaps in the resulting transfer. Colours were not well separated either, as everything tended to run together a bit.

Image printed on freezer paper and transferred to plain note paper. Despite trying various settings, this was one of the cleanest results.

Inkjet printers are a marvel of technology, precisely controlling picoliter droplets onto a medium. Photopaper and other substrates are also carefully made to optimize this process. Try printing a colour picture on plain paper, and you get a blurry, wrinkly mess. Try it on a shiny surface, and you get a greasy mess.

The same test print on glossy photo paper (L) and on gold foil (R). The baby faces are as disturbing as anything a GAN can produce, but alas not what I was looking for.

I discovered the murky and mysterious world of printer ICC profiles and various settings that affect how much ink is deposited on the print, as well as a coating intended to take non-traditional surfaces (fabric, regular paper, etc) and make them suitable for receiving ink.

Two successful prints on gold foil painted with Golden Digital Ground and one curled up mess on vellum supposedly suitable for inkjet printers.

Luckily, my photo printer (Epson R3000) accepts media like posterboard up to 1.3mm thick and has a “straight through” printing path as an option. I got some 0.75mm thick circuit boards (bare copper on fibreglass) to see if I could run them through directly using Golden Digital Ground that worked on the thinner media.

This was tricky, because painting the various layers of rabbit skin glue, gesso and bole on much thicker panels causes them to warp when the glue sets. This has been a problem for the embossing phase as well. I solved it by painting both sides of the panel for the first few coats, then sanding off the unnecessary material from the back when the good surface of the panel was stabilized by the usual 6-8 coats of gesso. The usual scraping and sanding needed to ensure the panel is flat and smooth was enough to bring the gessoed circuit board under the 1.3mm maximum the printer will accept. I already know from my earlier printing tests that a “head strike”, where the print head collides with the material can be bad enough with paper, so I really didn’t want it to happen with something rigid like the panel.

The panels I have are 6″x9″ (around 15cm x 23cm), so rather small, and the printer wouldn’t accept them without crashing the software. I eventually got around this by making a holder for the panel out of a 1.3mm thick mat board used for picture framing, with a 6″x9″ hole cut to fit the panel exactly (shown below with a bare copper/fibreglass panel).

Using this approach I was able to print on fibreglass that I had treated with the Golden Digital Ground.

Copper/fibreglass circuit board panel partly coated in Golden Digital Ground with some of my latest portraits generated with transfer learning. The rightmost edge of the image at bottom left overlaps an area of the copper not treated with the Golden Digital Ground, and you can see the ink beading up on the surface there.

I took a few deep breaths before sending a gessoed panel through, but the results were quite good on both untreated gesso and gesso treated with Golden Digital Ground

Gessoed circuit board panel with inkjet printed figure. Washers were used later as spacers to keep a dust cover from sticking while everything dried.

I then made a stencil that matched the outline of the figure and sprayed the inkjet painted part with lacquer to protect it from the water used in the next step, applying the bole.