Progress! But remember: baby steps. Still, today’s baby step is a bit of a symbolic one, because it’s the first actual carbon transfer color image. With some caveats. Well, not some. Many. But still. Colors!
As I wrote yesterday, I made a stupid mistake printing my first set of color separations by printing the cyan, magenta and yellow negatives as…positives. I found out about my mistake as the carbon prints were already drying, so that put me back a bit. I’m still using those to practice the dual transfer routine in anticipation of an exposure-time alignment solution. So many things to work on!
This morning, I had the chance to print a new set of separation negatives and also print them as carbon transfers. Coincidentally, I discovered a few days ago that the laser transparencies I once bought for PCB making work very well indeed as temporary supports for dual transfer. Convenient, because my (very, very) old HP LaserJet 4P doesn’t print very good solid blacks, so the transparencies turned out to be useless for making PCB’s. But that’s a different story, for a different day. So back to the carbon transfer front: I made a set of transfers onto the shiny transparency material. And that of course, enables me to do this….:
Yeah, it’s a crappy phone image and yeah, there’s close to a million issues with it in about a thousand ways. First of all, what are we looking at here? Well, it’s a stack of carbon transfer transparencies, from top to bottom: yellow, magenta, cyan and black/key. The colors were the tissues I made earlier with the gouache and watercolor paints at 2% w/v concentration. The black tissue was my standard 1% India ink tissue, which I developed for lower contrast than the other ones. Turned out not too bad for a really wild/blind guess.
And will you look at that, it has all these fancy colors in it!! Ok, not necessarily the right colors in the right places, but it’s still a kind of magic, seeing those four layers add up to something that at least remotely resembles the torture test color checker chart I made yesterday.
So, what’s good about this? (I need to remember to celebrate my successes because it’s supposed to keep me motivated or something.) First of all, most of the colors actually printed. There are (virtually) no black patches where they’re not supposed to be blank, and the blank patches are in fact pretty much blank. Secondly, the different hues at least approximate the image as I designed it. We’ll evidently get back to this later. Thirdly, if you look at the rainbow strip at the right-hand side of the image, it looks pretty much like you’d expect it to: it’s a continuous gradient across all hues ranging from red back to red. So all considered for the first real color assemblage this is really quite nice, if I say so myself!
Now, how about the millions of issues? These are (1) more plentiful than the successes and (2) also set the stage for further work, so pretty darn important. Let me try to address the main ones.
The highlight problem. I noticed in the separations that there’s actually quite a few patches on all three of them, but mostly on magenta and cyan, that are pure white while they should have a little tone to them. This is actually the Achilles’ heel of carbon transfer: the difficulty of printing very slight tones that border on white. Looks like mine are washing away, and that comes at no surprise.
I’ve got two options here: (1) stick with continuous tone negatives and be very careful in a couple of things. I’ll have to reduce pigment load to the bare minimum to get good saturation so I can keep the heaviest gelatin layer possible for the lightest tones. I don’t expect this will actually be sufficient, so I’d have to resort to making two or more separations for each color; a highlight and a shadow separation. I might also have to revise my rather brute force approach to print development, which currently involves washing away undeveloped gelatin by pouring hot water from a jug onto the print. Mind you, this works surprisingly well and surprisingly thin patches of gelatin do adhere. But I’ll have to push the limits here and the brute force approach may not cut it anymore.
The second option (2) is to abandon continuous tone negatives and move over to halftone screens. This is what Calvin Grier from thewetprint.com does and it’s understandable why. Halftone screens in principle offer many advantages, which in this application essentially boils down to that it’s just easier to print tiny dots that are either tone or no tone, than to print an infinitely refined scale of tones ranging from full tone to no tone at all. By then making the dots really small and arranging them smartly in terms of size and distribution, you can produce something that is nearly indistinguishable from a continuous tone image.
However, option 2 also has some distinct drawbacks, at least for me. For one, it’s very, very difficult (and expensive) to make very tiny dots. The best I have is an inkjet printer, and that’s miles removed from the kind of quality Grieg gets with his imagesetter negatives. Then there’s the RIP (raster image processor) challenge of getting a continuous tone digital image translated into a sensible dot pattern. Fortunately there’s still Quad Tone Rip which I used in the past for making polymer photogravures (NB: I sold off the etching press a few years ago, so currently not doing this!) I just ran a quick test with QTR and it seems I should be able to make somewhat passable negatives for carbon transfer this way, but very light tones will just a small number of dots at huge distances from each other, so it’s a really compromised solution.
So both options are rather challenging and may either be dead-end streets, or involve huge investments financially and in any case in terms of time. Essentially, this leaves me pretty much empty-handed for the moment, so I’m going to think about this some more. I knew I would run into this at some point, so it’s not a huge disappointment. I just want to see how far I can push this on a shoestring budget and with household materials, so an imagesetter is definitely not in the stars for me.
Color balance issues. Well, it’s kind of evident because I’ve done no calibration to this point whatsoever, apart from working out an approximate adjustment curve to match the negatives to the carbon transfer process. Mind you, the same curve adjustment for all four colors! It’s surprising it works at all, if you think about it. The most glaring color problem at this point is that magenta is far stronger than the other colors, making for instance the blue column (well, it’s supposed to be primary blue…) shift to magenta too much.
I might just head out to the shop and get some more gouache and water colors; I decided I might give a full gouache set a try, using the Talens gouache line. Also, I want to get the Winsor & Newton watercolors in the full CMY set (I’ve only got C currently, for testing) as a backup. Or maybe the gouache is going to be the backup, I don’t know yet. One note about gouache: this is essentially a watercolor type that is opaque. You’d expect this to be a problem with carbon transfer, because to get the C, M and Y to mix well, you want transparent, not opaque, pigments. But of course in a carbon tissue, they’re diluted to such an extent that the opacity of the gouache medium as far as I can tell does not play a significant role.
Hopefully a simple adjustment of the recipes for the C, M and Y tissues will even out the color balance. There is of course a chance I might have to do some additional curve doctoring, but so far, what I think I see is a fairly nicely linear behavior of the carbon tissues.
Key layer density matching. As indicated, I’m using my standard 1% Talens India ink tissue for the key layer. I notice it’s a bit heavy, so I’ll have to reduce contrast a bit. I’m already sensitizing it with 1ml of a 16% dichromate solution, so that’s pretty much maxed out. I don’t want to throw even more dichromate at it, because (1) dichromate is a necessary evil at this point and there’s just no need to overdo it, and (2) making even more concentrated dichromate solutions is virtually impossible and increasing the amount I use (e.g. 2ml or 4ml for a 4×5″ tissue) will extend drying times, and I don’t like that. I want my tissues to dry swiftly, within about half an hour. They do that just fine right now, so I’ll leave that parameter alone.
The obvious solution is to decrease the blackpigment load in the glop. The other day I happened to pour some 0.25% ink tissues (also a highlight-related story I might follow up on later; but this was for B&W images) and in terms of density, I bet they have more than enough oomph to work as a key layer for CMYK. They are a bit too weakly pigmented to work standalone as B&W transfers, but that’s beside the issue now. Combining 0.25% ink load and a fairly strong sensitizer, I think I can get a nicely smooth and subtle key layer.
Layer construction issues. There’s an assortment of smaller issues I need to work on; particularly layer order and registration. Currently, I’m doing the ordering visually, by simply laying the carbon transparencies on top of each other and seeing which order works best. I’m also using Grier’s insights as expressed in his Gum Printing manual.
But I’ll also have to fix the registration matter at some point. Right now, I just carbon print each layer separately onto a transparency, and then transfer them onto the final support one by one. This allows for optical alignment based on the image itself. It’s a bit iffy, but it kind of works, and it’s how I did my very first CMY attempt. But I feel I’ll have to somehow figure out something that works more reliably, especially when I’m going to transfer all layers onto the same transparency so I can then transfer it to the final support all in one go. I’m pondering about some kind of DIY pin registration system using an office perforator and some 3D-printed parts. No clear idea yet how it’s going to work, but there’s something in there, I think. Again, the aim will be a shoestring budget solution that works with common materials. Yes, I could acquire a pin registration punch and all that goes with it, but where’s the fun in that?
Ok, that’s just about 4.5 or 5.25 issues from 1 million. I may have exaggerated the 1 million, but there surely are many more issues I could list. The thing is, the above ones are the most pressing for now, so that’s what I’m going to focus on next. Stay tuned!