Maybe I'm not doing something right but I've never been a fan of QTR. It's output for me has always been subpar and error prone. I.e. unsharp results compared to the Epson driver, ink running off the paper when limits are too high etc. So recently I started looking at GutenPrint as a custom RIP for a custom B&W inkset. As far as I can tell no one has attempted this except possibly the GutenPrint developers...

I've managed to come to a working solution with GutenPrint after some experimentation. Advantages I see in GutenPrint:

* Density is easily controlled using Print driver settings - if you want a digital negative with more ink blocking you can up the density at the time of printing by changing "Output Controls Extra 1 -> Density" when printing.
* Better printer support- this procedure could be used by printers other than Epson since GutenPrint supports many more printers than QTR. The caveat being I'm not sure how many non-Epson printers have a defined Quadtone inkset type yet available for customization.
* GutenPrint has a 5760x2880 DPI printing mode for Epson printers which QTR seems to lack. Results are visibly sharper, with the disadvantage being very slow printing times (not a concern for me)
* Many many more options are customizable. QTR is based off an earlier version of GutenPrint (then known as GIMP Print). GutenPrint has evolved since so you have more fine grained control with more algorithms available for things like Dither method etc

Here's the basic procedure for using an Epson 1430 with a custom B&W inkset with GutenPrint on a Mac.

* Mix your ink as you would normally and fill up your refillable cartridges. Sandy King's recently released manual of Carbon Printing has detailed instructions on designing and creating a custom B&W inkset. I based mine off mixes of ConeColor Pro Photo black, Light black and Light light black ink available from Inkjet Mall. Since you only need 3 inks it's quite economical.
* Use QTR to print off a calibration chart and then use a scanner or densitometer to get the relative densities of your inks. I.e. Photo black should be 1.0 and has a density of say 2.0. If your next darkest ink has a density of 1.6 then it's relative density is 1.6/2.0 = 0.8
* Install GutenPrint, add a printer using the Mac Dialog box select the printer and "Select Software" to find your Gutenprint driver for your printer
* When printing go to "Printer Features" in the System print dialog.
* Adjust these settings:
* General -> Adjust resolution to 5760x2880 dpi unless you want faster printing times at the expense of quality
* Output Control Common -> Select Photograph for the media type
* Printer Features Common -> Change Inkset to MIS Six tone
* Output Controls Extra 5 -> Scroll down to the Hextone section. There should be a section for each Hextone value from 5 to 1. 5 being the next darkest ink after black. For each of the value's put in the relative density.

Make a test print. The test print should print reasonably well but will probably have transition problems. I don't quite yet grasp the Hextone transition values but experimentation has led me to put a Hextone transition value going from 0.1 for Hextone 5 to 0.5 for Hextone 1 to work well. Basically linearly adjusting the transition values for each lighter ink. More experimentation/research needed here.

Hope this helps. This post wasn't intended to be a dig at QuadTone RIP but as a starting point for those who want to experiment with different printing methods. If anything else it adds another tool to the toolbox for those using all-gray inksets.