TiO2 in both the Anatase and Rutile form absorb a LOT of UV radiation and therefore could increase exposure time by making less UV available for the "real" exposure. The light sensitivity that they talk about is related to internal energy transfer from light and UV absorption, and this makes TiO2 a very good substrate (alone) for electronic (digital) imaging.
CMB shared an interesting tip with me the other day in a PM, and he said it was OK to share in this thread:
Originally Posted by CMB
It seems you've located a source for Hardener No.3 (Diazidostilbene Sodium Sulfonate) and the next thing to do is figure out how to use it.
When testing it, I recommend that you keep in mind Kosar's statement that it can be used in a similar fashion as dichromate. Thus, if you are used to making up a three percent PD solution and tray soaking for however long, do the same with the Hardener #3. Be careful that when mixing it with water, you do not allow the temp to exceed 85F. Try not to change anything in your technique except substitue Hardener #3 for dichromate. It will be a good place to start...
Well done! I will be interested to hear how it goes. How are they shipping it?
I am waiting for a coating rod to arrive from the group order that was organised elsewhere and then I am going to try making a colour print with halftone seperations and my screen printing sensitiser stuff. I could pour without the rod but it is easier to just wait.
Intend making some next weekend if the rod arrives before then. The permanent pigments (see Nadeau) can be had at paint mixing places. CMYK seperations can be made (without photoshop) using Gimp with the Seperate+ plugin and turned into halftones using the newsprint filter. Contrast is then not a variable, leaving only exposure/pigment load to get right. Registration is another story but I will try a big carpenters square to to get started. I am going to try the double transfer system in Tod Ganglers videos so I dont stain the final support with my screen printing sensitiser. Apparently registration can be a problem with single transfer except with something like yupo which is reasonably dimensionally stable. I am not shure that halftones are the way I want to go but it is a good place to start exploring. Non CMYK prints can also be made using duotone and tritone seperations and halftone negatives, without the frustrations of curve building so its a process worth exploring. Obviously QTR curves or real negatives are the ideal.
Good luck with your color tissues and prints. One concern is whether the clearing baths may have a negative effect on the pigments. I would recommend making some un-sensitized samples so you can do a before- and after-clearing comparison to see if there is any color shift or other damage.
As I understand it, these pigments are generally very chemically stable. I had not thought to check at paint mixing places, but I got a set of CMY pigments from Lansco Colors. I followed Nadeau's recommendations as well as I could; Quinacridone Magenta 122, Phthalo Blue 15:3 and Yellow Azo 155 (not sure about this yellow).
The half-tone route does sound appealing for the reasons you state. Are you going to try to turn them at angles to avoid moire or just go for it?
Really looking forward to hearing about your experience with this!