I have been working with gum over Pd. and discovered that I need to preshrink my paper in order to maintain registration when doing the subsequent gum layers. I have done testing and determined that two one hour hot water baths (bath, dry 24 hours, 2nd bath, dry 24hours; ready for Pd.).
I discovered that after this preshrinking the Dmax has changed for the Pd. print (gone done). The only difference is the paper has been preshrunk.
Here is the data: paper is Revere Platinum. I use pipettes to measure chemistry. Pd to FOx to T20/10% to 1.25% Na2 ratio is 1 to 1 to .1 to .05. For example when exposing a 21 step Stouffer step chart my chemistry mix is 250 ul of Pd., 250 ul of FOx, 25 ul of T20/10% and 12 ul of 1.25% Na2. With this chemistry mix on Revere Pt. paper I am getting a Dmax of 1.34.
Using preshrunk Revere Pt. paper my Dmax is 1.23. (I also had to increase my exposure amount to get a maximum black for this paper.)
I develop in room temp (~68F) KO. I use a Nuarc metal halide exposure unit with the PPM2 to “time” my exposures. With these tests my studio RH has been no less than 45% (as high as 55%). I rod coat. Air dry for 5 minutes, heat dry for 5 minutes, then “relax” the coated paper in a sealed water humidity tank for 10 minutes; then expose.
I am thinking that the hot water baths are removing the internal sizing from the mill and perhaps even changing the pH of the paper thus effecting the Dmax.
If you have any thoughts on this I would appreciate it but I really just want to check to insure my QTR settings in PiezoDN workflow are correct.
This is something that maybe someone like Pradip would know better about re: sizing. All I would suggest is maybe mounting the sheet to plexi or aluminum and then doing all your coats and dries with it mounted so it does not shrink. Dunno if that is possible . . .
“I am thinking that the hot water baths are removing the internal sizing from the mill and perhaps even changing the pH of the paper thus effecting the Dmax.”
Hello Michael,
I think your guess is right. The Revere Platinum is internally sized, but immersion in hot water for any extended period will change the physical, and most likely the chemical structure of any paper. It is hard to tell exactly what is causing the significant change you describe, but you should consider:
preshrinking in distilled water, being exact about all the variables with this step (time, temperature, drying procedures) and then keeping these as a constant part of your work flow
then, if you are building your own quads (it seems that this is the case from your screen grab), make one for preshrunk paper.
I am treating this treated Revere Platinum paper as a new paper. And therefore building a new linearized quad after determining my base exposure amount using the Stouffer 21 step film.
There have been quite a few printers working with multi-layer processes (or layers of multiple processes) who mount the paper to a non-expanding substrate like aluminum or plexiglas as Walker mentioned. The idea goes back to Irving Penn’s multi-layered prints if not further. The late David Chow was one recent practitioner I can think of who wrote about it. Unfortunately his website appears to have been taken down.
for metal it is good to use slightly acidic paper. I would soak the paper in an acidified water solution of 1-2% oxalic acid.
Perhaps your wash lowered the acidity of the paper.
