U of S | Mailing List Archive | alt-photo-process-l | Re: continued solarplate notes

Re: continued solarplate notes

So based on your theory Chris, if my ratio is 1:1 screen/image, I could do 10 seconds/ 10 seconds, or 1min/1min, or 15min/15min and it wouldn't make a huge difference? This might be true to some degree if one is using imagesetter film for both, since the density of imagesetter film is so heavy. I'd expect the dots would change size as time is increased though, since the longer exposures would allow more light to sneak underneath the edges of the dots. Easy enough to test
Thanks for the posting!
Up to a certain point and before a certain point that is my THEORY. I'll really try to blow my theory by a sun exposure of 6/4mn in MT UV rich 5000 ft elevation sun. But you, with it seems maybe the same light source as Ponsaing, are doing 11/10 SECOND exposures compared to 15/15MIN with the same plate?? That's a dif of 7 or 8 stops! Maybe you have another explanation as to why the great variance in times--maybe the aquatint is exposed on UV blocking TMax 100 :)

But if Ponsaing is using 15mn/15mn in a 4pos/1aquatint ratio essentially (given the inverse sq. law of light) it is possible with longer times that the ratio changes on some sort of curve. I don't know. I've got about 15 plates left to experiment with...what the hay, it's only time and money...

My experience is this: when calibrating the stuff, I found a 2 mn aquatint time and a 45 second positive time at first. I ended up printing my edition with this.

Then I fiddled around with it after observing my 6 test wedges and settled on 49 seconds aquatint 41 seconds positive. I also did a 50/50sec which I didn't like as well--the highlights at that point started to get blown out. Camden calibrated, too, and found a 4mn/2mn exposure time!

So, given my experience with gum, that there is a range of exposure wherein the dichromate hardens a deeper or less deep layer (with the "bookends" of that range being loss of highlights and midtones and blocking up of shadows and midtones), my wonder is if, in fact, this is true of photopolymer, that there is not one exact best exposure even with the SAME light source and conditions, but a range of user friendly exposure times, given a ratio that is correct--in other words, choose a time and then find the tonally good ratio for that time and then tweak that with a custom curve. This would explain to me the major variance in exposure times I have read everywhere.

I did that with gum--I finally settled on a 6 mn exposure time to get a deep and stable layer that allowed me to spray develop. For others, this may be over or underkill. But I chose the time NOT based on gum's standard printing time (SPT) necessarily but one based on practice--within the bookends of reason of under and overexposure.

The thing I found is that the 49/41sec plate, although tonally beautiful, too, was somewhat thin and soft. Even with post exposure in the sun til it turned blue. My wonder is if this thinner layer was why my chine colle ate the plate away right away, and that with a thicker plate the plate will be more stable. Until I test this in the sun it is only theory waiting to be disproven so there might be a letter shortly saying stop the press (figuratively)!