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

Re: continued solarplate notes

That's great Chris. Congrats on your results and thanks for the report. I'd love to see the comparison. Some questions:

Which of your theories are your referring to? The screen/image ratio theory?

Did you expose image first or screen? How were you creating the poly plate sandwich? With a contact frame in both instances?

Also, what's the size of the plates you tested? Also, can you post the brand/model of the UVBL tubes you're using Chris? Sorry if you've already done this.

If you're right, and the tests are scalable, I will formally retract my blanket statement that UVBL is bad for poly plates on the whole, and will admit that I was wrrr...wrrr...wrong. Unless someone has developed a better workflow that changes things for the better somehow, I will maintain that UVBL is definitely a problem when using Solarplates larger than 8x10, however.

In my world, I'm currently recalibrating my standard adjustment curve to work with the new 7800 in my basement. Just a giant version of the 2200, really. Ink carts are like the size of VCR tapes, which is pretty wild. The only high-tech object I own that is larger now is my car. 8-D Max density is lesser on the 7800, as has been reported, but the 1440 dpi output I had been using on the 2200 was actually much, much thinner than the 7800's output at 2880 or 1440. I created the adjustment curve by looking at the transmissive values of a step wedge printed out using my old curve on my old printer/media using my scanner. I then printed out an unadulterated step wedge on the 7800, read the values of it, and charted the differences. I then built a new curve from that data (several, in fact), printed them all on an 8x10 piece of OHP, made the plate, made several prints. Looked at print #4, and tweaked the best curve... Will wash, rinse, repeat as needed.
I tested the new Pictorico OHP Ultra's last week and found its added base density to be over the top (way too cloudy white for me and my workflow with poly plates), so I exchanged it for a roll of the regular Pictorico OHP. Pictorico wasn't happy, but they were accommodating. :-) I should have just asked them to send me samples...
I'm hoping the roll OHP isn't much different than the sheet OHP media. Does anyone use, or recall anyone else using, different curves for roll vs. sheet standard Pictorico OHP?

I'm also developing another curve for a roll of this AccuArt2 transparency media (remember that stuff?). I've had a roll of it in my basement for a couple years now. Has very little base density compared to Pictorico OHP, which is way better for me than having too much imposed density in the media's base. Once that's worked out I'm hoping to have some things to post that aren't just step wedges (though they'll be those too I assure you). :)

Now pursuing two leads on the finer 1800 dpi stochastic screens and will keep you all posted. Also, not sure if I mentioned this, but Harold at Box Car has confirmed the availability of A1 sized KM73 plates (23x30-ish). Pricing is comparable to his current prices, however it takes 2 months to get them from Japan. :-o I'm placing an order soon and hope my current workflow supports doubling the plate size. If not, I can always cut them down, as one of my clients who wants me doing bigger plates for them, reminded me. :-) Wish me luck with that...in about two months. :-P



Christina Z. Anderson wrote:
Well, results of two tests, for whatever it is worth:

I proved to myself my theory holds water. I did a solarplate at 8 mn aquatint/8 mn positive in full on direct HOT sun. I normally expose solarplate 3.5/3.5 to 5/5 under 15 watt UVBL. I got a perfectly beautiful tonal range of 7 stops from white to black.

Considering that Mike Ware says the sun is several times more powerful than UVBL (anyone know the exact comparison?) this is enough proof to me that there is a quite wide range of acceptable exposure and that the ratio is where it's at.

I exposed a KM73 plate to 8 minutes (!) aquatint but cut the positive exposure to 3 mn to relate to my 2 mn/45 ratio I found under UVBL with this plate (haven't tried the 49/41 ratio outside yet) and sure enough I got a usable image, although a bit on the bland side. Same hot sun, direct sun, but the deepest black on it corresponds to 1 stop less black than the solarplate deepest black. This stands to reason since my solarplate exposure is usually 2.5 to 3.5 more than the KM73 plate exposure. To have a range of exposure from 49sec/41sec UVBL 15 watt to 8mn/3mn outside full sun is a pretty dramatic indication of latitude.

Interestingly, I don't see a (dramatic or otherwise) difference between the sun exposed plates and UVBL, yet, anyway. I got four Newton ring spots still even though I powdered both sides of the screen and positive and the top side of the plate.
The end,

----- Original Message ----- From: "Jon Lybrook" <jon@terabear.com>
To: <alt-photo-process-l@usask.ca>
Sent: Sunday, April 08, 2007 5:25 PM
Subject: Re: continued solarplate notes

SusanV wrote:
Jon, the Dan Weldon screen isn't that dense at all.  I'm getting the
same exposure times as you are, adjusted for my 1000k lamp.

Hi Susan,

You may be getting the same exposure times at different wattages, and but we're also using very different screens. 80% density indicates coverage of dots (dpi), not density of the "tone". Every dot is 100% opaque - at least that's how the plate should see it with a proper screen. Both our screens may have "80% density", but the exposure times (and perhaps ratios) between them will vary using the same light source. Are you doing the exact same screen/image times as I am? If so, it could be worth examining, or could be coincidence...I don't know.

Another thing about longer exposure and the undercutting of dots...
that's not really the same as a finer screen.  The dots would be
smaller, but they still number the same per inch so the space between
would just be larger.
That's true, but I'm suggesting it's similar in the end result. Undercut dots in the screen exposure would lower the density *effect* of the screen on the plate from 80% to something less than 80%,. In both cases the dots are smaller, which is what allows more shades of gray to be produced. There's certain to be other differences...of course. My point was if that particular author was getting good results using our plates with 1K exposures for 15 minutes, Chris may well be correct that the exposure times ratio is more important than the actual times, BUT I'll bet he gets better results than others using lower exposure times (assuming the ratio is the important thing) because his dots are smaller. Just an idea. Difference between 10seconds and 15 minutes for the same media is quite a variance...