U of S | Mailing List Archive | alt-photo-process-l | Re: Yellow tents and UV (was: outdoor gum demo)

Re: Yellow tents and UV (was: outdoor gum demo)

Forgive me if I am chiming in and TOTALLY misread this thread because I have only read half the posts. Loris, I am completely in your camp on this one, though, Paul, I do not have a UV meter but searching on the web there seems to be quite a difference between 4 and 9, so much so that I am incredulous you don't find a difference, but maybe it is just where I live that makes me feel that "say WHAT?" way....

I used to print outside continually when I did not have a UVBL light box (and my very first alt professor (1997) taught that way whereas now we all seem to own/build our own UVBL units), and in Montana the difference is dramatic enough winter to summer and time of day that I didn't even hardly BOTHER printing in the winter months much, nor did I print past 2 PM. For example, a 30 second gum exposure in good spring or summer sun would equate to 20 min or MORE at other times and seasons so it became not worth it. I only printed, therefore, when I could print from 10-2. Summer these hours would, of course, be extended until maybe....5?

I know this for a fact because I used to record all my exposure times for all my colors, keeping rigorous records for such a variable (sun) source.

But one would have to take into account altitude, latitude, so many other factors that there is no way to quantify this with any sort of anectdotal information I would suppose. In Montana I am at 5000 feet, and the seasons are an incredible change as is sunlight strength at my latitude.

Our adage here in the ski mountains amongt the pro-patrollers is that until February 1 you can get away with not wearing sunscreen, but after that date, sunburn was a fact. My husband was a professional ski patroller for 14 years and this rule of thumb served him well with his very Irish/English heritage.

NaTHNaC | Sun Protection Information Sheet, Travellers

I would agree with Loris that a POP or partial POP process might give a skewed impression and even gum with its immensely forgiving exposure range might skew a very specific measure of quantifiable information, but the latter IME is skewed very much to Loris even so.

I remember being SO excited with my first UVBL unit because finally I could print in the winter and at night! And actually quantify!

But heck, Paul, if it works for you that is great! You inspire me to go out and print some step wedges....no....on second thought, I'll stay inside with my UVBL.

Christina Z. Anderson
----- Original Message ----- From: "Loris Medici" <mail@loris.medici.name>
To: <alt-photo-process-l@usask.ca>
Sent: Tuesday, April 21, 2009 11:22 PM
Subject: Re: Yellow tents and UV (was: outdoor gum demo)

Which process is that and what was the exposure time? I did notice a
difference (albeit not linear as I first predicted - have to work on this)
with traditional cyanotypes. Maybe it's because at fast printing times it
could be harder to notice any difference and/or self masking plays a
significant role... ???

Anyway, I'm ready to eat my assertion (and go to the corner on one leg) if
someone comes up with an quantitative explanation to why giving the same
source (the sun) UVA intensity remains the same whereas other types of
irradiation seems to change intensity.


22 Nisan 2009, Çarşamba, 5:36 am tarihinde, Paul Viapiano yazmış:
Remember when we were talking a little bit re: this on the Hybrid forum?

So far, I've noticed no change in exposure times from UV Index 4 through
index 9 when exposing via the sun...