Re: continued solarplate notes
Susan , Chris
I know very little about photogravure but I do know Danish - my native
language - so here comes my translation of the text by Eli Ponsaing :
UV light, mercury lamp hbr 125, coil bhl 125 or 144, metal halide lamp ,
xenon lamp. Not all sources of light are suited for our copying. Wavelengths
from 400-360 micron in the ultraviolet spectrum are needed. By the use of
FP-plates for photogravure a punctual light source is the best, which has so
small an extension as possible. This kind of light is found in mercury lamp,
sun lamp, xenon lamp, metal halide lamp and carbon arc lamp.
I hope this helps you.
----- Original Message -----
From: "SusanV" <firstname.lastname@example.org>
Sent: Sunday, April 08, 2007 5:15 PM
Subject: Re: continued solarplate notes
thanks for taking time to post this info! Very interesting stuff. I
look forward to someone jumping in here to translate... one of the
many nice things about this list :o)
On 4/8/07, Jon Lybrook <email@example.com> wrote:
\Christina Z. Anderson wrote:
> 2. Exposing is done in 3 stages--main exposure first for **15**
> minutes with the light source at 1/2 the distance of the aquatint
> exposure. Aquatint exposure SECOND--**15** minutes with the distance
> of the light 1 1/2 the diagonal of the vacuum frame measure. Post
> exposure 5 minutes. (on a Stouffers dark steps 8, 9, and 10 should be
> "clearly defined").
Maybe he's using a maglight to make his exposures. ;-)
> With the inverse square law of light 1/2 the distance of the positive
> means it is 4x the length of exposure, correct? So Ponsaing's ratio
> of exposure is 4pos/1aquatint. Can you believe the length of his
> times??!! I can't read the text to see what his light source is,
> though, unfortunately. I can glean that he is using Japanese plates
> Oh, here are his light choices: "uv lys, kviksolvdamplampe hpr 125,
> drosselspole bhl 125 eller l44, metalhalogenhampe, xenon lampe. And
> then Ikke alle lyskilder er egnede til vor kopiering. Der kraeves
> lysbolgelaengder mellem 400-360 my i det ultraviolet-te omrade af
> spektret. Ved anvendelse af FP-plader til dybtryk, er punktlys bedst
> egnet, d.v.s. at lyskilden har sa lille en udstraekning som muligt.
> Dette lys findes i kviksolvdamplampe, hojfjeldssol, xenonlampe,
> metalhalogenlampe og kulbuelampe.
> My interest in the light source choice is to compare his longer
> exposures with what we are doing with KM73s. What he is doing is
> still not disproving my theory that the length of exposure is not as
> crucial as the ratio, unless, say, he is using REALLY weak bulbs which
> I don't think is true--I can at least decipher halogen in there. But
> it still supports the theory that, like gum, the longer exposure (to a
> point) the thicker the layer of goo on top of the substrate, whence
> comes Welden's description of the forgiving latitude of exposure of
> the plates, that exposure is not so crucial.
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!
gravure blog at www.susanvossgravures.blogspot.com