On Mar 30, 2006, at 8:03 PM, Christina Z. Anderson wrote:
>
>
> The 6 minute printing time, given UVBL and 15% dichromate and my
> workflow gives me a layer that develops in an hour and yet can also
> be spray developed without the layer sloughing off. It also
> provides a deep enough colored layer. At 5 minutes it is not bad
> either, but the layer of gum is a bit more tenuous and not as
> strongly colored--the more exposure, the deeper the gum layer is
> and hence the more pigment remains on the paper. At least, in side
> by side step wedges exposed at 1, 2, 3, 4, 5, and 6 minutes this is
> the case--the colored layer thickens and therefore deepens with
> exposure. If my website ever gets up it'll show this little example.
Well, of course, all of this goes without saying: for each
combination of light, dichromate, film, paper, etc etc there is a
"best" exposure, which can easily be determined with a step wedge,
and which produces the optimal hardening of the gum layer; anything
less than that exposure will result in less than optimal gum
hardening. I would be very surprised if there are any gum printers
who don't know that.
But my point, which I wonder if you've missed, was that this
"best" exposure is different for every system of equipment,
materials, etc. It's hardly surprising that your students found that
the same exposure worked for them, given that I would assume that
they would be using the same equipment and materials, but surely
you're not suggesting that 6 minutes is an optimal exposure in some
kind of general and absolute sense.
Katharine
Received on Fri Mar 31 00:04:01 2006
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