RE: gloy for tricolor on yupo?

Yves,

I think Chris has responded to your post but I might add this. Using a
Stouffers step tablet allows one to monitor the process without the
confusion of a digital negative and digital step tablet. Getting a really
good process adjustment curve is a bit more than child's play too. It can
take a fair bit of work to get one that is all but perfect, at least in my
experience.

Don Bryant

-----Original Message-----
From: Yves Gauvreau [mailto:gauvreau-yves@sympatico.ca]
Sent: Friday, March 31, 2006 8:52 AM
To: alt-photo-process-l@sask.usask.ca
Subject: Re: gloy for tricolor on yupo?

Hi,

when I see below that one should use a step tablet to find proper exposure,
I would suggest a couple of reason to be doubting these measures. First,
unless the material you use as your negative is exactly the same as for your
step tablet which is rarely the case, you wouldn't be sure they behave
exactly the same way mostly because of there (probably) different response
to UV, if you make digital negatives, then I would suggest making a step
tablet the same way you intend to make your negative since this way you can
establish a direct relationship with what you see on screen (pixel values),
your negative and your print if you are using a scanner of course. Creating
an adjustment curve using this pixel values instead of densities is
pratically child play. A traditional step tablet would give you more work to
establish this same relationship.

Regards
Yves

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, March 31, 2006 1:02 AM
Subject: Re: gloy for tricolor on yupo?

>
> 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 13:23:23 2006