U of S | Mailing List Archive | alt-photo-process-l | Re: How many gum layers (Re: ferri sesquichlorati)

Re: How many gum layers (Re: ferri sesquichlorati)

Katharine, thanks for input .. are still "absorbing" this ...

One last (maybe) gum question..

I have seen two approaches for building up the tone scale.. One is to use a
constant pigment concentration and on subsequent layers reduce the exposure

The other to use a constant exposure time but to increase pigment
concentration for each layer (which with my test reduces sensitivity

Is one method more usual than the other, I originally only knew the first
one.., Is one method best, or is this just a matter of purpose ... Comments
any one ?

On 10/24/06 12:02 AM, "Katharine Thayer" <kthayer@pacifier.com> wrote:

> Halvor, I'm coming late here; you've just posted your revisiion, but
> since I've already written this I'll go ahead and send it:
>   I agree that how many layers depends  on the thickness of the
> layers (BTW the same gum emulsion goes on thicker on nonabsorbent
> surfaces than paper IME) and on the substrate (my experience has been
> that I can print fewer layers on nonabsorbent substrates rather than
> more, but that may also be partly related to my experience  that the
> layers are thicker on the nonabsorbent substrate).
> As to the relief effect Keith described,  I think it's also related
> to the paper you use how many layers it takes to get this effect.
> With Arches bright white,  if I'm printing a fairly high-contrast
> image (very thick areas of gum interspersed with very thin areas of
> gum) I get this effect even with one layer of gum. If you look at the
> print from the back, you see the image in relief in the paper, that's
> how pronounced the relief effect is.  I thought at first it was a
> differential shrinking of the paper around the gum and assumed I
> could avoid the effect by preshrinking the paper, which I don't
> ordinarily do, but found to my surprise that preshrunk paper does the
> same thing; it's apparently a relief thing not a shrinking thing
> that's going on.
> By the way,  a couple of years ago I took one of these warped prints
> and had it dry-mounted to flatten it, and announced that solution
> here, but I don't think I'd do that to a finished print again,
> because it seems like it would mash down the relief.  People seem to
> be fine about the relief effect, in fact they like it, so I've
> decided not to worry about it.  Like I said, it's only noticeable
> with a print that's fairly high contrast.
> Katharine