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