Re: Image formation in gum

On Dec 16, 2005, at 8:08 AM, Jack Brubaker wrote:

> Tom,
>
> Isolating the possible reflectance of the glass and background might
> tell a
> lot. I am wondering if the process is very different than I always
> assumed.
> I think most of us thought that the light would diminish in strength
> as it
> diminish the gum layer. Some of the light being absorbed by the
> pigment and
> the gum. But maybe that is a minor effect and most of the light is
> reaching
> the base. If so the reflection of the light could create strong
> exposure at
> the back of the layer. If these ideas are combined, the light is
> diminishing
> as it penetrates, and it is reflecting off the base, there could be
> more
> hardening happening at both the front and back of the gum than in the
> middle
> of the layer. I'm not sure what that has to do with the reversal
> effect but
> it could explain a lot of confusing things we see commonly in gum
> printing.

> For instance how can a hardened layer float off an image layer.

Exactly. I know you guys think that's what's happening here, that the
hardened gum layer is somehow splitting itself vertically into a
hardened gum layer that floats off and a hardened gum layer that stays
on the glass and forms an image. But it's not my experience that gum
works that way, and besides, I don't see any reason to suppose that's
what's happening in this particular case.
Katharine.
   
Received on Fri Dec 16 11:25:16 2005