Re: First Carbon

On Mon, 16 Oct 2000, Joao Ribeiro wrote:

> Well, the lamp is a kind of street lamp. I can find 2 types here, one is white
> with some sort of coating that absorbs the UV emission, the other is
> transparent, that last one is the one I use.

I kind of thought that might be the case. I have no direct experience
with them. In either case, the bulb is usually constructed with an
secondary, UV absorbing, glass jacket. The packaging that comes with
these units usually says not to operate the light if the outer jacket is
broken. My guess is that this eliminates a good amount of the UV light
generated.

> The lamp (single unit) is above
> the printing frame at a distance of 45 cm.

OK, you are about 16 cm's closer than I am. You don't have problems with
heating?

> I used paper waxed neg., dmin
> equivalent to Stouffer's step 3.

My experience is that paper negatives are not as fast as film based
negatives so that will increase exposure times.

> I usually give my gum prints 6 minutes, that's why I started with
> this. But my gum is 1:1 with NH4 dichro, so I guess it is much faster,
> besides it is never black (at least not soooo black).

I haven't printed any gum since this past January or so, but I seem to
remember using shorter exposures for gum.

> BTW, the tissue, dry, is beautiful, very deep black. The gelatin I am
> using it 200 bloom.

Sounds good!

> > Under exposure would also be consistent with the no image failure mode.
>
> What does it mean?

If you had gotten some exposure, you would probably have seen something
that looked like an image before it washed off of the substrate. If this
never happened, the gelatin all dissolved at the same rate. That pretty
much indicates that little if any hardening occurred.

> > Did you wash the exposed tissue in cold water for about 1 minute before
> > putting it into the tray with the final support paper? This wash step
> > removes the soluble dichromate, and softens the gelatin layer.
>
> No, I didn't.

You probably do want to do this. We had a discussion on the list about
the criticality of this step some time back, and how this could affect the
adherence of the gelatin image to the support tissue. It is possible that
your image didn't stick, but I'd kind of expect that you would at least
have seen some sort of image form before it all separated from the
substrate.

> > I assume that you never saw anything resembling an image as the tissue
> > developed out?
>
> No image at all, but most of the tissue dissolved easily, but part was
> well, I don't know the name in English, but like milk, when it cools
> and forms a thicker part at the top.Some of my tissue was like this, a
> very thin "nata" as we say in Portuguese

In English we would say that cream forms on the surface of milk when it
cools and the milk fat separates. Something with this texture is said to
have a creamy consistency. This also sounds like partial hardening.

> I will. I sensitized all the tissue, can I still use them?Thanks for the help

That depends on how long ago you sensitized it, and how you stored it.
It will slowly harden on its own with time which can cause problems with
contrast, etc.. However, I've used sensitized tissue that has set for as
much as a week. If not too old it should be OK for gross exposure tests.

- Wayde
  (wallen@lug.boulder.co.us)
Received on Mon Oct 16 11:44:43 2000