Re: Ziatype: the result of my second test.

Loris Medici wrote:
> ...
> As you can clearly see, the density of the digital negative is not
> enough to print paper white. I will have to use some kind of contrast
> agent - probably ammonium dichromate. What is your suggestions about AD?
> I plan to start by adding 1 drop of 25% AD to 25 drops of coating
> solution - is that too much to start, should I start with a milder
> addition?

Whoa!
That's about a hundred times too much.
You can get an idea about contrast agents from my e-guide in the section
  on Preparing Stock Solutions in Chapter 6.

> Another point: After the second test (which was exposed 2:30 - the first
> one was exposed 1:30) I still think dmax is a little bit on the low side.

I suggest that you are way off base on this dmax thing.
First, the materials are going to give more density than usable in the
print.
Second, the important darkest density is how it looks in the final print
of an actual image.
Trird, densitometer readings and density numbers are not the same and
not as accurate as how it looks to your eye.
Forth, the film densities must also be set properly for the printing
process and materials.

What is more important is finding what I term the maximum black. This
is influenced by the film, exposure and processing and the print
process, materials, and technique. The printing time is determined by
the exposure necessary to produce the maximum black. The negative
should be made to accommodate a range of densities that go from the
densities that are the threshold necessary to produce the Zone I and
Zone 0 in the print (Zone 0 will be a notable density on the film. Zone
0 in the print will not be the maximum the materials are capable of
producing.) to the density necessary to produce a pure white (paper
base) in the print. The Zone in which that pure white occurs may differ
and is certainly influenced by process and materials. Then what happens
to the curve between these densities can be manipulated.

There is more on this in the section on building negatives in my
e-guide. In particular look at the stack method.

But yes, your initial concern is to get a good black from your printing
process. To do this one must be clean, precise and consistent with
their materials, conditions, methods and techniques. Reading densities
will not achieve these things; it takes practice and experience.
Training the eye to read negatives and prints is valuable.
Practicing is valuable.

-- 
Jeffrey D. Mathias
http://home.att.net/~jeffrey.d.mathias/