Re: Ziatype: how many coatings?

From: Jeffrey D. Mathias ^lt;[email protected]>
Date: 10/10/04-08:56:18 PM Z
Message-id: <4169F652.1000009@att.net>

Loris Medici wrote:
> ...
> I have sodium citrate - will that work as developer?

Yes. With FO sensitizers it usually gives a flatter look but a more
neutral color. With AFO sensitizers, it doesn't seem to make as much of
a difference, especially when the AFO contributes to that same slight
flatness and cooler color. Note that very warm color prints can be made
with AFO and low RH (relative humidity), but it is rather difficult (and
perhaps too difficult) to get a bluish or very cool color with FO.

> ...Your e-guide is great. But the detail is intimidating I must admit.
> Asking this before looking your site: I have used a 40% ammonium
> iron(III) oxalate solution. Do you think this is strong enough?

Yes. This can be found in Chapter 15 in the section called
"Verification of Optimized Formulas (Threshold for AFO solutions)".
Again, remember that these things are dependent on the paper used.
40%AFO solution should do the job. The section also outlines a
procedure to determine the threshold for those wishing to find out the
specifics for their own situation. Remember to use the proper solution
strength for the metal solution. The strengths used through the guide
assume a one-to-one mixture of sensitizer solution and metal solution.
If solutions stronger than the threshold are used, the material is
wasted and in some cases surplus metal may "bleed" and even stain a print.

Important also is the section on coverage in the coating chapter.

>...
> I use digital negatives. So I will make test for every combination I
> plan to use. I'm trying with a straight AFO + LiPdCl mixture for the
> moment. Later will make experiments by dialing in Sodium Tungstate and
> Gold Chloride...

As to digital negatives, keep in mind that unless printed with 16-bit
depth, there will be posterization that will not present the fine subtle
tonal discriminations Pt/Pd is capable of producing. If committed to
digital negatives, images should be chosen that work within these
restrictions.

> Another question (to both of you):
> The print doesn't clear well. I used two tablespoons of citric acid to
> 2lt water - it cleared the whites to some extent but there's still a
> veil in the highlights. What can I do to effectively clear Ziatype?

There are several other clearing agents and as may be expected, this is
paper dependent. Check out the Clearing Study in Chapter 15 to perhaps
get some ideas. Also check the Clearing Test. I have even found that
with some papers and proper additives to the coating mixture, plain
water can clear completely in a short time. A note about water: the
water used for clearing solutions can be problematic if it contains a
significant amount of iron.

-- 
Jeffrey D. Mathias
http://home.att.net/~jeffrey.d.mathias/
Received on Sun Oct 10 21:04:06 2004

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