Hello Michael!
Sorry for the late response.
1 What is the difference between the metal solutions for methodology 1 and 2? I assume it was the mix of Pt. and Pd. but the descriptors for both are 50-50. I understand that these pre-mixed solutions, when combined with different humidity levels, produce prints with different hues (from warm to neutral to cool).
I will back track a bit first. IJM packages M-W Pt/Pd solutions in two ways:
either as a single, pre-mixed solution, ready to coat onto paper, and referred to as a sensitizer;
or as a set of solutions that should be mixed before coating.
The M-W solutions, in other words, have a long shelf life even after being mixed together.
To avoid some confusion, I have recommended that all mixed solutions that are ready to be coated onto paper be referred to as sensitizers and the separate components be referred to as solutions - such as ammonium ferric oxalate, ammonium tetrachloroplatinate(II) and ammonium tetrachloropalladate(II).
Now to your question. The ammonium ferric oxalate solution may be prepared with just that compound (Methodology 1), or with an addition of ammonium nitrate (Methodology 2). [I prefer calling these just Fe Method 1, and Fe Method 2, or even more conveniently, Fe1 and Fe2, respectively.]
The differences between each are:[/floatl]
1. Color: Fe1 generally prints much warmer than Fe2. These differences are most dramatic the the coated paper is hydrated in atmospheres between 30% and 50% RH / 20°C (approximately). The differences narrow with higher hydration levels, but you will find that Fe2 can render very neutral to cool tones around 80% RH, depending somewhat on the Pt and Pd content of the sensitizer.
2. Contrast: Fe1 is slightly more contrast than Fe2, and the same hydration dynamics noted in #1 apply here.
3. Paper: Some papers will render much smoother tones with Fe2. Much of this has to do with the interactions between hydration (ammonium nitrate is a humectant, and increases the sensitizers ability to retain water molecules) and paper content.
The “50-50” part of the question: The sensitizers are actually a combination of:
Fe1 or Fe2 + ammonium tetrachloroplatinate(II) + ammonium tetrachloropalladate(II)
For convenience again, I prefer to use the shorthand, “Pt” and “Pd” for the precious metal solutions above. So, Methodology 1, 50-50 actually means that the sensitizer is mixed with 100 parts of fe plus 50 parts of Pt plus 50 parts of Pd. I feel it is simpler to describe this as a set of ration, where Fe1:Pt:Pd is 2:1:1.
The printing-out M-W process combines the iron and precious metals in equal ratios. In other words, the amount of Fe needs to be equal to the total amount of Pt and/or Pd to make an effective final sensitizer.
2 Malde and Ware only have one formula for producing ammonium iron(III) oxalate (or so I’ve been able to find), so what is the difference (chemically) between the two iron solutions offered by inkjetmall?
Actually, you are right. There is just one formula for preparing ammonium ferric oxalate (AKA ammonium iron(III) oxalate). What we have above is a modified formula, with added ammonium nitrate serving as a humectant. The chemical difference then is that Fe1 is a 60% w/v ammonium ferric oxalate solution while Fe2 is 60% w/v ammonium ferric oxalate + 34% w/v ammonium nitrate. The Pt and Pd content, in the sensitizer, is the same for either preparation.
Here are the two formulae:
Ammonium ferric oxalate: Method 1
To make a final volume of 50 ml, 60% w/v ammonium ferric oxalate
Ammonium ferric oxalate, (NH4)3[Fe(C204)3].3H2O, 30 g
Distilled or purified water at 122°F / 50°C, 50 ml
Instructions
- Weigh out 30.0 g of the ammonium ferric oxalate and set it aside.
- Measure 30 ml of warm distilled water (104–122°F / 40–50°C) contained in a 100 ml measuring beaker,
- Add the ammonium ferric oxalate to this, while stirring with a clean glass rod until all the crystals have dissolved. The result is a clear bright green liquid. This should take no more than about 10 minutes.
- Make up to a final volume of 50 ml with distilled water.
- Filter the solution into its brown storage bottle.
- Label the bottle.
- If, after about 24 hours, a few white needle-like crystals (probably of ammonium oxalate) have appeared, re-filter the solution to remove them.
- In your notes, also include the source and batch number of the ammonium ferric oxalate.
Ammonium ferric oxalate + ammonium nitrate: Method 2
To make a final volume of 50 ml, 60% w/v ammonium ferric oxalate + 34% w/v ammonium nitrate
Ammonium ferric oxalate, (NH4)3[Fe(C204)3].3H2O, 30 g
Ammonium nitrate, NH4NO3, 17 g
Distilled or purified water at 122°F / 50°C, 50 ml
Instructions
- Weigh out 30.0 g of the ammonium ferric oxalate and set it aside.
- Weigh out 17.0 g of ammonium nitrate and set it aside.
- Measure 30 ml of warm distilled water (104–122°F / 40–50°C) contained in a 100 ml measuring beaker.
- Add the ammonium nitrate to the distilled water and stir with a clean glass rod until all the crystals have dissolved.
- Add the ammonium ferric oxalate to this. Stir until all the crystals have dissolved. The result is a clear bright green liquid. This should take no more than about 10 minutes.
- The presence of a few crystals can be ignored. Make up to a volume of 50 ml with distilled water, stirring well, and set aside in a very dark place, to cool to room temperature, for about 1–2 hours.
- Filter the solution into its brown storage bottle.
- Label the bottle.
- In your notes, also include the source and batch number of the ammonium ferric oxalate and ammonium nitrate.
These solutions should be made up at least 24 hours before use, and stored in the dark at room temperature. They will keep under these conditions for at least a year.
All of the above is going to be listed, with illustrations, in the forthcoming book, Platinotype: Making Photographs in Platinum and Palladium with the Contemporary Printing-out Process [preorder here :)]
3 Closely related to question 2 is if I have the ammonium salts of Pd. and Pt. (as described by Malde and Ware) then which iron solution from IJM would one use (as opposed to ammonium iron(III) oxalate as described by Malde and Ware)?
So, I hope I have answered this question above. But just to be sure:
You can use either. OR, if you wish, both Fe1 and Fe2 in any ration, so long as the total amount of Fe is equal to the total amount of Pt/Pd. The net effect is an astonishing sliding scale of color options. All of this can become a bit mind-boggling. So, here’s a simpler approach. Prepare one bottle of Fe1:Pt:Pd, and another of Fe2:Pt:Pd, both at 2:1:1 ratios. Then, just before coating a sheet of paper, you can mix these two together in any desired combination to arrive at a print color that meets your vision! I.e. a print coated with:
Just Fe1:Pt:Pd, hydrated at 52% will have a warm red-brown tone
One part Fe1:Pt:Pd plus one part Fe2:Pt:Pd, hydrated at 52% will have a slightly warm
Just Fe2:Pt:Pd, hydrated at 52% will have a neutral tone
I hope all of this helps! Thanks, and happy printing!
Pradip
