For the last few days, I have been making comparisons of the sharpness of hand coated prints using my own emulsions. This should also be true using Liquid Light and other similar products.
Since I have only done Blade, dip and brush, I cannot comment exactly on the spray coating other than what is published.
This work is based on making defninition chart exposures of negative and positive images (which reveal bloom and fill in).
Some of the papers tested include Strathmore, Lanaquarelle, Cranes, COT320, and a host of others including 3 grades of Baryta and RC.
All are acceptable and yield some spectacular results, espeically the textured Strathmore Watercolor which is simply beyond description for some pictures (but is not very sharp). I think Denise Ross has said it best. These images can be stunning and repeat what some of the old textured surfaces gave us.
I encourage you all to try making your own coatings on some of the textured papers out there. Please be aware that you must coat more emulsion on cold pressed papers than on hot pressed papers and you must 'learn' how to do this. It is like learning how to paint a picture with extra steps.
I think I'm finding that the developer makes a difference, too. I'll be more sure of that after a couple more runs of tests. My results this week are up here: http://dwrphotos.com/blog/EmulsionResearch.htm#Current and one date back (Oct 30 - Nov 3)
I'm with PE in encouraging more folks to work on this. I just finished reading "Memoirs of a Photochemist", by Fritz Wentzel, and I was struck by how the past and future keep circling around each other. In many ways, APUG'ers are recreating the excitement and investigative energy of those early photographers. So much knowledge has been lost and even small machine shops and mechanical skills are getting harder to access. We're pioneers and historians at the same time. Very cool.
Excuse me for asking what seems to me to be obvious. If we are going to engage in hand coating our printing materials, why not go to a known process and go with pt-pd? Or even Kallitype toned in Pt which seems to be indistinguishable from pt-pd.
The collectors of photographic art will buy pt-pd ten to one over silver.
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Art is a step from what is obvious and well-known toward what is arcane and concealed.
A knownprocess? Where's the fun in that? And, if money if the motivation, photography may not be the very best profession to be in. Far more important is this: they are different works of art, as different as watercolor is from oil. Color, texture, appearance, best negatives for the process - all different and in my opinion, viva la.
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Certainly true that each has it's own advantages. Pt-pd does have the capability of altering contrast contrary to popular belief. The advantages of Pt-pd are longer tonal scale. The disadvantage, to some, is lower dmax than silver.
The fun in doing something that is known is not having to reinvent the wheel at each and every turn. I have lived the better part of my time on this earth and would rather spend it making good photographs. But to each his/her own.
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Art is a step from what is obvious and well-known toward what is arcane and concealed.
Donald, I've often wondered about that. It seems to me that a longer tonal scale and a lower dmax are contradictory, as a longer tonal scale to me requires a higher dmax.
In any event, if you make your own emulsion you can control the tonal scale rather than take what the manufacturer thinks you should have.
You are correct about contrast, I had forgotten that, but can you devise a range over 4 grades? You can with silver. IDK personally if you have that range with Pt/Pd.
And, you can keep the emulsion for quite a long time, as well as the coated paper or film. Can you do this for Pt/Pd? I really don't know.
I'll probably think of more reasons, but cost comes to mind as well. Silver nitrate costs a LOT less than either Pt or Pd salts.
Yes, cost is a factor...no doubt about that. But I think that is offset by the higher esteem in which Pt-pd prints are held by most.
I think that because of the higher cost and perhaps the greater degree of experience/knowledge that pt-pd printers usually possess, that most know how to expose and process the camera negative so that it exhibits repeatable and foreknown density scale characteristics.
The one characteristic that hand coating silver would offer is that the print would exhibit more of the pt-pd characteristics so far as the emulsion residing within the paper rather than sitting on the baryta layer.
So far as the requirement of a long tonal scale requiring a high dmax, I don't follow your reasoning on this. The difference in the materials is such that the dmax (whether it is 1.65 or 2.10) is not related to the distribution over which the rest of the tonal scale is represented.
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Art is a step from what is obvious and well-known toward what is arcane and concealed.
Donald, the tone scale is the total length of the sensitometric curve from where the curve starts to rise above dmin (toe) to where it levels off at dmax (shoulder). If the dmax is lowered, then the shoulder is closer to the toe and the tone scale is shorter. That is the definition I learned at EK with all of the diagrams and technobabble removed.
Sharpness and quality of handcoated prints 
Linear Mode
