[alt-photo] Re: pd/pt coating solutions

[David Ashcraft]

OK, I'll do some testing and see.
Thanks,
David


On Mar 30, 2011, at 12:32 PM, Eric Neilsen wrote:

> David, I am saying don't add it at all. And  now that you are  
> talking about
> digital negs, a very small amount may be needed. Just as with  
> photoshop
> workflows where one needs to know the whole thing, hardware type and
> software versions, before offering up to much "do it this way", it is
> important to know others entire process to put the mixture into  
> perspective.
>
>
> Potassium Chlorate does indeed make images have contrast, but even  
> in slight
> amounts can produce pronounced grain. IS that a problem? Not for  
> some, and
> that's visually speaking. You may have been told you MUST add a  
> little to
> keep the fogged highlights down. That may be or not.
>
> Nomenclature 101 - Not everyone prints with the B&S chemicals, nor  
> Dick
> Arentz method or... so Ferric Oxalate can come in a powder or liquid  
> form.
> It can be home made in either type. I make a liquid. I have gone  
> from Pot
> Chlorate, H2O2, tried Dichromates, (sodium, potassium, ammonium) in  
> separate
> solutions and at different concentrations in the developer. I  
> currently use
> the platinic acid method that B&S users might refer to as Na2. All the
> methods that restrain the highlights can be looked at for you  
> preferred
> workflow. Several can be made as separate solutions and added to the  
> coating
> solution just prior to coating the paper. Some can be added to the  
> ferric
> prior to the drop count time and you just end up with more solutions  
> to add.
>
>
> If you are using solution two, in the B&S system, then that is where  
> the
> chlorate comes in and the chlorate has more effect on some solutions  
> than
> others. The balance is in PD and PT for color and contrast. The  
> additional
> contrast changes come from gold and how it reacts with pd, pt and  
> any other
> parts; say lithium. Each new concentration and balance of pd, to pt to
> sodium, to ammonium, to lithium changes the retainers that one might  
> use.
>
> Any change in your pt, pd ratio, as well as a change in humidity and  
> any
> additional additives like gold will benefit changes.  The changes to  
> be made
> will be depend on what you want to see.
>
> Eric Neilsen
>