Originally Posted by Stan. L-B
The normal chemistry for the kallitype sensitizer on this side of the pond is also ferric oxalate and silver nitrate, more specifically a 1:1 mixture of a 20% solution of ferric oxalate with a 10% solution of silver nitrate.
What Phil and Don are talking about is adding small amount of potassium dichromate to the developer, in this case sodium citrate, to control contrast. When you use sodium citrate as the developer it is possible to adjust the amount of dichromate in the developer from virtually none to as much a about 16ml of a 5% solution per liter of developer to match negatives with DRs that range from about 1.3 to as much as 2.0 or slightly higher.
As for the Fabriano water color papers none of these have worked well for me in recent years with kallitype. Both artistico and uno give prints of rather low Dmax. Dmax can be increased slightly with an oxalic acid soak of the Fabriano papers but it remains unacceptably low in my estimation even with this procedure.
There are a number of other developers that one can use with kallitype, including potassium oxalate which is my second choice behind sodium citrate. Assuming that you will tone your kallitypes, as one surely should if permanence is of any concern, the choice of developer is not very important since the final image will take on the tone of the toning metal, regardless of which developer you use.