Ferric oxolate problems?

[stefano_ber]

another problem with Kallitype. Very dense black dots that come out during or after development. It about 10 days that they come out and then after drying they disappear from the surface(the quality is not good however), but can be seen transparently. Basically they are inside the paper. So I thought it was ferric oxolate which I know is very delicate. I also tried to filter it, but nothing. Anyone have any idea how to fix this? If is this the problem, why is it so short life? I've always kept it in the fridge! I have attached a dry example and a detail in transparency.
Thank you
Stefano

 

[aldus_manutius]

Can you describe, specifically, your steps of processing? Which paper are you using? My first reaction to seeing these was bad clearing, but that's without knowing how you proceed.

 

[stefano_ber]

this problem I have with different papers and the dots appear already during the development and then increase the intensity during the clarification. It seems to me more a problem related to Ferric Oxalate than anything else, also because up to 10 days ago I had no problem! but I would like to have a confirmation.
More precisely, as soon as I put the paper just exposed in the development appear immediately a lot of grain, then it decreases over time, but something remains, even if not yet black. Then during the clarification I do in a double bath with 3% acidified distilled water they become more evident and darken.
Thank you anyway!

 

[iakustov]

Can you see these dots just after exposure, before development?

 

[stefano_ber]

No, especially after development. it seems to depend on the brush not totally clean. I usually always clean it well, but using a sponge brush it is possible that something is retained anyway.
do you have any other suggestions?
thanks

 

[TheMissingLink]

Perhaps the solution is too saturated and what you see are tiny cristals. I prepare my own oxalate and have to let the solution rest some time plus filtering several times before using...

Ho.

 

[Andrew O'Neill]

I have seen this when I used a bad batch of Arches Platine a few years ago, and with a bad batch of ferric oxalate, or when the stock solution is used after its best before date. I only get FO from Bostick and Sullivan now, as it is of a high grade, and mixes very easily into water.