Has anyone experienced their New Cyanotype sensitizer going bad after 1 month?
I have been mixing my new cyanotype chemistry using bulk chemicals from the Photographer's Formulary. Twice now, after one month of use, I will go to use my sensitizer and find my solution has gone from an olive-yellow colour to a dark blue. It will typically print OK for one more session, and then I will go to print and my prints will have lost all dmax, and have very little contrast. My sensitizer is stored in a 100ml amber bottle, inside a box, inside another box, in a mostly dark room (sometimes the door to the darkroom is left open and some fluorescent light gets in -- i work in a shared studio). I only take it out under a 15 watt bulb.
I follow Mike Ware's instructions pretty precisely: Under a 15 watt yellow bulb, I bring 20ml of distilled water up to ~70°C on my hotplate, and then dissolve my 10g of potassium ferricyanide. Keeping this solution hot, I dissolve 30g of ferric ammonium oxalate into 30ml of distilled water that has been heated to 50°C. I then add 0.5 ml of 25% ammonium dichromate solution to the ferric ammonium oxalate solution, and then add my potassium ferricyanide to this. I let the solution cool for an hour until it is at room temp, then filter off my solution using a coffee filter.
My yield is normally low - usually from 33ml to 45.5ml. I add this up to 100ml to make my final sensitizer.
What is going on? Has anyone else experienced this?
I have been mixing my new cyanotype chemistry using bulk chemicals from the Photographer's Formulary. Twice now, after one month of use, I will go to use my sensitizer and find my solution has gone from an olive-yellow colour to a dark blue. It will typically print OK for one more session, and then I will go to print and my prints will have lost all dmax, and have very little contrast. My sensitizer is stored in a 100ml amber bottle, inside a box, inside another box, in a mostly dark room (sometimes the door to the darkroom is left open and some fluorescent light gets in -- i work in a shared studio). I only take it out under a 15 watt bulb.
I follow Mike Ware's instructions pretty precisely: Under a 15 watt yellow bulb, I bring 20ml of distilled water up to ~70°C on my hotplate, and then dissolve my 10g of potassium ferricyanide. Keeping this solution hot, I dissolve 30g of ferric ammonium oxalate into 30ml of distilled water that has been heated to 50°C. I then add 0.5 ml of 25% ammonium dichromate solution to the ferric ammonium oxalate solution, and then add my potassium ferricyanide to this. I let the solution cool for an hour until it is at room temp, then filter off my solution using a coffee filter.
My yield is normally low - usually from 33ml to 45.5ml. I add this up to 100ml to make my final sensitizer.
What is going on? Has anyone else experienced this?
