I don't think that the Arches Plantine has an Alkaline buffer but from Christines latest posting you may have the answer to my problem. I didn't use acetic acid in the wash so I will try that, as well as I will try Jim Patterson's suggestion of citric acid.
Quote from Christina Z. Anderson email
The WASH of dilute acetic acid is to remove the ferricyande toner out of the paper. If ferricyanide is not removed from the paper, it auto- decomposes after some time to iron ferricyanide, the blue stain. If your tap water has iron, use distilled water. Also a 1% citric acid wash may work better than the acetic acid wash.
On 20-Jan-09, at 12:29 AM, Alberto Novo wrote:
... It still could be the clearing time and I am just having trouble clearing the Iron out of this paper. I was also wondering if I have Iron in the wash water. I live in a large city and have been using tap water for the final wash.It could be also some iron left in the paper due to its alkaline buffer.