[alt-photo] Re: ***NOW HEAR (READ?) THIS: COT IS AVAILABLE! was Daniel Smith paper chart!

[Loris Medici]

Could be that Fotospeed stock was a little bit old or their raw
materials were contaminated. Hear this: About 1.5 year ago, I ordered
few kg's of ammonium iron(III) citrate (for friends/students and
myself) from Sigma Aldrich (actually Fluka), "purum" quality and guess
what? It had a little iron(II) impurity that is enough to turn mixed
A+B cyanotype sensitizer into blue!!! I had to devise a method for
purifying it (a couple of tests to determine the minimum amnt. of
hydrogen peroxide that has to be added into the A solution in order to
eliminate iron(II) completely...), further confusing students.
Unfortunately, "stuff" happens... ;) Hope you'll be luckier next time!

Regards,
Loris.


24 Şubat 2012 20:08 tarihinde Christina Anderson <zphoto at montana.net> yazdı:
> ...
> For example, if it wasn't for Mike Ware's help about this Ware's formula clearing issue I am having, I would have assumed either Buxton paper or Ware's formula was a b---ch to clear when, in fact, it is actually more probable from his information it is contaminated chemistry. I would never think freshly bought chemistry was contaminated.