> Judy
>
> since your personal solution worked fine at home, but cacked on you at
> school, what is the possibility of contamination in the water you used, or
> the containers and mixing instruments you used.
> I'm no master chemist, but some variable changed between your front door and
> the school, no?
> Risa
My thoughts have travelled along those lines too, but nothing really fits.
Apparently my pound of FAC, which gave a light green solution in my
distilled water at home, made a dark brown-green solution in the distilled
water at school -- in the same cup or jar that formerly mixed light green
solution. What comes to mind is contaminated "distilled" water. We once
did get tap water (certified by the chem department) some years ago in a
sealed jug bought with the label "Distilled." (This is Brooklyn.)
HOWEVER, brown or not, my pound of FAC seems to be working OK in vandyke
(which we're doing now).
I thought the problem with lot #3 might just be funny water at school, so
I brought a pound home and mixed a dose with my own distilled water --
expecting to see light green after all. No. Lot #3 came out dark
brownish green here, too.
Philip Jackson suggests dark green-brown isn't serious. I'll mix up a
batch of cyanotype with lot #3 before end of semester & then will know
more. If it prints OK, then this is a semi-false alarm. But it's still
puzzling.
Cheers,
Judy