[alt-photo] Re: Don't take the brown FAC!

[Alberto Novo]

Trevor,
brown and green ferric ammonium citrate have different Fe/NH4/Cit. ratio and 
pH (Clerc reports two different formulas, though they are usually sold 
declaring two different Fe percentage ranges), so the best is to calibrate 
again your curve. 

Alberto
www.grupponamias.com
www.alternativephotography.com/articles/art102.html 


> Hey gang, 
> 
> Well, after a long wait, I finally have chemistry for gum and 
> cyanotype...or so I think. I opened my FAC and discovered that it looked 
> VERY brown. After mixing according to the traditional cyanotype in 
> alternativephotography.com, it doesn't have that iridescence I remember, 
> and the dried emulsion is brown. I haven't exposed one yet because my sun 
> decided to hide for the rest of the day's useful light. In the Unblinking 
> Eye, there's mention that the brown FAC is less sensitive and has a lower 
> tonal range than the green. Should I be making an effort to reduce 
> contrast? Any suggestions as to how I might alter the solutions to 
> compensate? Something tells me I'm going to have to really dial in a 
> specific curve for this ride. 
> 
> Trevor