Re: Light Sensitivity of FAO, Carbon Arc Exposure etc.

hi Ray

Bill William wrote:

>OK
>Here are some more beginners questions to go the still
>unanswered-ones below:
>
>How are the light sensitive Iron salts for use in alt.
>Photo. (eg. FAO) best purchased, sold and stored?
>
> In White or Brown Glass?
>
> In White or Brown plastic bottles?
>
>
>
when you buy the chemicals I assume the packing they come in is
adequate. would not leave it out in the sun though.
B&S FO from pgi comes in white plastic.

>The main question here is...
>Is the light sensitivity of Iron processes reversible?
>
>
>
do not know, this is a two step process, one light+ferric=ferrous then
ferrous+metal and image formation, what do you mean by reversible ?

>Unanswered Old Questions:
>1.
>I have an almost unused carbon arc lamp boxed up in
>another room... can this be used and if so, would the
>results be comparable to other more common forms of UV
>lighting for Iron Process exposures?
>
>
>
1. best might be to just try to make a print.

2. find the spectral info sheet on the lamp, might be enough to google
on the product number & name. Highest sensitivity for ferric oxalate is
prossibly @ 365 nm, the paper I gave you last time contain some graphs
with the spectral absorbency pattern for ferric oxalate, have a look.

>2.
>Can the hexa-hydrate FAO also be used?
>
>
>
I have not used this but, ( I am guessing here) as you mix this out in
water the hydrate is irrelevant, only thing to take into account is that
you might have to recalculate the weights in the recipe. at least for
pt/pd keep a 2 : 1 molar ratio fe to metal.

>4.
>How do Ferric Ammonium Oxalate and Ferric Ammonium Citrate
>compare in activity?
>
>

depends on which process you use it for. the AmmFerrCit is used in
cyanotype, the FAO in Pt/Pd POP-style. In Pt/Pd the FAO will (very)
probably have a much higher sensitivity/performance than if you used the
citrate.

have a look at Abney&Clarke which could be downloaded from bostic&S
website, it contains a list comparing sensitivity of various ferric
complexes, I did a test on this with about the same results. (see page
21 in that green paper i gave you this spring.)

>Can they be used interchangeably?
>
>
>
not really. although I have not compared this particular performance.

>Thank you in advance,
>
>Ray
>
>
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>
>
>
>
halvor
Received on Tue Aug 17 20:17:25 2004