[pure-silver] Re: shamefully off topic
- From: Charlie Thorsten <charlie_thorsten@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 21 May 2007 01:20:00 -0700 (PDT)
--- Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
> Cibachrome AKA Ilfochrome, is, perhaps, best
> described as
> a direct positive process rather than a reversal
> process. It
> is based on the idea that certain dyes can be made
> colorless
> by the reaction products of development. Ciba/Ilfo
> chrome is
> black when unexposed. The development bleaches out
> the image
> where its light struck. I suppose this is a bit
> nit-picking
> but it is a different process based on a different
> principal
> than reversal. In a reversal process the image is
> first
> developed to a negative. Instead of fixing the image
> and
> removing the unused silver halide, the remaining
> halide is
> used to produce the final positive image. For B&W,
> the
> original silver image is removed by a bleach which
> does not
> affect the halide. The halide is then exposed to
> strong
> light or treated in a chemical which has the same
> effect.
> The emulsion is then developed leaving a positive
> image.
> Color processes are a bit different, the original
> silver
> negative image does not have to be removed. Rather
> the first
> development is carried out in a developer which does
> not
> generate dye so that there is just the negative
> silver
> image. Then the film is either exposed to light or
> to a
> fogging chemical, as above, and developed again,
> this time
> in a developer which produces the dye image. The dye
> image
> is, of course, positive. The last step is to remove
> the
> silver images, both positive and negative, leaving
> only the
> positive dye image behind. There is a little more to
> than
> this but not much.
Wow you're bringing me back to my Type R printing
days. What a beautiful process. The machine was
a pain to keep clean and maintained (nine tanks
versus four for RA4), but I loved the results.
I have many of them still hanging on my walls!
*sigh*
But the great thing about B&W is I can do it
occasionally as a hobby. Get out the trays a
couple times a month, rinse them out afterwards,
no problem. I don't have to worry about the
R3 bleach-fix tanks building up sulfer anymore...
AAAHHHHHHH!!!!!!!!!!! Hehehehe...nevermind. :)
-Charlie
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