[Alt-photo] Dichromate-Waste

Laura V laura at lavatop.com
Tue Mar 15 09:43:00 UTC 2016


Not sure I understand - why neutralize before taking to the chemical 
waste facility? Don't they do that?

Laura

On 3/15/16 9:14 AM, Kees Brandenburg via Alt-photo-process-list wrote:
> Nice find! Foodgrade ascorbic acid (E300) can be found very easily through food supply wholesalers and is not expensive. And you need not much for neutralizing your first wash water before bringing it it to the chemical waste depot.
>
> Let’s say you make some prints with a 60ml total volume of (1+) gum and 10% dichromate. Then there wil be 3 gram pure dichromate in this mix. A part plays its role during exposure and the rest will dissolve (mostly) in the first wash.
> To neutralize all of this 3 gram there will be 5,3 grams ascorbic acid needed, according to the paper’s calculations. And you suggested to double that to 10 gram.
>
> Udo did you also test the folowing?
> It would be nice know what will happen when using a pre-ascorbin-acidified first wash. Let’s say when using  3 liter water in a tray with 30 gram of ascorbic acid. This is a 1% solution. This 3 liter will be capable of neutralizing 9 gram of dichromate with ease. This is the equivalent af all the dichromate in 180ml 1+1 gum/10% dichromate. That’s a lot of emulsion to print.
>
> Would this method influence the image formation? Will it form a (green) stain in the paper?
>
> In my workflow I always use two trays. A smaller one for the first 3-5 minute, where most of the unused dichromate will dissolve. And a bigger one for the next phase where the pigment comes loose. First tray is neuatralized with metabisulfite and goes to the chemical waste depot, second down the drain.
>
> Kees
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