[alt-photo] Re: Alternative sensitiser

[Kees Brandenburg]

Thanks Peter!

Is the pineapple enzyme in the juice of the fresh fruit? Just press it?

The problem with gum and ferric ammonium citrate for me was that the exposed emulsion floated of the paper in the peroxide bath. The peroxide doesn't have the time to do it's hardening I think. It seems to work though with the hydrolized gelatin and maybe even better with casein as your prints show.

Kees
 

On 19 apr 2010, at 00:54, Peter Friderichsen wrote:

> Kees,
> 
> To mildly hydrolyse the gelatin, you can either acidify, or alkalize it, then heat it for a limited time, or use an enzyme like that from fresh pineapple. They all seem to result in different surface properties of the gelatin which now is liquid at room temperature and whose prints produced from such, can be developed at room temperature.  M. Carey Lea first made something like this which he called meta-gelatine.
> 
> You can keep this for some time at room temperature if you add the right preservative, but like any gelatin in solution, it will slowly auto-hydrolyse (much slower if kept cold), and the result will be weak prints. At room temperature, I find it works well for about 6 weeks. Gum arabic as you know seems to last much longer if preserved.
> 
> 
> Peter Friedrichsen