[alt-photo] Re: Alternative sensitiser

[Peter Friedrichsen]

Hi Kees,

I found the concentrated pinapple enzyme at a health store (in 
capsule form). It is called Bromelain. . The concentrated enzyme is 
very powerful- perhaps 30 mg/30 g gelatine and a couple of hours at 
RT is sufficient (the warmer it is -but not hot, the faster it acts) 
- timing and temperature is everything here. Too much and the gelatin 
gets very watery and the prints are thin. Too little and the gelatin 
thickens up too quickly upon coating. Once it is sufficiently thin, 
you do have to boil the gelatin for a half minute or so to deactivate 
the enzyme.  You likely will have to do this a few times before you 
get it the way you want. It is tricky until you develop a system. 
Plenty of notes needed as you experiment.

You may try it from the fresh juice of the flesh-not processed 
because the enzymes are destroyed. I haven't done this so I don't 
know how much or how long, and there is the acidity that you may have 
to eliminate afterwards.

Of course your methods may create results that differ from mine, and 
perhaps you will discover useful things that I have not, and 
hopefully we can a learn a little more.

I look forward to hearing about your results.

Peter Friedrichsen

At 04:51 AM 04/19/2010, you wrote:
>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
>
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