the ratio....15/7/24..... ratio of what? What chemicals are you using? A&
B type Platinum and Ferric Oxalate?
The exposures sound extremely long—bad chemistry? Way too much restrainer?
Negatives that you could watch carbon arc welding through?
Could your Ferric Oxalate be old? Has it been mixed for more than 6 months
or so?
You can speed up PT/PD by using less restrainer and increasing humidity for a
start...
I would think you are reaching reciprocity failure with such long exposure
times....
What is wrong with your light source? Does it need to be rewired? I would
fix that first then take a look at your chemistry...
are you using a standard step wedge in your exposure tests?
With the depletion of the Ozone layer I would think you would be getting
enough UV there to roast prairie dogs or rock chucks....
Mark Nelson
Precision Digital Negatives
In a message dated 3/9/04 12:25:35 PM, richsul@earthlink.net writes:
> >So I have started to print platinum, and it has been ticking me off. our
> >light source is not getting full power to the bulbs, so their output is
> >really low and unpredictable. my exposure times were well over three
> >hours,(my test strip was for an hour and it was a good 3 stops under
> >exposed) in the light source and 45 minutes outside in bright sunshine,
> >about a stop and a half under exposed. is there just no uv radiation in
> >MT??? my ratio was 15/7/24 should i change this for digi negs? is there
> >any way to speed up the emulsion of a platinum print? my tests from non
> >silver for a type 55 neg was 1.5 hour exposure, why are they sooooo long?
> i
> >am going to continue running some tests because i really want to get this
> to
> >work, but any advice would be greatly appreciated. ---dave
>
Received on Tue Mar 9 13:06:51 2004
This archive was generated by hypermail 2.1.8 : 04/01/04-02:02:05 PM Z CST