RE: Pyrocat-HD for alt printing?

OK, several things.

About exposure. Exposure in alt printing as in
silver gelatin printing is based on shadow
density, and the stain of a Pyrocat-HD negative
is proportional and there is very little of it in
the shadows. So if your exposures are very long
with Pyrocat-HD it is because you are
over-exposing your film because there should be
very little B+F. In alt printing as in regular
silver gelatin printing, exposure is based on the
shadow density, while contrast is based on
highlight density which you control through paper
grade filter or with some process control, say
Na2 or dichromate in palladium printing. In
short, a well-exposed and developed Pyrocat-HD
negative should not take much longer to print
than a well-exposed negative developed in a
non-staining developer.

Shelf life. The shelf life of the Pyrocat-HD
stock solution is about a year in partially full
containers. When it turns brown, discard it and
mix or buy fresh solution. The metol variant will
last somewhat longer. It gives slightly greater
sharpness but less effective film speed. However,
unless you buy Pyrocat-HD in very large quantity
chances are you will use it up long before Stock
A goes bad. Contamination is nearly always the
cause of early death of Stock A and this usually
happens while mixing the working solution. If
even a minute quantity of Stock B gets into Stock
A it will cause it to go bad within a few weeks.

Finally, if you really want a very long-lived
Pyrocat-HD Stock A solution, there is the option
of mixing it in propylene glycol. You must heat
the glycol in a water bath to around 150-75
degrees F, then add the chemicals in regular
order, stirring each until completely dissolved.
This solution does not oxidize and like stock
HC-110 solution will last for years and years.

Sandy

>Hi loris,
>
>Never used it, sorry, but I seem to recall it's
>more stable than Phenidone, but that also
>depends on the other stuff in the stock..Sandy,
>where are you..;-)..
>
>Best,
>
>Cor
>
>> -----Original Message-----
>> From: Loris Medici [mailto:loris_medici@mynet.com]
>> Sent: dinsdag 16 augustus 2005 14:38
>> To: alt-photo-process-l@sask.usask.ca
>> Subject: RE: Pyrocat-HD for alt printing?
>>
>>
>> Hi Cor,
>>
>> What about the shelf life of the metol variant?
>>
>> TIA,
>> Loris.
>>
>> -----Original Message-----
>> From: Breukel, C. (HKG) [mailto:C.Breukel@lumc.nl]
>> Sent: 16 Ag˜ustos 2005 Salž 15:30
>> To: alt-photo-process-l@sask.usask.ca
>> Subject: RE: Pyrocat-HD for alt printing?
>>
>>
>> Hi Susan,
>>
>> I know and experienced the oxydation of the PyrocatHD stock
>> "A", OTOH I
>> last week used succesfully a stock made in in December 2004.
>>
>> The "good" thing is that you can at least see that your stock is dead,
>> compair that to Xtol..;-)..
>>
>> I stored the stock in a clear glass bottle around which I have wrapped
>> aluminium foil.
>>
>> I woder if switching the Phenidone with DimezoneS would help in
>> increasing storage life (DimezonS is a much more stable variant of
>> Phenidone).
>>
>> Best,
>>
>> Cor
>>
>>
Received on Tue Aug 16 07:32:48 2005