helloRecord Rapid and Portriga were not identical papers; Portriga had a warmer tone and both were in 2 or 3 surfaces glossy, mat and grainy
and 1to5 grades for RR and 1 to 3 for PR.I still have some boxes in the freezer of Portriga Rapid from the 1985-1990 and it is still working and without fog. But even at that time the emulsion wath different from the originally first RR and PR from de 1970'.
Daniel Bouzard www.danielbouzard.com Le 28/01/11 07:59, Richard Knoppow a écrit :
----- Original Message ----- From: "Mike Kirwan" <mkirwan@xxxxxxxxxxx> To: <pure-silver@xxxxxxxxxxxxx> Sent: Thursday, January 27, 2011 6:50 PM Subject: [pure-silver] Re: Oh How I Miss This PaperI will have to look at the old ads. RR was advertised in the British Journal Almanac, I think and it seems to me it was identical to something sold by Agfa under a different name here. I think the chemical was a cadmium compound. I one of the members of this list is Dave Valvo who designed papers for Kodak. I am not sure he still follows it. He would know definitely what had to be changed because of environmental regulations. Whatever was done it seems to affected the shelf life of raw stock and also seems to have affected warm tone emulsions more than neutral or cold tone ones. Emulsion making as described in some of the older books is highly simplified. Its a very complex process with many additives. The chemistry is way beyond me. A lot of the popular wisdom about it is either out of date or was never correct. For instance, the amount of silver in the emulsion has little or nothing to do with the way the final image looks. I think Kodak had the most advanced emulsion making technology in the world but not always the best looking papers although they had the most consistent emulsions and most uniform surfaces. Anyone who has had to deal with the frilling and cockeling of Agfa papers knows what I mean.Portiga was a different paper, nice, but not the same as Record Rapid.I still have some Portiga in my collection, has a different surface than RR. If my memory serves me correctly, one of the reasons for the demise of these papers was some of the chemicals in the emulsion, I believe that both RR and Portriga had a Cadmium component; which was also in some of the famous andlong lamented Kodak papers :( Mike-- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.
============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.