I've cut and pasted from the Pure-Silver list a Freestyle Photo response to the question of Yellowing Kentona:
[pure-silver] Fwd: Kentona, response from Freestyle Photo
From: Elias Roustom <elroustom@xxxxxxxxx>
Date: Fri, 5 Dec 2008 08:19:30 -0500
Hello Group, here's some useful information from our favorite b&w supplier:
From: "Oliver Tan" <oliver@xxxxxxxxxxxxxxxxxx>
Date: December 4, 2008 6:35:32 PM EST
Subject: RE: Kentona, Sent By: Elias Roustom (22.214.171.124)
We know of this problem before. The reason why there are some stains on
the paper is because Kentmere removed the cadmium that it originally
came with. Basically, this changed the whole composition of the emulsion. A solution to correct this problem is to change developer and use distilled water. The less this paper soaks in chemicals, the better it will be for the paper also. If you are using a metol based developer, try switching to a phenidone base developer or vice versa. Water also plays a part in this chemical reaction that's why distilled water is
Europe is trying to ban cadmium because it is a known carcinogenic.
Manufacturers, not only in photography, but also in paints and others
reformulated their ingredients to remove cadmium.
Hope this clears up everything. Let us know if you need more information
or have any more questions.
Retail Asst. Manager
Freestyle Photographic Supplies
From: elroustom@xxxxxxxxx [mailto:elroustom@xxxxxxxxx]
Sent: Thursday, December 04, 2008 12:54 PM
Subject: Kentona, Sent By: Elias Roustom (126.96.36.199)
Are you at Freestyle aware of the problems people are having printing on Kentona? I've uploaded two prints onto Flickr to show the staining that
is happening. http://www.flickr.com/photos/elroustom/3082943772/
I've found a photo.net thread where others are seeing the same thing.
Maybe between you and Kentmere you can figure it out. Unfortunately I
have about 12 sheets left, and they're useless...