Yellowing paper in lith printing

[Dali]

Hi there,

I am currently printing a short serie of negatives with Kentmere Kentona (most recent version I guess) and Moersch Easylith developer.

So far, everything was fine until last Saturday.

This day, I did some experiments to raise the contrast for one negative: I diluted the developer more than usual (1+44 instead of 1+30) and reduced the exposure of the paper. Also, I heated the developer to around 80-85° F. Developement time was about 12 minutes.

In terms of contrast, results were not significantly better than before (?) but I clearly noticed that the paper base (including the margins) turned yellow instead of staying more or kess white as usual (which goes against a contrast increase)... Where this yellowing coming from? Too warm developer? Another cause?

Thanks!

 

[ajsikel]

Generally, to increase latent colourization the temp of developer is increased significantly..so, that might be a hint.

 

[koraks]

Hydroquinone in the absence of sulfite or with very low sulfite developers as in a lith developer will oxidize and stain. The longer development and the higher the temperature, the more stain there will be. Beyond a certain point, the stain becomes general and not linked to silver image density. Basically, you're seeing oxidized hydroquinone on your paper.
So to prevent this in a lith scenario, reduce development time and/or temperature.