Acid in Sensitizer ( was puzzled by paper )

[R Shaffer]

I thought I would start a new thread as I am curious about this and did not want to hyjack John's thread.

I would be curious to find out what the advantages or disadvantages may be to adding acid to the sensitizer.

From reading Dick Stevens "Making Kallitypes, The definitive Guide", he suggests adding acid to the sensitizer can help clear the print. ( I remembered something about precipitate & ph, but I had it backwards )

Now Stevens relates the insoluble ferric hydroxide ( red/yellow stain ) as being controlled by having sufficient acid (tartaric acid) in the developer ( or sensitizer ) preventing hydrolysis.

Then Mike Ware states
"To minimize this loss of image the Kallitype process employs alkaline-buffered developers of high pH, e.g. Borax. Alas, these create a new problem, because they cause hydrolysis of the excess iron(III) in the sensitizer and the deposition of insoluble ferric hydroxide in the image, which ultimately causes it to fade."

When I use a borax/rochelle salt developer I can see the bright yellow stain, however it seems to completely clear easily in 3% citric acid. When I use sodium citrate developer, I see a very light red stain, however it seems to completely clear as well in 3% citric acid.

Like I said before, I had a very difficult time getting prints that I had double coated to clear. Would the acid in the sensitizer help?

If the print is cleared, is all the ferric hydroxide gone? Or is there still a potential to fade?

If I tone in palladium or gold, then does all this become moot as there is no more silver to degrade.

PS: Sorry about the lengthy post

 

[sanking]

If the print is cleared, is all the ferric hydroxide gone? Or is there still a potential to fade?

If I tone in palladium or gold, then does all this become moot as there is no more silver to degrade.

PS: Sorry about the lengthy post

When the print is cleared most of the ferric hydroxide is gone, but probably not all of it. I believe there is a diminishing return in clearing so that it is virtually impossible to remove all of the iron hydroxide but with proper clearing you should be able to get rid of enough of it to make the print stable.

Also, don't confuse fogging with staining. Although it does not happen in my work some people have complained that they get fogging when working with the lights on. If you have fogging it will obviously never clear.

Any iron left in the print could endanger its long term stability. This is true of pallaidum and platinum printing as well as toned kallitypes and vandykes.

About the stain with double coating, the most probable cause is that you are using too much sensitizer, assuming your other procedures are being carrier out correctly. Reduce the total amount of solution used for each coating by about 20-25% and you will probably see a reduction in the stain. However, be aware that there is a fine line between obtaining maximum Dmax and staining.

Sandy King

 

[R Shaffer]

Thanks Sandy,

The kallitypes I made a couple years ago still look great, so I'm thinking I got them well cleared and cleaned.

I have had issues from time to time getting prints to clear and I had not thought about fogging. I do use a 60W tungsten light in my dimroom, so maybe some tests with a yellow bug light are in order.

Next time I try double coating I'll dilute the sensitizer a bit more and see if that helps.