Blistering of emulsion

[Gene_Laughter]

Over the weekend I processed some B/W paper for bromoil: Kentmere Art Document Pro - test coating #1333 (BTW - this run has a super coating layer). When processing for bromoil one enlarges, develops the print, stop bath, fix with hypo crystals, 30 minute wash and then throughly air dry. Next comes bleaching / tanning. Eight minute bleach in copper sulphate, pot. bromide and Pot. bichromate formula. Wash for 10 minutes, fix with hypo crystals and wash for 20 to 30 minutes. Air dry.

After the post bleach wash the emulsion of the Art Document Pro prints all had numerous blisters on the surface.

Over the years I have processed many hundreds of prints for bromoil. All in the same manner. This is the first time that I have ever experienced emulsion blistering with any paper. Processed in the very same batch were a few prints on Agfa MCC 118 (leftover stock), a few on Fotoimpex paper and a few on Kentmere Fineprint. Same chemistry. Same routine. Only the Art Doc Pro blistered. I contacted Kentmere, but received no explanation that makes any sense to me.

Any ideas on why an emulsion would blister? :confused:

 

[Photo Engineer]

Gene;

I'm assuming that these are supposed to be normally hardened papers.

Emulsions blister when the hardener is left out, or hardening is reversed somehow.

The only common hardener that can be reversed is chrome alum. I don't know of any others that can be easily reversed, but some agents can swell an emulsion and cause abrasion.

So, it sounds as if either the hardener was left out, or chrome alum was used and was undone by the process in spite of the tanning.

There are a lot of other possible problems such as a problem in the supercoat, a problem in the subbing (baryta) and etc, all of which can lead to some sort of blistering.

Mainly there are two types. One is a large blister the size of a dime or a quarter and is filled with water or air. These break and smear while drying and leave strands of emulsion like flaking skin. The other is a series of tiny blisters like chicken pox on a human. These usually dry down to leave a fish skin scaly type of surface on the paper. They are both from poor hardening.

PE