Slavich Unibrom coating / emulsion features.

In the last few days I have started making some prints with Slavich Unibrom paper. My pack of 24x30cm grade 2 shows a clean white base with no apparent issues, however my pack of grade 3 paper does appear to show issues. I used both ID-14 and Fotospeed PD-5 developers.



The above scan shows a variable mottling or fogging effect. I've altered the contrast curve on the scan to show the effect more clearly.



This scan from another sheet of the Slavich Unibrom grade 3 paper without additional curve altering. This sheet shows a consistent grey mottling or fogging effect with some of the emulsion coating starting to remove itself from the paper base. This latter issue may be related to soaking time.

Three causes might be: 1. light fogging of paper at some point, 2. coating / emulsion defect, 3. chemical issue in my darkroom.

During the darkroom sessions I have used the Slavich paper in I also used ILFORD Galerie, Kentmere Bromide, Adox Variotone Premium etc. without the Slavich mottling.

Tom.

Tom, that's very interesting. I've been using Unibrom for well over a year and haven't had any such problems. However, its been a year since I bought my current stock. Was your's purchased recently?

Freestyle is quite good about replacing products distributed by them that may have defects.

Slavich Unibrom G3 emulsion number: 5004. Process before: August 2010, so it would appear to be fresh paper. G2 emulsion number: 5050. Process before: August 2010.

Tom.

I was just printing last night and found "stripes" on some sheets while lith printing and horribly inconsistent print to print. The package I have may have similar problems as yours. I finally gave up. May have to exchange it....):

Mark Fisher said:

I was just printing last night and found "stripes" on some sheets while lith printing and horribly inconsistent print to print. The package I have may have similar problems as yours. I finally gave up. May have to exchange it....):

Click to expand...

Have you tried conventional development, do you know the emulsion number?

The grade 2 paper I have used so far seems to work fine.

Tom.

I'm using Grade 2, lot 5050. I don't really expect consistency out of this paper. It seems to be worse as the developer becomes exhausted. Most papers lith better as the developer becomes exhausted. I think I'll just print with Slavich near the beginning of a session and use other papers later.

Well, there are also paper defects in FB paper that can cause this type of effect, but you do not mention the paper type (I assume FB) and the scans are not clear enough. There are also emulsion and process defects.

Basically, fine particles of contaminants in paper or emulsion can cause a black speckle that is called "pepper grain". It can be from tiny dots all the way up to the size of a peppercorn.

PE

PE,

The second scan does accurately show the problem, however I acknowledge the first scan is not as clear. This mottling effect across the 5 or 6 sheets processed is inconsistent, nearly all around the edges with a clean white paper for the most part to the almost uniform grey mottling of the second image.

The paper is fibre base.

Tom.

Tom;

My first guess then would be a paper defect in the baryta, and the sescond would be an emulsion defect in which the grains were allowed to clump. This is presuming no bad keeping or processing problems.

PE