[pure-silver] Re: RC print dryer (was prints curling)

For the same kind of money you could get a Mohr, or perhaps other brand, of 
print processor.  Dry to dry in 2 minutes. You'd be limited to the size of the 
processor you get of course.



________________________________
From: John Bower <john@xxxxxxxxxxxxxxxxx>
To: pure-silver@xxxxxxxxxxxxx
Sent: Friday, April 24, 2009 7:34:43 AM
Subject: [pure-silver] RC print dryer (was prints curling)

I tend to have a lot of ventilation air moving through my darkroom, so low 
humidity could easily be the culprit. I don't have room to hang up my prints, 
but I have considered an Ilford 1250 infrared print dryer. For two reasons: 1) 
keeping prints flat, and 2) because it will increase d-max. However, I've read 
that it's a high-maintenance piece of equipment (as well as very large and 
heavy). Does anyone know of a similar dryer by another manufacturer? Thanks.

John Bower




On Apr 23, 2009, at 11:53 PM, Richard Knoppow wrote:

> 
> ----- Original Message ----- From: "John Bower" <john@xxxxxxxxxxxxxxxxx>
> To: "Silver Silver" <pure-silver@xxxxxxxxxxxxx>
> Sent: Thursday, April 23, 2009 7:35 AM
> Subject: [pure-silver] rc prints curling
> 
> 
>> Ever since I started printing (~8 years ago) my RC prints (Ilford  
>> Multigrade IV, pearl finish) develop a slight curl when drying (the  corners 
>> turn up, so the print has a slight bowl shape). After rinsing  for 3-4 
>> minutes, I squeegee them on each side, then place them on  fiberglass 
>> screens, and they always have the curl when dry. Why? Shouldn't RC prints 
>> dry perfectly flat?
>> John Bower
>> 
>     Both prints and films curl for the same reason: the emulsion shrinks at a 
> different rate than the support. Since RC support can not absorb water it is 
> the emulsion side that is causing the curl. When gelatin dries it shrinks and 
> expands again when it absorbs water from the air. I've found that mostly RC 
> prints dry pretty flat but when it gets really dry here (was 7% two days ago) 
> they curl so strongly that they will peel right off mounts if spray-on 
> adhesive is used. Dry mount won't peel off but can actually curl cardboard 
> mounts. I suppose the application of a humectant such as glycerine might help 
> but anti print curling solutions are supposed to be a bad idea from the 
> archival standpoint (can support fungus growth). I suspect steaming the 
> emulsion side would take the curl out, at least temporarily.
>     Fiber also curls because the emulsion shrinks faster than the support. 
> The idea of drying on screens emulsion side down is to keep some moisture in 
> the emulsion while allowing the support side to dry. I've never found this to 
> work particularly well. Blotter books have a layer of non-absorbent material 
> on one side again to prevent the emulsion side from drying out too fast. The 
> only method I've ever found that gives me reasonably flat fiber prints is to 
> treat them in a dry mounting press. That works well but should not be 
> necessary for RC prints.
>     BTW I also dry RC by hanging it like film.
> 
> --
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
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