Re: a versatile surfactant that kills bubbles; OT Jobo

After working in darkrooms with pals who use the Jobo, using their Jobos and
hearing all the idiosyncracies with using them, my personal conclusion is
that they're a big waste of time and money.

Side by side, my friend and I did negatives, he with his Jobo and my with
the tray and a green light, I got more done in good shape that he with the
f!@#$ Jobo with less mess and less effort.

For bubbles, I use a pre wash and make sure the negative drips water free
and clean across the surface before putting it into the developer. So many
experiences with pinholes on negatives in my life.

S. Shapiro
----- Original Message -----
Subject: Re: a versatile surfactant that kills bubbles

Ryuji:
For sure I'm not knowledgeable about all those surfactant formulae and
habits,
but, a long time ago, in a JOBO newsletter, one person said the secret to
spreading
liquid emulsion was to add a few drops of good quality heavy cream to the
batch being
used for coating. I presumed it had something to do with emulsified fats or
something t
o do with casein that allowed the material to spread smoothly.
I have always wondered if the final emulsion could go 'bad' and sour after
the final
processing but maybe it all washes out in the end.
Jack Fulton

On Jan 16, 2005, at 1:38 AM, Ryuji Suzuki wrote:

It's nothing major but it may be of great practical use for some people.

I've been using Triton X-100 for many uses without thinking but a
while ago I was so frustrated. It gives only ok spread of emulsion
when coating unless bubbling amount is used. I've tried some defoamers
but too much defoamer is a quick way to get unevenly coated
spots. Anionic surfactants of sulfonate types (e.g. Triton X-200)
seems to be very effective in improving spread of emulsion, but I
found these way too bubbly for brush coating.

Here's the silver bullet I found. Tergitol L-62. This is a polyether
polyol (nonionic) of MW 2500. It has faintly sweet smell and almost
zero toxicity. It has a decent wetting activity AND defoaming effect,
especially at temp of 30 to 50C. Wetting could be further improved by
addition of another surfactant like Triton X-100 (though I'd rather
use Tergitol TMN-6 if I were shopping for surfactant today).

It doesn't do anything special but it reduced the level of frustration
at a couple of steps in silver gelatin emulsion making as well as
coating in my practice. In particular, bromide emulsion worked well
with unsized Fabriano Artistico Extra White HP. I never thought it
would work like that easily before. It's a WD-40 of darkroom work.
Received on Sun Jan 16 17:06:11 2005