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 08:30:04 2005