Re: Antifoam agent

From: Marek Matusz <marekmatusz@hotmail.com>
Subject: Antifoam agent
Date: Wed, 26 Apr 2006 02:29:54 +0000

> I remember that Ryuji mentioned a kremer antifoam. I am not sure
> that it is a typical silicone antifoam, they do not give any detail.

Well, what makes you say that? I have this product and it works the
same as other typical silicone oil based defoamers. It defoams very
well, particularly in combination with a small amount of nonionic
surfactant. You can also use hydrophobic silica and other fine
particles. These are also very effective, particularly in combination
with silicone oil. Kremer Defoamer contains some solid particles and I
think it's this kind of combination defoamer (very common).

There are other agents that don't make emulsion in aquaous phase (just
homogeneous mix or dispersion). There are some barely soluble
polymers that have defoaming function. But their defoaming power is
much more mild compared to silicone oil emulsions. If you say Kremer
Defoamer isn't strong enough, I don't think these agents would work
for you.

Regarding bubbles caused during small tank development, I am also
annoyed by them. Apparently, some modern films use a lot of anionic
surfactant to aid coating, and they foam a lot. Fujifilm Acros is
probably one of the worst... (tho the emulsion is one of the
best). People bring me negatives with strange marks, asking me what
they can do to prevent them... I now know without looking... the film
is most likely Acros. Presoaking removes much of the surfactant. I
attach Paterson tank to the temperature-regularted water line and
"wash" the film for a few minutes before developing them! I've also
thought about adding defoaming agent, but I wasn't brave enough to use
dimethylpolysiloxanes (silicone oil defoamer), so I thought about
using defoaming polymer... but if I were to add yet another agent to
my formula, I also wanted to have some useful photographic property,
so a couple of candidate polymers are being tested. At least one of
them reduces overall nonimage fog without affecting development or
shadow detail, so I'm pretty excited to pursue this line of approach.
Received on Wed Apr 26 00:38:43 2006