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Sulfuric (milky) Fixer

haryanto

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I always get milky fixer when try to add potasium alum to sodium thiosulfate in F6a Ansel Fixer
the formula is:
Sodium thlosulphate (hypo) 240.0 grams
Sodium sulphite (anhydrous) 15.grams
Acetic acid 48 ml
Sodium Metaborate 15 grams
Potassium alum 15.grams
Water to make 1000 C.c.
is that any harm to prints?
How to get rid the milky

I know there's opinions about not to use hardener but I still want to use it

thanks a bunch
 
The formula looks fine. The milkiness is not good though. The suspended particles can cause problems with film images and the surface gloss of prints among other problems such as decreased fixing or hardening power.

The order you give is good, but how much water do you start with? You should start with about 750 ml at about 100 F, then add the first 2 ingredients. When dissolved, add the acid and then the alum. The metaborate should be added slowly while checking pH. The pH should be at about 4.5, no lower, and no higher than 5.5. It should end at about 3.5 - 4.5.

Is the acetic acid glacial or 28%? This is important.

PE
 
water 750 ml at first
yes Acetic acid 28%

Thanks PE
 
Make sure that the first 2 ingredients are dissolved before adding acid. The early addition of acid can cause sulfurization of the hypo if the pH falls too fast.

If the pH is too high, then Aluminum Hydroxide will precipitate.

Hope things work out for you.

PE
 
the ingredient always dissolved before adding the next, but I'll try to watch the PH

thanks PE

Haryanto
 
haryanto said:
I always get milky fixer when try to add potasium alum
to sodium thiosulfate in F6a Ansel Fixer

How to get rid the milky
Click to expand...

Milky, likely sulfur. Sulfur dissolves in a solution
of sulfite to form thiosulfate. I've not run any tests.
Adding additional sulfite may be a harmless way of
clearing the fix.

The ph of any of the ingredients listed can vary;
eg, the alum may vary from 3 to 3.5. I'd likely
make up the 750 ml with all the more alkaline
ingredients, dilute the acid in most of the
needed remaining water then slowly
with stirring mix the two.

Is that the method you've used? Dan
 
Yes Dan, the PH is the accurate way to find the problem, PH more than 4.5 when add Pot Alum will make it milky, I've found my Glacial Acetic acid seems not 99.5% so when I make it up to 28% it's not 28%
I cant measure the percentage of my Acetic acid,
I had to add Acetic Acid till to 200ml to reach my fixer PH 4
 

First a correction. In effect sulfur will dissolve in
a sulfite solution. Actually the sulfite is oxidized
by the sulfur into the thiosulfate.

So which is it to be ph 4 or ph 4.5? How do you
measure ph?

If you've an accurate scale and can measure an
exact amount of the acid the determination of
the acid's specific gravity will be easy. From
that the acids strength can be found. Goes
for dilutions as well. Dan
 
PH 4 is after all ingredients except the P alum dissolved
I measured PH with PH indicator paper merck, not quite accurate but I notice that in PH 5 I got milky when add the P alum
do you mean that to dissolves the sulfur I had to add sulfite more? or should I just adjust my acetic acid?

thanks a lot Dan

Haryanto
 
haryanto said:
PH 4 is after all ingredients except the P alum dissolved
Do you mean that to dissolves the sulfur I had to add sulfite
more? or should I just adjust my acetic acid? Haryanto
Click to expand...

Remember, the Alum's ph may be as low as 3. If you are
at ph 4 then add alum you'll be below ph 4. Adding more
sulfite may clear that milky fix you've mixed. Test
a portion. Add and stir in a little at a time. Dan
 
Ok Dan, I'll try
thanks again

haryanto
 
Last edited by a moderator:
I know that you expressed a desire to use the hardener, but you really don't need it for prints. I used to use half the amount of hardner, and then abandoned it completely. You should try it without it, I think that you will like it.
 
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