View Full Version : "Rapid fixer" v.s. plain old "fixer"

Calamity Jane
1-Mar-2005, 07:21
There's so many REALLY sharp people on this forum somebody can probably answer my question:

What's the difference (chemically) between plain old "fixer" and "rapid fix"?

I've been sitting here impatiently waiting for some plain old hardening fixer to arrive so I can try my Rockland tintype process - their data says that "rapid fix" will wash out the image - but nobody around here stocks simple fixer, only rapid fix, so I am waiting for my order from Porters to make it's way thru Canada Customs, and waiting, and waiting, and waiting . . . (drums fingers on table)

I have gallons of rapid fixer but not a drop of simple old fashioned fixer. . . .

Gem Singer
1-Mar-2005, 07:30
"Plain old fixer" is sodium thiosulfate, otherwise known as "hypo".

Rapid Fixer is ammonium thiosulfate.

Two different chemicals that accomplish the same result. However, Rapid Fixer does it faster.

1-Mar-2005, 07:36
You can get hypo from fotochem. You may even be able to find it locally. A different form of sodium thiosulfate is used in swimming pools so if you have a large pool supplier nearby you may be able to get it.

Don't know what Porter is charging you but for next time:


Or watch:


Same people. They used to have 10lb bags along with 10lb bags of sodium sulfite.

Usually shipping from Montreal is very fast.

N Dhananjay
1-Mar-2005, 08:54
As mentioned above, plain fixer is sodium thiosulfite, also called sodium hyposulfite or hypo. Rapid fixers are based on ammonium thiosulfite. Both of them have the ability to dissolve silver halide from the emulsion, but rapid fixers are much more active/powerful. Fixers do have the ability to attack image silver also, although this takes time and concentration. Finally, there appears to be a difference in the washing rates - although there are two sides to this issue. Plain fixers are typically just this side of neutral (slightly alkaline) which makes it supposedly easier to wash the fixer out of the paper. Rapid fixers are often acidic (acidic formulations were required for hardeners to work, and it is possible to formulate an alkaline rapid fixer - TF3 in the developing cookbook, for example). The acidic nature supposedly closes the pores in the paper making it harder to wash out residual fix. On the other hand, Ilford has tests demonstrating that the reduced time spent in the rapid fixer (because rapid fixer is faster acting than plain fixer), reduces the adsorption and thus reduces wash times. Of course, if you use an alkaline rapid fixer like TF3, you get both benefits - less time required in fixer and the benefits of an alkaline environment.

In practical terms, rapid fixers have a faint ammonia odor, which plain fixers do not. Many folks have commented about the inability of plain fixers to deal with iodide, which makes rapid fixers probably preferable for modern film emulsions, which are iodide rich. Most paper emulsions are based on silver chloride and bromide, so both fixers will probably work well. Some folks prefer the plain variety to reduce the risk of attacking image silver, especially the high values in a print (alternative processes generally psecify plain fixer for this reason), while some people prefer alkaline rapid fixers for the supposed wash time benefits.

Cheers, DJ
Cheers, DJ

Jay DeFehr
1-Mar-2005, 12:17
There's rapid fix, and then there's Superfix! Superfix is Ron Mowery's ammonium thiosulfate-based fixer. It is an acid fixer, with a target Ph of 6.3-6.7, but I use it with a water bath between dev and fix, and haven't seen any of the pinholeing often associated with carbonate developers and acid fixes, even though my Rapid Universal developer uses quite a lot of carbonate. With this dev/fix combo, I get fully developed and fixed negs in under 3min.! I love it.

Jim Ewins
1-Mar-2005, 12:38
Calamity, you may contact The Formulary in Montana about their TF4 Archival Rapid Fixer (no hardener)- it's a must for pyro as well. I've been using it for film and paper. No stop bath. No problems bleaching and toning. 1800 922 5255 or photoformulary.com, Jim

Roger Scott
1-Mar-2005, 14:06
I've been researching the same issue but for a different reason. The smell from rapid fixer is getting up my nose. :-) As others have mentioned the difference is in which thiosulphate is used. Normal fixer is also quite easy to make and if you don't need the hardener and use a stop and rinse before fixing you only really need the sodium thiosulphate and sodium sulphite which makes it cheap. The usual extras are acetic acid which makes the fixer acidic along with sodium metaborate (Kodalk/Borax). Finally potassium alum is added as a hardener but if you don't want a hardener you don't need this which also means you don't require an acidic fixer. As previously mentioned if you use a stop bath and rinse to ensure no acid from the stop goes into the fixer and you don't use hardener you don't need the acid or metaborate either. It does however take a bit longer to work than the rapid (ammonium thiosulphate) fixers you've been using. Hope that makes some sense.


Calamity Jane
1-Mar-2005, 16:45
I KNEW I'd get lots of really good information on this forum!

Plain old fixer is cheap like grass clippings in summer, it's just that nobody here stocks it. So, if I have to order something in, I might as well order fixer. (I just happened to need some other stuff from Porters so I added it to the order. Even my local pro shop can get it, just that they don't stock it.)

Thanks for the great chemistry lesson!

(BTW: When I relocate my darkroom this summer, I am going to install an exhaust hood. I had been away from B&W processing for years and, when I started doing 4x5, I found I had a couple of old partial bottles of stop bath so I threw them together and used them - the fumes just about knocked me over. I thought "I don't remember this stuff being this bad!" Later I ran across the instructions for stop bath "mix 60:1" - Oh, that's why the fumes were so bad! It pays to read the directions :-) Did you know that undiluted stop bath works REALLY good? BAW HAW HA HA!)

1-Mar-2005, 17:35
Once you have the hypo you can make any hypo based fixer you want. From plain old hypo with nothing added. To TF-2 that is a nice alkaline fixer. To the various acid fixers.

With a reasonable number of chemicals you can make most developers,fixers and anything else you might want. In the amount you want. Plus most of it is fairly simple.

3-Mar-2005, 22:41
someone correct me if i'm wrong. It's been ages since I've used Kodak rapid fix. But doesn't it come in two parts? and if you leave out the hardener shouldn't you have what you want? The reason I mention this is because it is readily available at any photo supply. If you're in a hurry that is

Calamity Jane
4-Mar-2005, 06:11
I don't believe the hardener is the problem. Rockland say that RAPID fixer will wash out the image, so it is apparently the amonia that is the problem (which makes sense because they also suggest household cleanser to strip the emulsion from a plate).