Ammonium Thiosulfate floating debris

lensmagic · Jul 1, 2008

I have been buying PF ammonium thiosulfate in ten pound quantities. I use it for fixing films and paper. The most recent ammonium thiosulfate does not fully dissolve. Please see attached photo of the debris floating on the surface. The ammonium thiosulfate is mixed just as it was previously, in filtered tap water at room temperature. The debris seems to have no effect on the effectiveness of the ammonium thiosulfate as a fixer, and it rinses off of paper readily. I worry that it will become embedded in film, however. Can I filter this residue out?? If yes, what kind of filter should I use: paper (coffee filter)? metal?

Photo Engineer · Jul 1, 2008

You can probably filter the residue out. Use a paint filter or better. Notify the Formulary. Bud has strict quality criteria!

PE

jim appleyard · Jul 1, 2008

I take it you are ordering the thio in powder form? If so, how long are you waiting for it to dissolve? Sometimes powders take several hours to dissolve.

lensmagic · Jul 1, 2008

I forgot to add the the debris leaves a "ring around the bathtub" on mixing vessels and trays. Yes, this ammonium thiosulfate is in powder, or perhaps more correctly, crystal form. Earlier examples of the chemical went into solution almost instantly. This version doesn't go into solution even after hours.

lensmagic · Jul 1, 2008

Photo Engineer said:
You can probably filter the residue out. Use a paint filter or better. Notify the Formulary. Bud has strict quality criteria!

PE

World's dumbest question: what is a paint filter?

Photo Engineer · Jul 2, 2008

lensmagic said:
World's dumbest question: what is a paint filter?

Yes, but anyhow you can buy them at any hardware store in the US. They are fine filters that are used to remove debris from paint.

They are also used by physicians to detect kidney stones.

PE

jim appleyard · Jul 2, 2008

lensmagic said:
I forgot to add the the debris leaves a "ring around the bathtub" on mixing vessels and trays. Yes, this ammonium thiosulfate is in powder, or perhaps more correctly, crystal form. Earlier examples of the chemical went into solution almost instantly. This version doesn't go into solution even after hours.

Give PF a call, see what they have to say. They're customer service is very good.

Formulary/Bud Wilson · Jul 2, 2008

The powdered Ammonium Thiosulfate requires +-120degrees F to disolve. Also this product may have a reaction with iron compounds within your water supply, if on a well or Chlorine if on a city water system. Your filter system should have the ability to deal with either of those.
The product also has only come from one lot # so it is the same material that you have gotten from us before.
If you want to use your filtered tap water and dissolve at room temp, just simply filter, as mentioned before thru a coffee filter or paint filter and use normally.
Thanks for bringing this to our attention and we will run a test of this today.
If we find a problem we will post on this thread.
Thanxs
Bud

MurrayMinchin · Jul 2, 2008

Well slap my ass and call me Judy! How long have they been selling it in powder form? This is great news for me because now I don't have to pay for shipping water thousands of miles

Murray

PVia · Jul 3, 2008

What's the formula for making the ammonium fixer?

Is this any cheaper than buying the premade TF4...or is it a TF3 recipe?

Paul Verizzo · Jul 3, 2008

Photo Engineer said:
Yes, but anyhow you can buy them at any hardware store in the US. They are fine filters that are used to remove debris from paint.

They are also used by physicians to detect kidney stones.

PE

I've never seen a paint filter that wasn't a paper cone with a cheese cloth filter near the point. They only catch chunks. Maybe there are other, better ones?

I use an old Melitta coffee by the cup filter holder and, of coure, a filter. Much, much finer. Catches real tiny stuff as any coffee drinker knows.

Paul Verizzo · Jul 3, 2008

Not the deal that you think!

MurrayMinchin said:
Well slap my ass and call me Judy! How long have they been selling it in powder form? This is great news for me because now I don't have to pay for shipping water thousands of miles

Murray

OK, this is off the top of my head from when I looked into these matters six months ago.

A gallon of 60% AT with shipping will cost you about $25. It has about 5 pounds of AT in it, voila, $5/lb of dry chemical.

The PT dry is almost $10/lb, IIRC. There are also alleged issues of "instability," whatever that might mean.

Photo Engineer · Jul 3, 2008

Paul Verizzo said:
I've never seen a paint filter that wasn't a paper cone with a cheese cloth filter near the point. They only catch chunks. Maybe there are other, better ones?

I use an old Melitta coffee by the cup filter holder and, of coure, a filter. Much, much finer. Catches real tiny stuff as any coffee drinker knows.

The paint filter is capable of catching millimeter or less sized particles and it does not use cheese cloth. It is used in different grades which is what may be confusing you. Doctors use them to catch kidney stones for analysis. They prescribe them in the right 'band pass' size for the patient.

PE

Photo Engineer · Jul 3, 2008

Paul Verizzo said:
OK, this is off the top of my head from when I looked into these matters six months ago.

A gallon of 60% AT with shipping will cost you about $25. It has about 5 pounds of AT in it, voila, $5/lb of dry chemical.

The PT dry is almost $10/lb, IIRC. There are also alleged issues of "instability," whatever that might mean.

Please give your references for instability. Thanks.

PE

srs5694 · Jul 3, 2008

PVia said:
What's the formula for making the ammonium fixer?

Is this any cheaper than buying the premade TF4...or is it a TF3 recipe?

There are many ammonium thiosulfate-based fixer formulas, TF-3 among them. The last time I checked, none was less expensive than the less expensive commercial fixers, such as TF-4 and Kodak Flexicolor fixer (the C-41 fixer; it's also usable with B&W products). My calculations at the time included shipping estimates; however, my cost data is a couple years old, so it's possible it's now less expensive to mix your own.

Paul Verizzo · Jul 3, 2008

Photo Engineer said:
The paint filter is capable of catching millimeter or less sized particles and it does not use cheese cloth. It is used in different grades which is what may be confusing you. Doctors use them to catch kidney stones for analysis. They prescribe them in the right 'band pass' size for the patient.

PE

You might well be correct, PE. I've never been offered grades of filters, even buying and use auto paints. They are the most critical and expensive, compared to home paints.

And perhaps I should have said "cheese cloth like."

Live and learn!

Paul Verizzo · Jul 3, 2008

Photo Engineer said:
Please give your references for instability. Thanks.

PE

Haven't a clue, but I saw that a number of times researching fixers which led to the paper I wrote. I came to sense it was urban legend or something, especially if you took the precaution of keeping it dry.

But here's a search to do more digging: Dead Link Removed

Photo Engineer · Jul 4, 2008

According to the MSDS, the decomposition is over 300C and it produces Hydrogen Sulfide gas. All of the data I have is that if it is poorly kept (warm and moist for example), it can decompose, but routinely stored it should be all right. Don't get me wrong, there can be problems and residual sulfur may be one manifestation but not in this case. The Formulary product appears to be OK as far as I can tell.

As for paint filters, two local hardware stores here stock them in 3 grades, fine, medium and small, and the hospital supply stocks them in at least one fine size made for them. I use them for washing and straining emulsions.

PE

Paul Verizzo · Jul 4, 2008

Photo Engineer said:
According to the MSDS, the decomposition is over 300C and it produces Hydrogen Sulfide gas. All of the data I have is that if it is poorly kept (warm and moist for example), it can decompose, but routinely stored it should be all right. Don't get me wrong, there can be problems and residual sulfur may be one manifestation but not in this case. The Formulary product appears to be OK as far as I can tell.

As for paint filters, two local hardware stores here stock them in 3 grades, fine, medium and small, and the hospital supply stocks them in at least one fine size made for them. I use them for washing and straining emulsions.

PE

As I said, I suspected that AT's instability became a fact by being repeated.

Maybe they got mixed up with ammonium thioCYANATE. Now, there's the definition of hygroscopic! Individual crystals melt into a blob of liquid in not too many minutes in air, at least here in FL.

I think I'll get some of those graded paint filters....just in case I have a stone!

Photo Engineer · Jul 4, 2008

I have a drawer full of the filters to use in emulsion making and in case I get a stone.

I have a 1 # jar of ammonium thiocyanate that seems just fine. And, due to the lake, Rochester is not noted for its dry weather.

PE

Sean McEntee · Jul 5, 2008

Most paint filters are too coarse; use a coffee filter to filter your chems.

lensmagic · Jul 5, 2008

Sean McEntee said:
Most paint filters are too coarse; use a coffee filter to filter your chems.

Would you recommend using a paper coffee filter??

Sean McEntee · Jul 7, 2008

Yes. I have a special melita coffee filter holder which is not to be confused with the one in the kitchen. Just regular cheap filters or if you are feeling flush Chemex (if they are still in business) makes a really nice coffee filter.

Somehow I missed page two of this thread where paint filters were discussed in detail. I have only seen the rather coarse ones, definitely 1mm or larger mesh...

lensmagic · Jul 7, 2008

Formulary/Bud Wilson said:
The powdered Ammonium Thiosulfate requires +-120degrees F to disolve. Also this product may have a reaction with iron compounds within your water supply, if on a well or Chlorine if on a city water system. Your filter system should have the ability to deal with either of those.
The product also has only come from one lot # so it is the same material that you have gotten from us before.
If you want to use your filtered tap water and dissolve at room temp, just simply filter, as mentioned before thru a coffee filter or paint filter and use normally.
Thanks for bringing this to our attention and we will run a test of this today.
If we find a problem we will post on this thread.
Thanxs
Bud

Darkroom day arrived and I processed some roll film and sheet film. I used a ten per cent solution of the ammonium thiosulfate I described above. The ammonium thiosulfate dissolves just fine at room temperature, but I dissolved the ammonium thiosulfate in distilled water heated to 125 degrees Fahrenheit. The resulting solution appeared as below left. I noticed no difference in the appearance from the tap water sollution I originally used. The second photo shows material I trapped in a metal coffee filter which was too coarse. Quite a bit of undissolved material passed through the filter. The last photo shows the material adhering to a mixing vessel after the solution was poured out. As before, the fixer seems to work fine. But it leaves a fine crystaline coating on reels, drums and tanks, as well as all mixing paraphernalia.

Photo Engineer · Jul 8, 2008

Alert Bud and arrange to send him a sample.

PE

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