[pure-silver] Re: Formula #87 in Anchell
- From: Robert Hall <robert.g.hall@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Tue, 17 Jan 2012 13:38:50 -0700
Richard,
I would pay hard money to have all you have written on fixers in a book.
Thank you,
Robert Hall
www.RobertHall.com
www.RobertHall.com/workshops
www.facebook.com/robert.g.hall
On Mon, Jan 16, 2012 at 9:29 PM, Richard Knoppow <dickburk@xxxxxxxxxxxxx>wrote:
>
> ----- Original Message ----- From: "Bogdan Karasek" <BKarasek@xxxxxxxxxxxx
> >
> To: <pure-silver@xxxxxxxxxxxxx>
> Sent: Monday, January 16, 2012 5:34 PM
> Subject: [pure-silver] Formula #87 in Anchell
>
>
>
> Hello all,
>>
>> Just needed some advice from those who know about such things....
>>
>> More and more, I find myself mixing my own chemicals. For paper, I can
>> now get Hypo (Sodium Thiosulfate) in 25kg bags from a chemical firm. I
>> use the 2 tray method of fixing. But what about film? I checked Anchell
>> and found this interesting formula (#87 Odourless Acid Hardening Finishing
>> Bath for film or paper)
>>
>> I have all the ingredients:
>>
>> Sodium Thiosulfate, 240gr
>> Sodium sulfite (anhydrous), 15.0gr
>> Acetic Acid 28%, 48.0ml
>> Balanced Alkali, 15gr
>> Potassium Alum, 15gr
>> Water to make make one Litre.
>>
>> I don`t have any Potassium Alum , but Anchell tells me that the Potassium
>> Alum is the hardening agent in the solution, so if I leave it out, do I
>> have a fixer that is non-hardening?
>> Am I correct in this assumption and can I proceed without the Potassium
>> Alum. I will be mixing 17 Litres in tanks for 8x10 Tri-X.
>>
>> Later, I want to develop some 4x5 Efke PL 25 Otho. The Efke emulsions
>> tend to be soft and a hardening fixer is recommended.
>>
>> Is there a commercial name for Potassium Alum, something I could get at
>> the pharmacy or supermarket, so I could use it with the Efke fixer, or am I
>> still good without the Alum?
>>
>> Can I substitute Baking Soda for the Balanced Alkali, and if so, in what
>> proportion, or are they interchangeable in terms of quantity?
>>
>> Cheers,
>> Bogdan
>>
>>
>> Jean David has already pointed out that this is Kodak F-6. The main
> difference between this and Kodak F-5, which is the standard formula is the
> use of Kodalk Balanced Alkali AKA sodium metaborate in place of borax.
> A couple of notes: Sodium thiosulfate will fix all by itself but will
> oxidize rapidly without the addition of some sodium sulfite to protect it.
> The sulfite has the further effect of preventing staining from developer
> reaction products since the developer will continue to be active until the
> hypo dissolves enough halide. If a plain, non-acid bath is desired about 5
> grams per liter of sulfite is sufficient. In hardening baths enough
> additional sulfite is added to prevent the thiosulfate from being
> decomposed by the necessary acid typically about 15 grams per liter.
> Thiosulfate will fix regardless of the pH of the bath its in but the
> inorganic hardeners often used require the bath to be acid to work. The
> most common hardener is potassium aluminum sulfate more commonly known as
> alum or white alum. A few fixing bath formulas call for chrome-alum which
> is potassium chromium sulfate. Chrome alum results in more complete
> hardening of the emulsion but can produce staining so it was never used for
> printing paper. It was most often used for high-temperature processing.
> The use of acid in a fixing bath even without the hardener has some
> advantage, mostly that is stops the developer immediately, allowing more
> controllable development, and also prevents the generation of reaction
> products by the residual developer. The disadvantage of acid is that it
> tends to prolong washing. The rate at which thiosulfate diffuses out of the
> emulsion depends partly on the relative electrical charge of the molecules
> of the emulsion, when acid the charge tends to attract, thus bind, the
> thiosulfate ions; when neutral or alkaline, the charge tends to repel the
> thiosulfate ions. In addition white alum hardener has a specific mordanting
> property for both thiosulfate and its reaction products. The effect takes
> place only when the emulsion is acid. However, the hardening also is
> effective only as long as the emulsion is acid. While both the mordanting
> and electrical binding can be eliminated by treating the emulsion in an
> alkaline bath such a bath will also destroy the hardening. However, both
> mordanting and charge binding are eliminated at neutral pH (for typical
> photographic gelatin) while the hardening is preserved. So, treating in a
> wash aid which produces a neutral condition will accelerate washing without
> destroying the hardening. The use of sulfite as a wash aid has the
> advantage over other alkalis that it has an ion exchange effect on the
> thiosulfate so accelerates washing even when the emulsion has been fixed in
> a neutral or alkaline fixing bath.
> Almost all standard fixing baths have about 240 grams per liter of
> crystalline sodium thiosulfate in them. Anhydrous thiosulfate works as well
> and less is necessary. However, most fixer formulas were written at a time
> when the crystalline form was the most available. The reason for this
> quantity traces to research done at Kodak a very long time ago. The first
> research into the optimum amount of thiosulfate was done with dry film. It
> turned out that the condition of the emulsion is important: when the
> experiments were repeated some years later with wetted film it was found
> that the rate of fixing Vs: hypo concentration did not reach a peak at 240
> grams, as shown in the first experiments, but continued to become shorter
> as the concentration was increased. Nonetheless, the amount became a
> standard and continues to the present.
> The use of ammonium thiosulfate in place of sodium thiosulfate results
> in a fixing bath that is faster and less sensitive to the accumulation of
> reaction products. This was known for decades but "rapid" fixer was not
> popular because ammonium thiosulfate in dry form is not stable and liquid
> concentrate is expensive. Also, when made acid, as in a standard fixer
> formula, ammonium thiosulfate tends to dissolve fine metallic silver
> particles resulting in bleaching unless fixing time is carefully regulated.
> This also made it difficult to use in a hardening bath since the hardener
> might take considerably longer to work than the fixer. BTW, the slowness of
> the hardener is one reason that older instructions often specify extremely
> long fixing times. Fresh sodium thiosulfate fixer will fix out most
> emulsions in a couple of minutes but the hardener may need ten or more
> minutes to work. Even tabular grain film emulsions may fix out faster than
> is necessary for hardening and certainly film-strength rapid fixer will.
> Note also that all acid fixing baths contain an acid buffer
> combination. This is to maintain the pH in a range where the hardener will
> work. It is to compensate for carried over developer and also carried over
> stop bath. If its desired to keep the development stopping property even in
> a non-hardening bath a buffer is still necessary to prevent the fixer from
> becoming alkaline from carried over developer or too acid from carried over
> stop bath, which could cause decomposition. Where an ammonium
> thiosulfate bath is used without acid, or with reduced acid in a
> non-hardening bath the bleaching effect does not take place so it can be
> used full strength for even warm tone papers without affecting either
> density or image color.
> A rapid fixer can be made by the addition of ammonium chloride to a
> conventional fixing bath, as in Kodak F-7, but is not as satisfactory as a
> bath made with ammonium thiosulfate.
> A good non-hardening fixing bath with reduced acidity is Kodak F-24
> given below. Because of the fairly high pH there is less tendency for this
> bath to produce sulfur dioxide gas, the familiar hypo odor, which many find
> particularly irritating.
>
> Kodak F-24
>
> Water (at about 125F).............500.0 ml
> Sodium thiosulfate, crystalline...240.0 grams
> Sodium sulfite, desiccated.........10.0 grams
> Sodium bisulfite...................**25.0 grams
> Water to make.......................1.0 liter
>
> Note: if anhydrous thiosulfate is used the water temperature should not be
> over about 90F to prevent decomposition. Crystalline hypo is extremely
> endothermic and will rapidly cool the water its mixed in.
>
> Sodium thiosulfate, crystalline had an approximate formula weight of
> 248 and anhydrous of 158 so that if you want to use anhydrous in place of
> crystalline the ratio is: 64%
> I don't have formula for rapid fixers at hand but ammonium thiosufate
> can be substituted for sodium thiosulfate in standard formulas by
> conversion of amounts using the formula weights. Formula weight for
> ammonium thiosulfate anhydrous is 148.2. Typical liquid concentrates are
> about 58%. My memory is that rapid fixers have rather more thiosulfate in
> them than standard fixers.
> Another note: sodium metaborate can be made by combining borax and
> sodium hydroxide in solution. The amounts are: Sodium hydroxide....14.5
> grams, borax, 69 grams, equals 100 grams of sodium metaborate. Adjust these
> amounts according to the amount of metaborate you need in the formula.
>
> I didn't really mean to write a treatise when I started out but the fit
> was upon me.
>
> --
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
>
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