[pure-silver] Re: Formula #87 in Anchell
- From: harry kalish <hksvk@xxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Wed, 18 Jan 2012 11:14:59 -0500
Ditto, Richard. Thank you. ---Harry.
On 1/17/12 3:38 PM, "Robert Hall" <robert.g.hall@xxxxxxxxx> wrote:
> Richard,
>
> I would pay hard money to have all you have written on fixers in a book.
>
> Thank you,
>
> Robert Hall
> www.RobertHall.com <http://www.RobertHall.com>
> www.RobertHall.com/workshops <http://www.RobertHall.com/workshops>
> www.facebook.com/robert.g.hall <http://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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