Hardener questions and a hardener bath

[avatar]

Does whether a hardener was used during processing have and effect

on how vulnerable film or paper is to scratches once it is dry?

This first question please don't answer based on what you have heard

or read or been told. I'm looking for an answer from a chem expert

who can actually give a detailed explanation... plus I've asked this

question so many times and gotten 3 different answers (it only

protects while wet, only while dry, and it protects while wet and

dry) I do know they severely harden X-ray film b/c they expect

doctors and medical personal to brutalize the x-ray negs

 

I'm using D-76, Indicator stop, F-24 (non-rapid fixer, sodium

thiosulfate), then hypoclear. There is no hardener. Can I add

another bath of some sort of hardener between the fix and the

hypoclear? Or before the Fix? Or after the hypoclear? I know the

hardener needs an acid buffer to work... what should I use? Acetic

acid? I need a seperate bath b/c I can't mix stuff into the stop fix

or hypoclear b/c they are school chems. Can I reuse the hardener

bath? What chemicals would I need? I'd like to mix it up myself.

They only seem to sell seperate hardeners for mixing into the fix

and then only in large quantities (smaller quanities when you buy

fixer+hardner). I can proll swipe the chemicals from the chemistry

dept.

 

Does hardener affect how long I must rinse?

[ryuji_suzuki]

> Does whether a hardener was used during processing have and effect

on how vulnerable film or paper is to scratches once it is dry?

 

For practical purposes, no.

 

> please don't answer based on what you have heard or read or been told.

 

What's Internet?

 

> I'm looking for an answer from a chem expert

who can actually give a detailed explanation... plus I've asked this

question so many times

 

If you go to a decent library and do a bit of search, you'll find detailed explanation in a few hours.

 

> it only protects while wet, only while dry, and it protects while wet and dry

 

If you know that the mechanical strength of wet emulsion is limited by that of gelatin, and hardners increase the strength by increasing the cross linking, you'll almost immediately know that all the practical benefit comes when the film is wet (or relative humidity of the air is very high).

 

Dry abrasion, wet abrasion, dimensional stability, etc. are different things and they are also measured differently. Emulsion hardeners are concerned about wet abrasion and swelling but not dry abrasion, which is usually dealt with different means if necessary.

 

Some commonly used hardners are not as stable as metallic silver and may limit the longevity. I don't know how likely it is, however.

 

> Can I add

another bath of some sort of hardener between the fix and the

hypoclear?

 

For what purpose? It is somewhat likely that you don't need it or that such a process is inadequate.

 

> I know the hardener needs an acid buffer to work...

 

Not necessarily. That applies only to hardening bath containing chrome alum, potassium alum or alminum alum. For these, pH should be maintained around 4.6 and therefore acetate buffer is often used. Further addition of boric acid is usually preferred as a further resistance to pH rise and minimize insoluble reaction products when pH actually rises. There are dozen other hardening agents known and probably used today.

 

> What chemicals would I need?

 

It all depends on what effect you want and which kind of hardening bath you use.

 

> Does hardener affect how long I must rinse?

 

If used with or as an adjacent process of fixing, washing out fixer and its harmful reaction products requires longer washing time.

[art_haykin]

From the net: >> A hardener is usually only used in film development to protect the emulsion from softening and scratches. Hardener used in print development makes spotting, toning and other manipulations difficult and is not advised. Potassium alum is a common hardening agent. A buffer, usually boric acid is used to maintain the acidity of the fixer when a hardener is used.

[ryuji_suzuki]

> Potassium alum is a common hardening agent. A buffer, usually boric acid is used to maintain the acidity of the fixer when a hardener is used.

 

Boric acid alone is by no means enough to maintain pH necessary for potassium alum to work as it is supposed to.

[robert_marvin]

I've had very good results on film with this hardening stop bath

from the 1951 "Leica Manual":

 

Water, 500 ml

Chrome Alum , 10 grams

Sodium Bisulfate, 10 grams

 

Dissolve theChrome Alum comletely before adding the Sodium

Bisulfate. Mix imediately before use at the same temp as the

developer and fixer. (note--not in the book--use good

ventilation-the smell is rather pungent!).

 

Leave film in the stop bath for 5 minutes. Disgard the solution

after use.

 

This stop bath makes the emulsion surface almost as glossy as

the film base. I don't always bother to use the stuff (and, frankly,

I'm not sure its necessary) but it gives at least the illusion of

scratch-proofing your negatives

[ed b.]

For the most part, hardeners are unnecessary with contemporary emulsions. I believe they do increase wash times considerably, so I would advise washing thoroughly before hardening. I have a page on my web site that gives Kodak's standard <a href=http://unblinkingeye.com/Articles/Developers/Hardeners/hardeners.html>hardening formulas</a>.

[richard_trochlil]

"....Hardener used in print development makes spotting, toning and other manipulations difficult and is not advised..."

 

I assume this means during the print development PROCESS, rather than in the print developer.