When to use hypoclear?

[cyrus]

In washing some film yesterday it occurred to me that dunking the film in hypoclear right after fixing is probably not the most efficient thing to do -- after all, at that stage the hypoclear is merely "neutralizing" the fixer that that can be easily removed with a short rinse, and so most of the hypoclear is simply being wasted & is expended on large amounts of fixer that can be more easily rinsed off.

So shouldn't the hypoclear step be saved until after the wash has had a chance to get rid of the bulk of fixer, leaving the small amount that can then be removed chemically with hypoclear?

(Of course you still need to wash the hypoclear out too.)

[Erik Larsen]

Wash for a couple minutes before you use hypo clear and you'll be good to go.
Regards
Erik

[Sevo]

So shouldn't the hypoclear step be saved until after the wash has had a chance to get rid of the bulk of fixer, leaving the small amount that can then be removed chemically with hypoclear?

IIRC at least one of the hypo clearers I've used had a fairly similar recommended procedure on the info sheet.

There is no real point using hypo clear on film or PE paper, by the way - it is a added risk as it will soften the emulsion, and on materials where the fixer cannot soak into the base complete hypo removal can be achieved using only water for the wash, without needing excessive time or amounts of water. It may be needed if you are forced to wash at very low temperatures or with a very limited amount of water - but these are conditions you'll hardly ever have except on location in a expedition tent.

[Heroique]

There is no real point using hypo clear on film or PE paper, by the way – it is an added risk...

I prefer the risks of hypoclear over the risks of no hypoclear – film & paper.

[Ken Lee]

There are fixers which use no Hypo, IE no Sodium Thiosulfate. There are also alkaline fixers, which require no washing aid at all.

We only need to remove Hypo when Hypo is used.

The classic TF-3 formula is an alkaline fixer that does not use Hypo.

According to Anchell and Troop, in The Film Developing Cookbook, Alkaline Fixers have the following advantages over more traditional Acidic formulas:

• Less danger of over-fixing
• Shorter washing times
• More archival
• Greater capacity
• More stable
• Can be formulated to have low odor

[ic-racer]

Wash for a couple minutes before you use hypo clear and you'll be good to go.
Regards
Erik

Yes. For example in adapting the six-bottle Jobo system to B&W, I use bottle #3 for Fixer, #4 for a water rinse and #5 for the hypoclear (Permawash in my case.)

[photobymike]

I use Orbit because it saves water and it turns my purple negatives clear... makes scanning a little easier

[Doremus Scudder]

Hypo-clearing agents (Kodak HCA for example) work for fixers based on sodium or ammonium thiosulfate equally well. Rapid fixers (those with ammonium thiosulfate and not "hypo," which is another name for sodium thiosulfate) benefit from a hypo-clearing agent as well.

The hypo-clear can be used without an intermediate rinse, but the capacity is reduced. Kodak gives capacity numbers for both methods. Rinsing is recommended for maximum capacity of the hypo-clear. Since hypo-clearing agents are usually sodium sulfite solutions, they do not last that long after being mixed. If, like me, you use hypo clear one-shot, maximizing capacity may not be a factor. Do the numbers and decide for yourself.

As mentioned, the use of a hypo-clearing agent is of primary importance with fiber-base papers, but it does speed up washing with film and RC papers as well. The risks from softened emulsions are not usually a factor. The emulsion is not softened that much and normal care in handling of the film usually prevents any problems.

Alkaline fixers wash out more easily, but the use of a hypo-clearing agent, especially when using fiber-base papers, is still recommended for shortening wash times.

Do not use hypo-clearing agents if you use a staining developer like PMK or Pyrocat, since the hypo-clear will remove the stain. If you do not use a hypo-clearing agent, make sure you wash adequately.

There are different wash times with and without the use of a hypo-clearing agent for films and papers. Without hypo-clear, I wash my films for 30 minutes. Since most of my negatives are developed in staining developers, I mainly use hypo clear only when printing.

Check out the sticky thread at APUG about film washing http://www.apug.org/forums/forum37/8...hing-test.html for a detailed examination of the subject regarding film washing times and hypo-clear.

Bottom line, use a hypo-clearing agent and wash well unless there is a good reason not to use the hypo-clear. If you don't use a hypo-clear for film and RC paper (staining developers/alkaline fixer), then make sure you wash adequately. The times are generally three or four times longer. Films and RC papers can be over-washed a bit with no ill effects. Better to err on the side of safety.

It is easy to mix your own hypo-clear: 1 Tablespoon of sodium sulfite and a pinch of sodium metabisulfite per liter makes a nice hypo-clearing bath.


Best,

Doremus

[nolindan]

Before it's true composition was known S. Thiosulfate was thought to be S. Hyposulfate - hence the 'hypo' nickname.

"Hypo", then, refers to both S. Thiosulfate of traditional acid fixers and the A. Thiosulfate of rapid and alkaline fixers.

The only common fixer that doesn't use Thiosulfate uses Potasium Cyanide instead. If you use Cyanide for your fixer you don't need HCA, it is true.

"Hypo Clearing Agent" should better be called "Thiosulfate Clearing Agent", but I guess it doesn't have the same marketing 'ring' to it.

I use HCA on film not because it gets the fixer out faster than water but because it gets the purple anti-halation dye out faster than water alone.

HCA doesn't destroy Thiosulfate, it just makes it easier for the Thiosulfate and it's products to leave the emulsion. And it's not really the Thiosulfate itself that's the problem but the Thiosulfate products that are left over from the fixing process and have a real affinity for gelatine. HCA does have a softening effect of gelatin as it modifies the pH to the 'isoelectric point' so that gelatin has less chemical binding strength. Soft is good - hard is bad - when it comes to washing film and paper; soft gelatine has water diffusing through it, carrying away the fixer products. The gelatin hardens up again when the HCA is washed out.

[swmcl]

I am thankful to the last two posters in this thread. Both have explained themselves brilliantly. I am in the process of finding out what I need to do contact printing and these responses are most welcomed. It is a joy to find concise information.