Capacity/Exhaustion of HCA

[jstraw]

What's the capacity of HCA for fibre prints? Or perhaps, how does one determine when it's exhausted? That might be a better question.

 

[dancqu]

What's the capacity of HCA for fibre prints?
Or perhaps, how does one determine when it's exhausted?
That might be a better question.

The instructions on my box of Kodak HCA indicate with
no rinse 80 8x10s per gallon, 1 minute rinse prior, 200 8x10s.

I believe all off-the-shelf HCAs are dependent upon a sulfite
or sulfites as the active ingredient. The sulfites oxidize to sulfate.
I've not heard or read of any off-the-shelf indicators of it's exhaustion.
I think potassium permanganate would do well. I had in mind testing
with permanganate but have little incentive. The usual stuff does
go bad so I've switched to bicarbonate of soda for which there
are no published guidelines. I do end product testing so can
use it at my own imperil. Dan

 

[jstraw]

Thanks, the one gallon pouches I bought didn't have that information listed.

 

[jeroldharter]

I use Heico PermaWash because it is cheap and very easy to mix (3 oz in 64 oz of water or something like that). Very easy to mix on the fly. I would have a hard time generating enough FB prints in one day to exhaust a gallon of it. I change it every day when I am active in the darkroom.

 

[Konical]

Good Evening,

Ditto on the PermaWash. One additional thing to keep in mind with hypo clear is that a working solution has a relatively short life in an open tray, 4 to 6 hours, if I recall correctly. When I expect a long darkroom session, I keep a sheet of thin plastic (the dry-cleaner stuff) floating on the hypo clear between prints.

Konical

 

[jstraw]

Mine is in the tray for about 5 minutes per session.

 

[Ryuji]

The processing capacity of hypo clear agent is dependent on how you use. If you give good 3-5 minutes rinse of print after fix or toning, drain prints thoroughly, and use up the working solution in a single session's time, you can go through more than that. The number is set rather conservatively, as a safety factor for people who do any of the above rather sloppily. Usually capacity of hypo clear is a non-issue as long as the user knows it is killed by aerial oxidation like developers.

There is no fast and cheap and simple way to tell if hypo clear is still good. But hypo clear is cheap to replace.

 

[jstraw]

My prints go from the second fixing bath to a circulating holding tank till I'm done printing. Then I drain the prints and they go into the HCA for three minutes where the prints are constantly rotated. Then they are drained and put back into a holding tank for additional rinsing. Then they're drained and get six minutes of constant rotation in Selenium and are again drained and put back in the holding tank while I fill the washer. They then get 60 minutes at one gallon per minute, are squeegee'd and put on drying racks overnight.

This morning I used a residual hypo test on one of yesterday's prints and there was no visible staining at all.

 

[Ryuji]

No stain with HT-2 is very good. A very light yellow is already archival and you can safely stop washing there.

Since I noted one thing. HCA is best used after selenium toning, since residual selenium toner is just as bad as residual fixer, and HCA works on both.

Some people and darkroom manuals suggest HCA before toning to "prevent staining" but with most papers this is not an issue. If preferred HCA can be used before and after toning.

The flow rate of washing tank varies, but generally, the tank capacity divided by 5 is a good number to use. If your washing tank is 5 gallon, 1 gpm is good. If selenium is followed by HCA, I think 20 min final wash is more than enough. (and of course you can test it if you worry)

 

[jstraw]

I will probably try HCA after toning and see if I get staining. If I do, I may try both before and after.

Next session, I'll mark a series of prints and take them out for testing at 20, 30, 40, 50 and 60 minutes.

I'm not a maniac for testing. I like making pictures. I'm going to nail down solid procedures and probably check them every six or 12 months.

I'm going to be testing for retained silver and fixer exhaustion too. I'm glad I bought that Darkroom Data Guide!

 

[Ryuji]

I'm not a test maniac either, but I would rather go home early than waiting for 40 extra minutes. (I rent a separate space for darkroom/studio than my residence and I usually work in darkroom til late hours.)

If you tone all your important prints, there is no need for retained silver test (sodium sulfide solution). If there's any significant amount of unfixed silver halide in the emulsion, that will show up as stain in your selenium toner bath. If only small amount of residue is in the print, it gets converted to permanent form that you won't have to worry about (as long as you see absolutely no staining on the print).

I always recommend polysulfide or selenium toning as it increases permanence and serves as an instant test simultaneously.

 

[jstraw]

Thanks Ryugi. That's helpful information.

 

[dancqu]

"A very light yellow is already archival and
you can safely stop washing there."

The HT-2 test will not indicate at archival levels. That test
will show No stain some little short of archival levels.

"Some people and darkroom manuals suggest HCA before toning..."

Including Kodak. Once again from my box of Kodak HCA:
Prior to Kodak Rapid Selenium Toning "add 71 grams Kodalk..."
per gallon then wash at 65-70 F; 20 minutes DW, 10 minutes SW.
Likely that HCA plus Kodalk was to follow an acid fixer.

A. Adams followed his second alkaline fix with a HCA plus
selenium toner. Short lived that way as the sulfite based
HCA is good for about one session.

BTW, Adams held between first and second fix. IIRC,
Mr. Rudman suggests the HCA follow the fix. Perhaps
he will chime in. I think when to hold is more important
than just something to do just any time. Dan