Hypercat / Obsidian Aqua Question

I've developed an itch to try either or both Hypercat and Obsidian Aqua developers. Both list Sodium Carbonate as an ingredient. However, I can find no reference as to the form, anhydrous or monohydrate. I'm not a chemist, but would think that it would make a difference. Can anyone shed some light on this please?

Thanks

Born2Late said:

I've developed an itch to try either or both Hypercat and Obsidian Aqua developers. Both list Sodium Carbonate as an ingredient. However, I can find no reference as to the form, anhydrous or monohydrate. I'm not a chemist, but would think that it would make a difference. Can anyone shed some light on this please?

Thanks

Click to expand...

You can use either one. I believe, the mass stated by the formula is for the anhydrous form. Have a look at (there was a url link here which no longer exists) for the conversion factor.

While the blog post for obsidian aqua doesn't mention hydration of Sodium Carbonate directly, we can infer it from the text:

• The text mentions "in a 0.666% solution of potassium carbonate (6.66g/ liter), or a 0.5% solution of sodium carbonate (5g/liter)"
• 6.66 g Potassium Carbonate equals 0.048 mols, and there is no ambiguity regarding hydration for this compound, it exists only in anhydrous form
• 5.00 g Sodium Carbonate are 0.047 mol of anhydrous form, or 0.040 mol of monohydrate, or 0.017 mol of decahydrate

We can therefore assume, that the anhydrous form of Sodium Carbonate is meant in this blog post and recipes derived from that post.

Thanks for the help. As I said, I'm not a chemist.

Thread on LFPF from Jay DeFehr, who "developed" them.
http://www.largeformatphotography.i...atechol-staining-developer&highlight=hypercat

When a particular hydrate is not specified it usually means to use the one that is stable under usual storage conditions. In this case that would be the monohydrate.

Born2Late -- I hope you'll keep us apprised of your experiences with Obsidian Aqua. I bought some OA from Jay DeFehr when he was listing it and 510-Pyro on eBay. While I've had some success using 510-Pyro, I was never able to get anything approaching box speed from OA. I'd like to think others have had better luck than I have!

Well folks, I have mixed my OA and tested the first roll (HP5+). I wouldn't call it a complete failure, but certainly a big disappointment. The contrast is very high and shadow detail is all but completely missing. I would concur with Trask's comment about box speed. I'll probably try again at an IE of 100 and reduce the development time. Alternatively I may shoot a roll with a repeating series of exposures at box +1, +2 and +3 exposures of the same subject, then develop clips with various times.

I had almost nothing but disappointment with hypercat. On the odd occasion it was very very good, but when it was bad it was horrid.

Because so few people use oa/hypercat, there's no large established base of times and dilutions and films to work from, so you have to be prepared to test a lot,and expect some failures. Plus of course they are developers created at home rather than commercially.

In the end I gave up and decided that if I ever wanted to try a staining developer again I'd give pyrocat-hd a go, simply because of the larger user base.

I've tried a couple of Jay DeFehr's developers - Hypercat and 510Pyro. Let me say that I'm one person who always seemed to get along with him - it's too bad he doesn't seem to post on any forums or his sites anymore. Jay always said he shot pictures of his family - not landscapes, still life, etc. As a result, I think he was most interested in skin tones and other rather high values. I never got much shadow detail out of either developer, and if you look at the photos Jay posted online, I don't see much shadow detail in them, either. As pdeeh said, there is not much of a user base, and I didn't do a lot of experimenting. I had already worked out times for Pyrocat HD, so I just wasn't so interested in working out times for other developers.

I'm pretty sure Jay was using ordinary sodium carbonate - maybe even Arm and Hammer washing soda.

You might want to try increasing exposure and reducing agitation rather than development time. It's time in the developer that produces the shadow values - high values can be controlled by reducing agitation.
juan