Precipitate in tetenal ra4 blix

Domin · Jul 17, 2008

Right now I'm making color prints using tetenal ra4 kit in trays. There is quite a lot of pinkish (its hard to tell its color, as the blix is deep red-brown) precipitate in the blix. The blix seems to work fine but the precipitate was there when I made fresh solution. Its smaller particles stick to paper and needs to be wiped off as it won't come with just a wash.

I have some prints made over a year ago, when I had just the same issue, and they are fine.

I just filtered blix through a coffee filter. Still seems to work fine.

What's that? Should I worry?

srs5694 · Jul 17, 2008

I don't recall the brand, but one brand of RA-4 blix I tried (part of a kit) produced the sort of precipitate/grit you mention when first mixed. After sitting in my tray for an hour or so, it mostly dissolved, although I could still feel it when I pulled prints from the tray. So far I've noticed no problems with prints made with this kit (it's been at least a year since I used it).

Overall, I'd recommend you mix your blix an hour or so before you need to use it, then wipe the prints with your hand or a squeegee when you pull them from the blix. That should at least minimize the issue.

Photo Engineer · Jul 17, 2008

You have either exceeded the hard water limit and have formed some metal salts or the hypo in the blix is going bad. Either way, this is not good! Some blix formulations skimp on EDTA or stabilzer, or have the wrong pH.

PE

Domin · Jul 17, 2008

The pecipitate was actually present in blix concentrate. I filtered it and washed the precipitate. Seems to be insoluble in water. Its light brown much like cappuccino. Overall it looks and feels a bit like clay, no smell.

Photo Engineer · Jul 17, 2008

Which part of the concentrate was it in, the red part of the clear part?

If in the red part, it is ferric and ferrous hydroxide and the blix is either going bad or was prepared improperly from impure materials or water.

PE

Domin · Jul 17, 2008

There's just one part - concentrate dissolved 1+4.

Tomorrow I'm going to buy next one. I'll carefully look at the bottle before buying.

Photo Engineer · Jul 17, 2008

A one part blix is nearly impossible to keep for any length of time. The precipitate can be just about anything because you have basically a mixture of an oxidant with several reductants.

The Kodak and Fuji kits come in 2 parts with the oxidant in one container and the reductants in another container to give maximum lifetime and prevent the problem you are seeing. It may blix, but it sure is near the end of its useful lifetime.

PE

srs5694 · Jul 17, 2008

I believe I've used the same product Domin used. I don't recall the brand, but it could well have been Tetenal, as he's using. The blix shipped in one bottle, but the two components didn't mix well and separated naturally (like oil on top of natural peanut butter, or oil and water). The instructions said to shake the bottle vigorously to mix the two parts, then measure out the desired quantity and dilute it. The remaining concentrate, if less than the full bottle was used, would separate out, but the mixed and diluted working solution wouldn't; it would stay mixed. As I noted in my earlier post, the gritty stuff would slowly dissolve over an hour or so, although there were hints of it even then, at least up to three or four hours after mixing.

I can't rule out the possibility that this grit is evidence of a problem, as PE suggests. At the time I assumed it was normal for this particular product.

Photo Engineer · Jul 17, 2008

The mixture should not form 2 phases. Both are water soluable, so having 2 phases is quite unusual. There should be no sediment or grit.

PE

srs5694 · Jul 17, 2008

The blix is designed to separate out like that, PE. My recollection is that the box or documentation specifically describes this. Obviously Kodak doesn't do it that way, but Tetenal (if that's who made the product I'm remembering) does. I didn't design the product and I don't have any more of it, so I can't provide much more in the way of specifics, but the separation aspect is not a defect; it should separate, based on its design.

Whether the grit/sediment/whatever is a side-effect of this design or reflects the product going bad is another matter. I don't recall the documentation mentioning this detail.

Actually, I just checked, and B&H sells Fotospeed Mono RA-4, which may be what I used. (I don't know if this is the same as the Tetenal that Domin has used, but under a different name.) The B&H Web site mentions that "the active ingredients are in powder form in the concentrate which extends the keeping properties of the concentrate and the active life of the working solution" and "shaking the bottle before mixing puts the ingredients into suspension to enable partial mixing of the concentrate." Make of that what you will.

Photo Engineer · Jul 18, 2008

It may be "designed" to be that way, but remember that one part is oxidant and one part is reductant and they have an interface where things can happen. Bad things. The Ammonium Ferric EDTA (or other complex) becomes a mixture of Ferrous Hydroxide and Ammonium Ferrous EDTA and the Hydroxide precipitates. This reaction causes hypo to become Sulfur (a precipitate) and Hydrogen Sulfide gas which dissolves in the near neutral blix components while Sulfite becomes Sulfate. The activity goes down and more and more precipitate forms.

If the blix is old enough, silver and silver halide remain in the film or paper (well, film blixes usually leave some anyhow) and if there is any precipitate present, it can become trapped in the swollen gelatin. Even 1 mg / dm sq will give you considerable stain. I have run analyses on blixes that precipitate and papers and films processed with them.

Another fault can be too much alkali, or not enough EDTA which also leads to Ferric and Ferrous Hydroxides. This is also a bad situation.

In film, you can even see the trapped precipitate as a type of reddish grain.

PE

Richard Harris · Jul 19, 2008

I had a similar problem with Kodak 2 part blix with the hypo clear part precipitating. I tried to heat it, stir it, and generally mess with it; all to no avail.
I ended up taking PE's advice and dumping it. Now I keep my blix components as cool as possible to slow chemical changes. I suggest you do the same. Blix is an important component in development. The results of poor bleching and fixing may not be apparent immediately. You may pay later for using exhausted components.

Photo Engineer · Jul 19, 2008

If part 2 becomes cloudy or forms a yellowish precipitate it is old and has spoiled. It is hypo + sulfite and it has oxidized just as a normal fix can oxidize. Even Kodak fixers and blixes in 2 parts can go bad if kept poorly or left too long. As stock moves more slowly, I suspect we will see more of this.

PE

Precipitate in tetenal ra4 blix

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