Blix clear part going bad

[darkroom_rookie]

Part B of a two-part Tetenal blix started going bad this week, at about 1/4 left in the bottle. Yellow-greenish precipitate started forming at the bottom and what looks like flecks of dust can be seen on the surface of the liquid. How to filter it before mixing? Should the paper be blixed longer?

 

[Mike Wilde]

That is likely mostly the ammonium thiosulfate aqueous solution. It is usually sold as a 60% solution on its own. There may be other things likel sodium silfite mixed into your concentrate.

Don't use it. The flakes you see are clumps of tiny sulphur coming out of the solution. This is not uncommon with old amm thio. The tiny flakes will cause all sorts of white spots on your processed film/print.

I am not sure how comfortable you are mixing from scratch; there are work arounds, since the iron containing part A is the more expensive part. If it is for use on film, I would suggest getting another kit, or get used to bleaching and fixing as separate steps.

 

[stefan4u]

Just like Mike said, don’t use this rotten fix-part, or trouble will guaranteed.

By the way, are you talking about RA-4 chemicals?

If so, you could take some Tetenal Superfix (probably every other acidic BW film fixer will work too) in the same amount (about 200 ml/L) to substitute the original fix part. This is NOT state of the art; the resulting Blix will be off concerning pH and does not have a long shelf life, likely a result of wrong concenrtation of antioxidants and sequestering agents...
But the one time I did this, in order to replace oxidized fix of my Ektaprint RT Blix, it worked pretty well with increased replenishing rate.
Could not remark different print results and the pictures are keeping well.

I would recommend to try this, if you have a larger amount of the bleaching part left…

Regards, Stefan

 

[Photo Engineer]

TF-5 will probably work as well. It has the right pH for RA fix concentrate so used at the same volume level as the bad fix it should give very good results.

PE

 

[darkroom_rookie]

Gentlemen, thank you for your answers. Yes, it's Tetenal paper blix BX, designed for 30-36 degrees C. I'll look for Superfix from the local supplier.

 

[darkroom_rookie]

...which proved fruitless. All the ingredients for mixing my own fixer are available locally, so why not mix my own? Presumably I need a non-hardening fixer, correct? Also, looking at the Tetenal BX MSDS, I noticed it contains ammonium hydrogen sulfite. How important is that ingredient in a paper blix?

 

[Photo Engineer]

It prevents stains.

PE