Kodak Tri-x 7278 vs 7266

[Christian Flemm]

Dear Forum,

I'm wondering whether someone might be able to explain why Kodak retired the 7278 emulsion and replaced it with 7266 in 2003. Are there key differences in the formulation of these two emulsions that lead to, for example, a different grain structure or stronger dynamic range?

I started shooting 16mm in 2010, so have only known the '66 emulsion. I did however have the pleasure of shooting on Plus-X reversal, which I miss quite a bit.

As ever,

Christian

[Charles MacDonald]

I belive that the recommended  process was changed to avoid a chemical that the EPA had some concerns about.  Both Plus-X and Tri-X reversal got new versions, although the old versions, would work in the new process with some exposure adjustments.

Edited January 15 by Charles MacDonald

[Robert Houllahan]

Different less toxic bleach in processing.

[Joerg Polzfusz]

In Super8, the old TriX is muuuuuch grainier than the new one. No clue whether the differences are also that obvious in 16mm or not.

[Simon Wyss]

Yes, the reversal films got adapted to a potassium permanganate bleach bath instead of a potassium dichromate one.

Let’s hold apart Tri-X reversal, abbreviation TXR, and Tri-X negative film, abbreviated TX by Kodak. Equally Plus-X negative and Plus-X reversal, PXN or PXR

[Christian Flemm]

Thanks all for the commentary - I didn't consider the change from R9 to R10 bleach. Based on looking this up, I see that the original D94 recipe became D94a. D94a added DTOD to the D94 recipe, cut out the Sodium Thiocyanite and replaced the potassium bromide with sodium bromide.

From photrio:

Quote

Here is the old D94 formula:

Kodak D-94

Water, 50 degrees C (125 F) 750 ml
Kodak ELON (Metol) 0.6 g
Sodium Sulfite (anhydrous) 50.0 g
Hyrdoquinone 20.0 g
Potassium Bromide (anhydrous) 8.0 g
(or 7.0 g Sodium Bromide)
Sodium Thiocyanate (liquid) 9.1 ml
Sodium Hydroxide 20.0 g
Water to make 1.0 L

And the new D94A devloper

Kodak D-94A

Water, 50 degrees C (125F) 750ml
Kodak ELON (Metol) 0.6g
Sodium Sulfite (anhydrous) 60.0 g
Hyrdoquinone 20.0 g
Sodium Bromide 7.0g
DTOD 0.42g
Sodium Hydroxide 20.0 g
Water to make 1.0 L

The formulas are pretty similar. There's no Sodium Thiocyanate in the new D-94A, but there is this new DTOD. Sodium Bromide replaces Potassium Bromide, and the amount of Sodium Sulfite is increased.
 

The late filmmaker Robert Fenz claimed that the older emulsion was superior, and benefited from being underexposed by one stop. Travis Wilkerson followed Robert's advice when it came time for him to shoot his film An Injury to One.

Thanks for the help.