Sodium Sulfite clearing bath in ecn2 process

I have been using vision 3 film for about three years. I mix my own chemistry.

Until recently I never used Na Sulfite as a clearing bath after the stop or bleach step. I didn’t see a sulfite clearing step in the protocols published by Kodak. But after reading some old posts that suggested adding sulfite to the stop bath itself I tried it, but as a separate solution of 20g per liter. I also added a clearing step after the bleach. But I was concerned about adding sulfite to the stop solution and the bleach. I use an acetic acid stop and the published ferricyanide bleach formula.

My prior results without clearing worked, but the bleach darkened and didn’t last that long.
With a clearing bath, my bleach hasn’t darkened and I notice a stark improvement in the film results. Mainly the background orange is clearer and lighter. I imagine this was caused by dye buildup in the bleach. The clearing bath after the bleach is probably keeping my fix longer as well by minimizing any bleach getting into the fix.

I just wanted to ask if people do add sulfite directly to the stop solution itself? It was implied in the post but seemed a bit ambiguous. This would cut a step. If so, how much to the stop bath. PE stated that the sulfite should be pH 6.5 which led me to think I shouldn’t add it to the stop itself.

Could one add sulfite to the bleach or would this compromise the bleach?

lawnerd said:

With a clearing bath, my bleach hasn’t darkened and I notice a stark improvement in the film results. Mainly the background orange is clearer and lighter. I imagine this was caused by dye buildup in the bleach.

Click to expand...

The problem is that developer that carries over into the ferricyanide bleach bath instantly oxidizes when the bleach hits it, resulting dye formation at that moment. The additional sulfite bath prevents this.

lawnerd said:

I just wanted to ask if people do add sulfite directly to the stop solution itself?

Click to expand...

No; the problem here would be that the low pH would cause the sulfite to fall apart partly or entirely (depending on the stop bath used) into sulfur dioxide gas. Apart from being rather obnoxious (it's a sharp, prickly smell that irritates mucous membranes and is somewhat dangerous in high concentrations), it means that part or all the sulfite will be lost anyway so it's not very effective.

lawnerd said:

Could one add sulfite to the bleach or would this compromise the bleach?

Click to expand...

This would also not be very effective since it'll be a bit of a contest between the sulfite and the bleach reaching the carried over developer. Some of the bleach will effectively win, causing dye fog as it did before. So you will see some improvement, but not as much as a separate sulfite bath.

If you want to avoid the dye staining issue, you could use a modern C41 bleach instead of a ferricyanide bleach.

Thanks. I would like to use the C41 bleach but I have been unable to source the materials and I don’t want to buy kits for just the bleach.
Ferricyanide is readily available because it is a component of cyanotype.

Yes, ferricyanide is easily accessible and cheap, so I understand its appeal. The (modest) cost it incurs is to have an additional clearing step in the process, but this takes only a minute and a small amount of an even cheaper chemical, so I'd just stick to that approach and not worry about it!

Try my method, which I've personally tested and found to work well with both the ECN2 and C-41 processes (when using Pot Ferri bleach).
This way, you don't have to separate the STOP bath from the Clearing bath.
This is a formula from this forum.

Mixing Instructions for Stop-Clearing Bath for 1 Liter

Ingredients:

- Sodium sulfite: 40g
- Sodium acetate anhydrous: 30g
- Acetic acid (28% solution): 20ml (or approximately 6ml of 99.5% glacial acetic acid)

Remember the rule: Always add acid to water (or solution), never the other way around.

Mixing Order:

1) Prepare the water:

Start with approximately 75% of the final volume of water (e.g., 750ml if the final volume is 1 liter). The water should be at the appropriate temperature to facilitate dissolution (usually around 40°C or 104°F).

2) Add sodium sulfite: Add 40g of sodium sulfite to the water and stir until completely dissolved.

3) Add sodium acetate: Add 30g of anhydrous sodium acetate to the sodium sulfite solution and stir until dissolved.

At this stage, the solution is alkaline, which protects the sodium sulfite.

4) Add acetic acid: Slowly add the calculated amount of acetic acid (20 ml of 28% or 6 ml of 99.5%) to the solution, stirring constantly.

Adding the acid at this stage, when sodium acetate is already present, allows for the immediate formation of an acetate buffer, minimizing the risk of sodium sulfite decomposition.

Add water to final volume and mix thoroughly.

Following this order will ensure the stability of the ingredients and produce a solution with a pH of approximately 5.30.

Spektrum said:

Remember the rule: Always add acid to water (or solution), never the other way around.

Click to expand...

This is a good practice. In reality, nothing happens with acetic acid, if you do the other way around, but with concentrated sulfuric acid, it would be dangerous.

Samu said:

In reality, nothing happens with acetic acid

Click to expand...

Not dilute acetic acid. With glacial (pure) acetic acid, do not add water to the acid! If only because of the risk of splashes.