Collodion Negatives: Copper Intensification Control

I've started making collodion negatives for salt printing. I expose them 1.5 to 2 stops more than positives, use a negative developer, and extend the development time. After developing and fixing, I use copper intensification.

While I know from Quinn Jacobson that copper intensification has limited control compared to pyro redevelopment, he also mentioned that some control is possible. How can I better control the density of my negatives using this process? I've also had success getting good contrast with this process, but I want to understand what kind of control I have.

For example, what's the difference in results when I vary the time in the **bleach solution** (Part A & B) , and the time in the **silver nitrate solution**?

I'm using this recipe from Giorgio Bordin:

**Bleach Solution**
* **Part A (20% solution):**
* Distilled water: 100ml
* Copper sulfate: 20g
* **Part B (10% solution):**
* Distilled water: 100ml
* Potassium bromide: 10g

**Intensifier (6% silver nitrate solution):**
* Distilled water: 200ml
* Silver nitrate: 12.5g
* Nitric acid: 3 drops

I haven't been adding nitric acid. What potential problems could this cause?

Thank you in advance!

The amount of time in the silver nitrate isn’t going to make much difference - the full intensification is complete in seconds - but shortening the time in the CuSO4 bath will have a big influence on how much density your negative builds in the silver bath.
Typically, the time in the copper bleach is recommended to be 60-90 seconds, but you can reduce that time to as little as 20 seconds and still get some intensification. But if you intend on using the negatives for processes like Salt printing, you’ll need plenty of density, so bear that in mind when you experiment with the bleach times.

retina_restoration said:

The amount of time in the silver nitrate isn’t going to make much difference - the full intensification is complete in seconds - but shortening the time in the CuSO4 bath will have a big influence on how much density your negative builds in the silver bath.
Typically, the time in the copper bleach is recommended to be 60-90 seconds, but you can reduce that time to as little as 20 seconds and still get some intensification. But if you intend on using the negatives for processes like Salt printing, you’ll need plenty of density, so bear that in mind when you experiment with the bleach times.

Click to expand...

Thank you very much for the detailed advice.

So if I understand correctly, a shorter time in the bleach results in lower density, while a longer time increases the density.


I’ve been trying for around 20–30 seconds and was able to achieve a certain amount of density. I’d like to test longer times—60 seconds or more—to see how that affects the appearance of salt prints.

Is there any detailed manual or reference that describes these processes?

If you know of one, I’d greatly appreciate it.