12-14 years ago , I had ben opened a thread about palladium toning of 6X24 positive BW Film.
That might have been this thread:
https://www.photrio.com/forum/threads/palladium-toning-of-bw-negatives-and-its-effect.118346/
Why would you want to tone film in palladium?
3- Can I buy 0.1 grams of palladium from jewelry center ?
Note that you wouldn't be buying metallic palladium, but rather a palladium salt that's soluble in water, like palladium chloride. A jeweler typically won't stock this material as it has no common/practical use in that application. You can find sellers of palladium salts like palladium chloride online. You might try eBay or if you're willing to import from the US, companies like Bostick & Sullivan:
https://www.bostick-sullivan.com/product/palladium-chloride-powder-1-gram/
Btw, 0.1g isn't going to get you very far:
1- How much palladium should be used to tone 120 positive developed roll ?
That's an interesting question. Assume film has a silver content of 3-5g/m2. A roll of 120 film is ca. 6x84cm so roughly 500cm2. Let's assume that roughly half the silver remains in the film when processed as a positive (this is a crude assumption). This means you have something along the lines of 0.1g - 0.15g of metallic silver left on your processed film. Palladium will act as a metal replacement toner, replacing the actual silver. The ratio will be equimolar, so one mole of silver will be replaced by one mole of palladium. Assuming you start with palladium chloride, the ratio in molar mass between silver and PdCl2 will be around 1:1.7. So toning the film to completion would take something like 0.15-0.25g of palladium chloride.
One thing works to your advantage, which is that you probably won't have to tone entirely to completion. You may only want to tone something like 25%-50% depending on the effect you're after. So that would limit the amount of palladium chloride you need.
On the other hand, what works against you is that the efficiency of the toning process will never be complete; there will always be a little unreacted palladium left in the spent toning solution. Toning gets horribly slow at some point because simply put, the rare palladium ions in the solution won't easily find a silver molecule to replace on the film; as the toning solution depletes, these odds grow slimmer and the toner becomes exponentially slower.
2- What is the cheapest solution formula to do palladium toning and least amount of use palladium ?
The common compound used is palladium chloride as pointed out above. The cheapest approach is to use a minimal volume of toner that contains just enough palladium to accomplish the toning you want. For roll film, this means you would use some kind of bath/container/tray that you can very efficiently dunk the film in, or perhaps pull it through in a see-saw fashion. You could also try a rotary drum, although this will usually take something like 200ml or more of toning solution.
Overall, if you're looking to give the positive images on the film a warm hue, I'd suggest sepia toning, which is extremely cheap and very easy to do.
