I'm interested in DIY photo development and I came across a reversal process that uses chemicals easily available at the grocery store. The purpose of a reversal process is to take a partially developed negative, which is a suspension of silver and silver bromide in gelatin, and turn it into a positive by removing the silver and leaving the silver bromide behind.
The two in question are 3% hydrogen peroxide and 5% acetic acid. I have tried this and it works but I don't understand why.
The process is as follows:
- 30ml of 5% acetic acid solution is added to 500ml of 3% hydrogen peroxide, the rest is just water.
- The mixture is then heated to 60°C.
- In complete darkness the partially developed film is placed in the liquid for 6-10 minutes.
- After this the silver is gone, but a yellow tint is left behind.
- After this the silver bromide is then exposed and redeveloped leaving a positive image.
I believe the tint is silver oxide but I am unsure as I don't know enough about what is actually taking place in this reaction. I'm left with all sorts of questions:
- What reaction is taking place to remove the silver?
- What other reactions might be happening?
- What is the fate of the removed silver after this reaction?
- Why does it need to be hot?
- Why is there a yellow tint left behind? Is it silver oxide or acetate, and how might it be removed/avoided?