Solarization. How to solarize optical printing of black-and-white photographs. Issue 123.
To achieve partial inversion of a photograph, an effect called the "Solarization Effect" is used. A more accurate term would be the "Sabatier Effect." But let's not get bogged down in terminology. We'll simply discuss how we can achieve original photographs with this amazing effect. The strength of the effect depends on the time of the first development, the time of the second exposure, and the photographic paper itself.
I teach film photography classes offline. All the latest information is on VK: https://vk.com/oknophotolab