Kodak Selenium Toner for black and white prints, 946 ml.
What it is for
Selenium does two things at once, and the second matters more. The visible one is tone: depending on paper and dilution the print moves toward cool browns and purples, and the deep shadows gain density. The invisible but decisive one is permanence: selenium converts the metallic silver of the image into a more stable compound, and the print stops fearing time.
How to dilute it
It works across a wide dilution range: strong gives a pronounced tone in minutes, weak gives little more than the archival effect over tens of minutes. Selenium is toxic: gloves and ventilation are required, and spent solution does not go down the sink.
Storage
Sealed concentrate keeps well but dislikes air: the emptier the bottle, the faster it oxidises. Decant the remainder into a smaller bottle, or displace the air — that is what gets a concentrate to its last measure.
How it compares
The most widely used toner in black and white photography, and the one to start with. Sepia shifts more sharply and decoratively; blue goes the other way. Selenium is valued because it can be almost invisible and still do the important job.
