Sepia Toning
A chemical treatment that converts a print's metallic silver into silver sulphide, producing warm brown tones.
In depth
The process bleaches the image back to a faint yellow, then redevelops it in a sulphide toner. Beyond the colour change, silver sulphide is considerably more stable than metallic silver, so sepia toning is genuinely archival — which is one reason so many Victorian prints survive in good condition.
Examples in practice
A bleached and redeveloped print emerges a rich brown, with slightly reduced density in the deepest shadows.