Collotype
Continuous-tone printing without halftone dots.
A glass plate coated in dichromated gelatin reticulates under UV, holding ink in microscopic patterns that print true continuous tone.
A glass plate coated in light-hardened gelatin holds ink in fine wrinkles, printing photo-quality images without any dot pattern.
- ▸The gelatin dries into invisible micro-cracks that catch ink.
- ▸No screen of dots like in newspapers — tones blend smoothly.
- ▸Slow and fussy, but the results are almost photographic.
History
Alphonse Poitevin patented the process in 1855. Karl Klič and Joseph Albert refined it in the 1860s. Used for fine-art reproductions until offset displaced it; only a handful of workshops still operate today (notably Benrido in Kyoto).
Process
- 01
Coat thick glass with dichromated gelatin and dry.
- 02
Expose under a continuous-tone negative.
- 03
Soak the plate; gelatin swells inversely to exposure.
- 04
Roll oily ink onto the reticulated surface—it sticks where dry.
- 05
Print on a flatbed press onto dampened paper.
Strengths
- +True continuous tone
- +No screen pattern
- +Archival
Limitations
- −Edition limited (~500)
- −Climate-sensitive
- −Few practitioners
Sources & citations
References for the history and process described above.
- 01Collotype Printing — Victoria & Albert Museum
- 02The Atelier of Benrido — Last Collotype Studio — Benrido Collotype Atelier (Kyoto)