Anthotype

What It Is

Anthotype printing uses the photo-sensitivity of plant pigments — most plant colours fade when exposed to prolonged UV light. A contact negative or stencil is placed over a paper or fabric coated with plant pigment extract, then exposed in sunlight for days to weeks. The UV light bleaches the exposed areas; protected areas retain the original colour.

The process was first described by Sir John Herschel in 1842 (the same year as cyanotype), but largely forgotten until revived by contemporary artists interested in eco-photography and alternative process.

Pigment Sources

From the San Casciano workshop (Almudena Romero, Day 1 afternoon, 2025):

• Spirulina (스피룰리나): Deep blue-green. Mix as 1:4 (spirulina:water or alcohol). Alcohol extraction produces stronger colour. Good UV sensitivity — fades to near-white in exposed areas.
• Turmeric / Curcuma (강황): Bright yellow-orange. Highly pH-sensitive — shifts dramatically with acid/alkaline treatment after exposure. Fix with borax (sodium borate) bath to stabilize. Sodium carbonate (soda ash) bath produces a strong colour shift. Highly fugitive without fixing.
• Red cabbage (적양배추): Purple-blue. Extremely pH-sensitive — functions as a natural pH indicator (red in acid, purple in neutral, green/yellow in alkaline). Beautiful but very fugitive. Best used for process-based or time-based work.
• Beetroot (비트): Deep red-purple. Moderate UV sensitivity. Tends toward brown on fully exposed areas.
• Hollyhock / Hibiscus: Pink to mauve. pH-sensitive.
• Poke berry (포크베리): Dark red-purple. Medicinal berry — dye.

Extraction Methods

• Water extraction: Simmer plant material gently, strain. Works for most pigments.
• Alcohol extraction (에탄올): Soak in 70-96% ethanol — extracts pigment more efficiently and stays on paper surface (rather than penetrating fibres as water does). Preferred for delicate pigments like spirulina.
• Ratio: Concentrate the extract — the stronger the pigment, the longer the image will last.

Binding Agents

The pigment extract must adhere to the paper or fabric surface:

• Plain extract (no binder) — works on sizing-free paper; may bleed into fibres
• Gum arabic or alginate added to the extract — improves surface coating and reduces bleed
• Soy milk pre-treatment on fabric — the protein layer helps plant pigments adhere to cotton or silk

Exposure

• UV index as high as possible, direct sunlight
• Exposure time: 1–7 days depending on pigment concentration and UV conditions
• Use a contact printing frame or glass + weight for full contact
• Check progress without disrupting alignment

Fixing

Anthotype prints are inherently fugitive — all plant pigments will eventually fade. Partial fixing strategies:

• Turmeric: Borax (붕사) bath — a borax sodium borate solution stabilizes turmeric anthotypes significantly. The Day 4 San Casciano session included borax fixing as the final step. This is one of the most effective natural fixatives for anthotype.
• Sodium carbonate bath: Shifts turmeric color dramatically (yellow → orange-red in alkaline) and can partially fix.
• Store in the dark — the single most effective preservation method for all anthotypes.
• UV-blocking framing glazing — extends display life significantly.

Common Failures

• No image appears: Insufficient UV, too-weak pigment extract, or transparent negative (needs dark areas to block UV).
• Entire print fades uniformly: Negative was not in full contact, or UV came from multiple angles. Ensure single-direction UV source.
• Colour shifts unexpectedly: pH change from handling or atmospheric moisture. Normal for pH-sensitive dyes — use as a feature.

Jay's Studio Note

The San Casciano workshop (Almudena Romero, Day 1 afternoon) introduced anthotype alongside chlorophyll printing as a reminder that photography does not require chemistry — only light and time, and the willingness to accept that the image will change. The turmeric anthotypes made that afternoon were fixed with borax on Day 4 — watching the shift from process (exposed, unfixed) to archive (fixed, stored) made the impermanence of the medium tangible rather than theoretical.

Related Materials

Chlorophyll Printing · Cyanotype · Lumen Print · pH & Colour

References

• Almudena Romero — anthotype workshop, San Casciano, Tuscany, 2025
• Sir John Herschel — anthotype process, 1842