A brief intro

Historical bullet points

Historical bullet points (II)

Historical bullet points (III)

General qualities of carbon prints

• optimal permanence
• ideal linear characteristic curve
• textured surface ("relief")
• variety of pigments
• variety of final supports

A pioneer: Julia Margaret Cameron

What you need to make a carbon print

The negative

Silver gelatine negative (slice, side view)

Transmission density profile:

Glop

Carbon tissue

i.e. the "photosensitive paper"

Pouring tissue

Making a carbon print

Exposure

Neg + tissue sandwich exposed to UV

(contact printing only; no enlargement)

Post-exposure

The exposed parts have hardened (top-down according to common lore)

Mating

The exposed tissue (flipped) is mated with a final paper support

Development

Tissue/paper sandwich plunged in hot (40C) water

The tissue support is peeled away

The non-hardened glop melts away

The hardened part adheres to the final paper support

Post-development

The result is hardened gelatine with embedded ink,

on an archival paper support

producing the final photographic image

Single transfer

Double transfer

Multiple transfer

A more advanced method making use of multiple transfers onto a temporary support

Problems and pitfalls

Carbon transfer is perhaps the most

finicky traditional photographic process

• highlight loss (percolation threshold?)
• bubbles (from water, Nitrogen)
• adherence (flagging, frilling, delamination)
• exposure control
• contrast control

Factors affecting the process

• gelatine composition
• ink type/concentration
• sensitizer type/concentration
• light source
• exposure
• support type (adherence)
• mating bath (temp, duration)
• development bath (temp, duration, agitation)

From practice to theory

My objective: to understand

the "microscopics" of the process

• photoinduced cross-linking
• interplay between constituents
• dynamics of development

Gelatine

Gelatine composition: 19 amino acids

• glycine (Gly) 26-34% – promotes close packing
• proline (Pro) 10-18% – inhibits conformation
• hydroxyproline (Hyp) 7-15%
• alanine (Ala) 8-11%
• arginine (Arg) 8-9%
• aspartic acid (Asp) 6-7%
• glutamic acid (Glu) 10-12%

Glycine

C₂H₅NO₂

Sensitizers

Dichromates

Diazidostilbene (DAS)

Disodium 4,4'-diazidostilbene-2,2'-disulfonate tetrahydrate

PubChem

Use for carbon transfer:

Charles Berger, Richard Kauffman

(1993, UltraStable process)

Diazidostilbene

Research literature

Further links: gelatine, cross-linking, organic azides etc

Modelling the process

Cross-linking

Step-growth or chain-growth?

• Carothers equation
• Flory-Stockmayer theory
• Random graph theory of gelation (Paul Erdős and Alfréd Rényi)

Physical properties as function of degree of hardening?

Spherical cow

M1 model

Following up

Any help or suggestion welcome!