Historical Photography Processes - Quick Reference Lexicon
Compiled: 2026-05-23 Purpose: Quick reference for identifying and understanding historical photographic processes from 1839 to present
Direct Positive Processes (No Negative)
Daguerreotype (1839-1860s)
What: First commercial photographic process Material: Silver-plated copper plate, mercury vapor development Appearance: Mirror-like surface, image appears/disappears with viewing angle Identification: Cased, extremely fine detail, unique (one-of-a-kind) Handling: NEVER touch surface - any contact damages the image Storage: Keep original seal intact, climate-controlled environment
Ambrotype (1854-1880s)
What: Underexposed glass negative + black backing Material: Collodion on glass Appearance: Positive image when backed, negative when held to light Identification: Lighter/grainier than daguerreotype, often cased Common Use: Cheaper alternative to daguerreotype Hazard: Glass fragile, emulsion can peel
Tintype / Ferrotype (1856-1930s)
What: Collodion emulsion on thin iron plate Material: Japanned iron base Appearance: Dark, slightly flexible, magnetic Identification: Test with magnet, laterally reversed Durability: Most stable of cased images if kept dry Hazard: Rust if exposed to moisture
Negative Processes
Calotype / Talbotype (1841-1860s)
What: First practical negative-positive process Material: Paper negative Appearance: Waxed paper, visible paper texture in prints Advantage: Multiple prints from one negative Disadvantage: Paper grain limits sharpness
Wet Collodion Plate (1851-1880s)
What: Glass plate coated with collodion, exposed while wet Material: Glass base, collodion emulsion Appearance: Yellowish-brown color, excellent detail Workflow: Prepare - Sensitize - Expose - Develop (all within minutes) Challenge: Required portable darkroom for field photography
Gelatin Dry Plate (1871-1990s)
What: Factory-made glass negatives Material: Glass + gelatin silver halide Appearance: Gray/neutral color, emulsion on one side Advantage: Could be stored before use (revolutionary!) Standard: Dominant from 1880s until roll film Storage: Vertical like books, individual envelopes, never stack flat
Nitrate Film (1889-1951)
What: First flexible film Material: Cellulose nitrate base DANGER: Highly flammable, self-ignites at 40°C (104°F) Identification: "Nitrate" printed on edge, camphor-like smell Degradation: Becomes sticky, releases toxic nitrogen dioxide gas Action: Duplicate to safety film ASAP, destroy original safely
Acetate Film (1923-1990s)
What: "Safety film" replacement for nitrate Material: Cellulose acetate base Problem: "Vinegar syndrome" - releases acetic acid as it degrades Identification: Vinegar smell, warping, shrinkage, brittleness Storage: Cool, dry, isolated from good film
Polyester Film (1960s-present)
What: Modern stable film base Material: Polyester (PET) Stability: Extremely stable, archival when properly processed Standard: Current film manufacturing
Positive Print Processes
Salt Print (1840-1860s)
What: Earliest paper print process Material: Salted paper + silver nitrate Appearance: Matte surface, reddish-brown tones Character: Image sits in paper fibers (not on surface) Fading: Prone to fading without gold toning
Albumen Print (1850-1900)
What: Most common 19th-century print process Material: Egg white (albumen) coating + silver Appearance: Glossy surface, yellowed highlights Identification: Rich brown tones if gold-toned, typical on thick card mounts Degradation: Inevitable yellowing (albumen ages to brown), cracking Fact: Peak production consumed millions of eggs annually
Platinum / Palladium Print (1880s-1930s)
What: Noble metal print process Material: Platinum or palladium metal (not silver) Appearance: Subtle tonal gradation, embedded in paper fibers Stability: Extremely stable, museum-quality longevity Color: Cool gray (platinum) or warm gray (palladium) Cost: Expensive even when invented, luxury today
Carbon Print (1864-1930s)
What: Pigmented gelatin image Material: Pigment + dichromated gelatin Appearance: Rich, velvety blacks Stability: Permanent (pigment doesn't fade like silver) Colors: Any pigment color possible Use: Fine art reproduction, photomechanical printing
Cyanotype (1842-present)
What: Iron-based blueprint process Material: Ferric ammonium citrate + potassium ferricyanide Appearance: Unmistakable blue (Prussian blue) Identification: Cyan color on paper Use: Architectural plans (blueprints), artistic prints Quirk: Fades in light but regenerates in darkness
Gelatin Silver Print (1880s-present)
What: Standard modern B&W photograph Material: Gelatin + silver halide on paper Appearance: Neutral black, matte to glossy finish Types: - Developing-Out Paper (DOP) - Modern prints - Printing-Out Paper (POP) - Self-printing in sunlight (rare after 1920) Stability: Excellent if properly processed and stored Degradation: Silver mirroring (humidity + pollutants), fading (poor washing)
Chromogenic Color Print (1942-present)
What: Modern color photograph Material: Dye couplers + silver halides Appearance: Full color Processes: C-print (negative), R-print (reversal/slide) Stability: Fades over time, especially in light Note: Not a "historical" process but included for completeness
Standard Historical Formats
Portrait Formats (1850s-1910s)
| Format | Size (cm) | Size (inches) | Era | Use |
|---|---|---|---|---|
| Carte-de-Visite (CDV) | 10 × 6 | 4 × 2.5 | 1854-1890s | Visiting cards, albums |
| Cabinet Card | 16.5 × 10.8 | 6.5 × 4.25 | 1866-1910s | Portraits, replaced CDV |
| Imperial | 25 × 18 | 10 × 7 | 1860s-1900s | Large portraits |
| Boudoir | 21.6 × 13.3 | 8.5 × 5.25 | 1870s-1900s | Intimate portraits |
| Stereograph | 17.8 × 8.9 | 7 × 3.5 | 1850s-1930s | 3D viewing (twin images) |
Plate Sizes
Whole Plate: 21.5 × 16.5 cm (8.5 × 6.5 inches) Half Plate: 16.5 × 10.8 cm Quarter Plate: 10.8 × 8.3 cm Sixth Plate: 8.3 × 7 cm Ninth Plate: 5.7 × 5.1 cm
Conservation Quick Reference
The Enemy Trinity
- Light - Fading, discoloration, embrittlement
- Heat - Accelerated chemical degradation
- Humidity - Mold, oxidation, adhesion
Optimal Storage
- Temperature: 15-20°C (59-68°F)
- Relative Humidity: 30-40% (strict control!)
- Light: Darkness when not displayed
- Materials: Acid-free, lignin-free paper/board
Quick Rules
DO: - Wash hands before handling - Use cotton gloves for metal/glass - Store in stable environment - Use acid-free materials - Interleave stacked items
DON'T: - Touch image surface - Use rubber bands or paper clips - Store in basements (humid) or attics (hot) - Use PVC plastic ("vinyl") - Expose to direct sunlight
Damage Types at a Glance
| Symptom | Cause | Process Affected |
|---|---|---|
| Yellowing | Albumen aging, acidic materials | Albumen prints, paper |
| Silver Mirroring | Humidity + sulfur | Gelatin silver prints |
| Fading | Light, poor fixing | All silver processes |
| Vinegar Smell | Acetate degradation | Safety film |
| Rust | Moisture | Tintypes |
| Cracking | Low humidity, temp cycling | Albumen, gelatin emulsions |
| Mold | High humidity (>60%) | All organic materials |
Key Chemistry Terms
Silver Compounds (Most Processes)
- AgNO₃ (Silver Nitrate) - Light sensitizer
- AgCl (Silver Chloride) - Printing-out papers
- AgBr (Silver Bromide) - Film, developing-out papers
- Na₂S₂O₃ ("Hypo") - Fixer, removes unexposed silver
Development
- Pyrogallol - Early developer (wet plate era)
- Hydroquinone - Modern developer
- Metol - Fast-acting developer
Toning
- Gold Chloride - Increases longevity, purple-brown tones
- Selenium - Protective toning for modern prints
- Sulfide - Sepia tones, increased stability
Quick Identification Guide
By Appearance
Mirror-like surface, in case: - Daguerreotype (1839-1860s)
Glass, black backing, in case: - Ambrotype (1854-1880s)
Metal, magnetic, not in case: - Tintype (1856-1930s)
Glossy, yellowed highlights, on thick card: - Albumen print (1850-1900)
Unmistakable blue color: - Cyanotype (1842-present)
Velvety blacks, embedded in paper: - Platinum print (1880s-1930s)
Neutral black/gray, modern look: - Gelatin silver print (1880s-present)
Glass negative, yellowish: - Wet collodion (1851-1880s)
Glass negative, gray: - Dry plate (1871-1990s)
Flexible film, camphor smell: - Nitrate film (1889-1951) - DANGER!
Flexible film, vinegar smell: - Acetate film (1923-1990s) - degrading
Timeline at a Glance
| Year | Innovation |
|---|---|
| 1839 | Daguerreotype announced (Daguerre) |
| 1841 | Calotype patented (Talbot) - first negative |
| 1842 | Cyanotype invented (Herschel) |
| 1850 | Albumen paper introduced |
| 1851 | Wet collodion process (Archer) |
| 1854 | Ambrotype introduced |
| 1856 | Tintype/Ferrotype introduced |
| 1871 | Gelatin dry plate (Maddox) - game changer |
| 1880s | Gelatin silver printing paper standard |
| 1888 | Kodak #1 camera - "You press the button, we do the rest" |
| 1889 | Nitrate roll film (Kodak) |
| 1900 | Brownie camera - photography for the masses |
| 1935 | Kodachrome (first practical color film) |
| 1951 | Nitrate film production ends |
| 1960s | Polyester film base introduced |
| 2000s | Digital photography becomes dominant |
When to Consult a Conservator
DIY (Safe for Beginners): - Re-housing in acid-free materials - Basic cleaning (dust removal with soft brush) - Creating access copies (scans) - Environmental control (climate monitoring)
EXPERT REQUIRED: - Stuck-together photographs (DO NOT force apart) - Mold/fungus (health hazard + delicate treatment) - Torn emulsions - Chemical restoration/toning - Daguerreotype cleaning (extremely delicate) - Nitrate film handling (safety issue)
Essential Reading
Identification: - Reilly, James M. "Care and Identification of 19th-Century Photographic Prints" (1986)
Conservation: - Lavédrine, Bertrand. "Photographs of the Past: Process and Preservation" (2009)
Technical/Historical: - Crawford, William. "The Keepers of Light" (1979) - working guide to historical processes
Online: - Graphics Atlas: http://www.graphicsatlas.org (process identification) - AIC (American Institute for Conservation): https://www.culturalheritage.org
Key Takeaways
- Every photograph degrades from birth - proper storage slows it down
- Know the process - identification guides conservation decisions
- Enemy trinity: Light + Heat + Humidity = destruction
- When in doubt, don't - consult a professional conservator
- Digitize for access - handle copies, preserve originals
- Acid-free is key - use proper archival materials
- Nitrate film = DANGER - isolate and duplicate immediately
Sources: - International museum and conservation archives - Photographic conservation literature - Historical process documentation
Compiled: 2026-05-23 Purpose: Quick reference for photo identification and basic conservation
"Photography is the only art form so closely tied to its technology - technical development enabled its birth and will cause its end."