Patreon for wet plate collodion creators — 2026 edition
Frederick Scott Archer 1851 nitrocellulose collodion ether ethanol chemistry, silver nitrate AgI in-situ sensitization and 5–15 minute working window, pyrogallic acid phenolic reductant versus ferrous sulfate developer tone comparison, sodium thiosulfate Na2S2O3 fixing and argentothiosulfate complex formation, ambrotype glass backing positive versus tintype japanned iron plate, spirit varnish sandarac resin silver film protection, and the Apple Tax.
Wet plate collodion Patreons retain when they deliver the photochemistry and process logic that pour videos and finished-plate galleries structurally compress away: the composition and evaporation sequence of collodion (why ether evaporates before ethanol and what that sequence means for film formation), the in-situ chemistry of silver iodide formation in the sensitization bath (what the potassium iodide dissolved in the collodion is for, and why the silver nitrate bath must be used at a specific concentration), the 5–15 minute working window and what determines its boundaries (solvent evaporation rate, ambient temperature, humidity, and exactly when the film hardens to the point that developer cannot penetrate), the two main developer options at the electron-transfer level (why pyrogallic acid produces warm sepia-brown image tones while ferrous sulfate produces cooler metallic grays, and what the acetic acid in both developers is doing), sodium thiosulfate fixing chemistry (the specific complex that hypo forms with silver iodide, why it is water-soluble and washable while silver iodide is not, and why historical potassium cyanide fixed faster but is not used in modern practice), the ambrotype mechanism (why an underexposed negative on glass viewed against black reads as a positive), the tintype substrate difference (japanned iron rather than glass, and why this made tintypes cheaper and more durable than ambrotypes), varnishing with spirit of sandarac (what resin it uses, why the plate must be heated before application, and what happens to an unvarnished wet plate image over months), and the portable darkroom logistics that define the entire practice.
1. Collodion chemistry and the Frederick Scott Archer process
Frederick Scott Archer published the wet collodion process in 1851, offering it freely without patent. The process was adopted almost universally within a decade and remained the dominant photographic method until the introduction of commercial dry plates in the late 1870s. Its core material is collodion: nitrocellulose (cellulose nitrate) dissolved in a mixture of diethyl ether and ethanol. Nitrocellulose is produced by treating cotton or wood pulp cellulose with a mixture of concentrated nitric and sulfuric acids, forming cellulose nitrate esters at the hydroxyl groups of the glucose units; the degree of substitution is controlled to produce a soluble, film-forming nitrocellulose rather than the more highly substituted guncotton.
The ether/ethanol ratio in collodion affects film behavior. Typical usable collodion for wet plate photography is approximately 2–4% nitrocellulose by weight in a 1:1 to 2:1 ether:ethanol mixture by volume. More ether relative to ethanol increases the initial flow rate (making it easier to coat a plate in one smooth motion), accelerates initial drying, and shortens the working window; more ethanol slows drying and extends the working window at the cost of slower leveling. Diethyl ether boiling point is 34.6°C; ethanol boiling point is 78.4°C. When collodion is poured onto a glass or iron plate and tilted to coat it, ether begins evaporating immediately and preferentially, leaving an increasingly ethanol-rich film. By the time the plate enters the silver nitrate sensitization bath (30–60 seconds after pouring), much of the ether has already escaped, and the collodion film is tacky but still porous enough for the silver nitrate solution to penetrate and react with the potassium iodide dissolved in it.
Potassium iodide (KI) is dissolved in the collodion before the plate is poured, typically at 2–6% by volume in the collodion solution. Its function is to provide iodide ions (I−) that will react with silver nitrate in the sensitization bath to form silver iodide (AgI) within the collodion film. Some collodion formulas include potassium bromide (KBr) at 0.5–2% in addition to potassium iodide; the bromide produces some silver bromide (AgBr), which has slightly higher inherent sensitivity than AgI and extends the effective film speed. Cadmium bromide (CdBr2) was historically used for speed enhancement and is still occasionally used, but cadmium compounds are toxic and require appropriate handling and disposal protocols.
2. Silver nitrate sensitization and the working window
After the collodion is poured and allowed to become tacky (30–90 seconds depending on temperature and ethanol:ether ratio), the plate is lowered face-down into a silver nitrate (AgNO3) sensitization bath. Silver nitrate concentration in modern practice is typically 7–10% by weight in distilled water. The silver nitrate in solution diffuses into the porous collodion film and reacts with the potassium iodide to form silver iodide in situ:
KI + AgNO3 → AgI + KNO3
Silver iodide (AgI) is the photosensitive compound. It is essentially insoluble in water (Ksp = 8.5 × 10−17 at 25°C) and forms as fine crystalline particles within the collodion film. The sensitization bath dip lasts 2–4 minutes; shorter times in warm conditions, longer in cold. The plate is then drained (holding it at 45 degrees for 10–15 seconds) and loaded into the plate holder for exposure. Total time from pour to camera: approximately 3–6 minutes.
The working window — the maximum time between pouring the collodion and completing development — is approximately 10–15 minutes at 20–22°C and moderate relative humidity. At high ambient temperature (28–35°C) the window shrinks to 5–8 minutes because ether evaporation is much faster. At cold temperature (10–15°C) it may extend to 20–25 minutes. As the ether and ethanol evaporate from the exposed plate (outside the sensitization bath), the nitrocellulose film hardens. Once the film has hardened beyond a threshold level, the aqueous developer cannot penetrate it to reach the silver iodide, and no image forms. This is the defining constraint of the entire process: from the moment of pouring to the end of development, the entire operation must be completed within a single window. Document the ambient temperature and working window at the start of each session — this is the first variable that patrons need to understand when their attempts produce nothing.
Effective film speed is approximately ISO 0.5–1 in modern ISO equivalents, though the concept was not used in this form in the 19th century. An ISO 1 collodion plate in bright outdoor sunshine at f/8 requires approximately 1–3 seconds of exposure with a modern coated lens; with period lenses (which transmit less light than modern multi-coated optics) exposures were typically 2–20 seconds outdoors. Indoor or studio portraits required very bright artificial lighting (large oil lamps or early gas-discharge tubes) or direct skylight. The slow speed is a direct consequence of silver iodide having less inherent photosensitivity than the silver bromide used in modern film emulsions.
3. Development: pyrogallic acid versus ferrous sulfate
The two primary developers used in wet plate collodion photography reduce exposed silver iodide to metallic silver by supplying electrons — the fundamental photographic development reaction — but differ in their electron-donation mechanism and the byproducts they produce.
Pyrogallic acid developer (pyro): Pyrogallic acid is 1,2,3-trihydroxybenzene (pyrogallol), chemical formula C6H3(OH)3, molecular weight 126.11 g/mol. It is a phenolic compound in which the three hydroxyl groups on the benzene ring are readily oxidized, donating electrons to adjacent silver ions and reducing AgI to metallic silver:
2 AgI + C6H3(OH)3 → 2 Ag° + 2 HI + C6H2O3 + byproducts
The oxidation byproducts of pyrogallic acid in the presence of silver are a complex mixture of quinones and tanning compounds that stain the collodion film and the silver image itself a warm yellow-orange-brown color. This pyro stain is not a defect — it acts as an additional image density layer in proportion to the amount of development, reinforcing the shadow areas of the image and extending the apparent tonal range of the print beyond what the silver alone would produce. The visual result is a warm sepia-brown image tone that is characteristic of pyro-developed wet plates and distinguishable from neutral black-and-white photographic images. Standard pyro developer formula: dissolve 1–2 g pyrogallic acid in 100 ml distilled water, add 5–10 ml glacial acetic acid (the acetic acid controls the pH and slows the reduction rate, giving more even development across the plate from edge to center). Pour the developer immediately before use — pyrogallic acid oxidizes rapidly in air and a solution mixed hours earlier will be partly exhausted and produce inconsistent results.
Development procedure: pour the developer onto the plate in a smooth motion from one corner, tilting immediately to distribute across the full surface, then tilt continuously in a rocking motion to keep fresh developer contacting the surface. Silver image appears within 5–10 seconds of development start; development is complete when the shadow areas of the image have reached maximum density (typically 15–45 seconds). Wash immediately and thoroughly with water to halt development. Document: developer formula (grams pyro per 100 ml, ml acetic acid per 100 ml), fresh-mixed or time-after-mixing, development time, ambient temperature, wash time. This documentation is the session-to-session reproducibility record.
Ferrous sulfate developer (iron vitriol): Ferrous sulfate (FeSO4·7H2O) reduces silver ions via Fe2+ donating an electron to Ag+:
AgI + FeSO4 → Ag° + FeI2 + SO42− (simplified)
Ferrous sulfate does not produce the warm tanning byproducts of pyro; the result is a cooler, more neutral metallic-gray image tone. The lack of pyro stain means the image density is determined entirely by the amount of metallic silver deposited, which produces somewhat lower apparent maximum density but crisper tonal separation in the midtones. Standard ferrous sulfate developer: dissolve 15–30 g FeSO4·7H2O per 100 ml distilled water, add 10 ml glacial acetic acid per 100 ml water (acetic acid prevents the Fe2+ from oxidizing to Fe3+ in solution and maintains developer activity). Ferrous sulfate developer is more stable than pyrogallic acid in open air and was preferred for outdoor studio and field work in bright conditions where pyro solution deteriorated quickly. Development time is typically 10–30 seconds. Ferrous sulfate developer is less commonly used by contemporary wet plate practitioners, who prefer the tonality of pyro, but it remains the correct choice for very hot conditions or when developer solution will be poured from a container and used over an extended session.
4. Fixing chemistry: sodium thiosulfate and the argentothiosulfate mechanism
After development and washing, the plate still contains unexposed silver iodide scattered through the collodion film — the silver iodide that was not reached by light during camera exposure and thus was not reduced to metallic silver by the developer. This unexposed AgI is sensitive to light and would darken the plate upon exposure to room light if not removed. The fixer dissolves it away.
Sodium thiosulfate (Na2S2O3, commonly called hypo or fixer) reacts with silver iodide to form a water-soluble coordination complex: the argentothiosulfate complex. The primary reaction:
AgI + 2 Na2S2O3 → Na3[Ag(S2O3)2] + NaI
The product Na3[Ag(S2O3)2] (sodium argentodithiosulfate) is water-soluble; thorough washing with water removes it completely from the plate along with the NaI, leaving only the metallic silver image. Sodium thiosulfate was adopted as the standard fixer for photography by John Herschel in 1839, the same year photography was announced, and it remains the basis of modern film and paper fixer chemistry. Concentration in wet plate practice: 15–30 g Na2S2O3 per 100 ml water; fixing time 30–90 seconds for a fresh bath; longer for exhausted fixer. Fixed plates are washed in flowing water for 3–5 minutes.
Historically, potassium cyanide (KCN) was used as a fixer before sodium thiosulfate became the standard. Cyanide forms a soluble complex with silver: AgI + 2KCN → K[Ag(CN)2] + KI. Potassium cyanide is approximately 5× faster acting than sodium thiosulfate. It is also extremely toxic — it is fatal in small doses, and in acid conditions (including common darkroom acids) it releases hydrogen cyanide gas. It is not used in contemporary wet plate practice. Document your fixer chemistry and dilution in every technical Patreon post; patrons who scale recipes incorrectly (too dilute fixer = stained yellow highlights from incompletely removed AgI; too concentrated with excessive soak = silver bleaching from fixer attacking the metallic silver image) need the concentration numbers, not just the chemical names.
5. Ambrotype and tintype: substrate differences and positive image mechanism
The collodion wet plate process as described produces a photographic negative: the areas of the scene that received the most light (highlights) produce the most metallic silver on the plate (dense, opaque areas in the developed image), while shadow areas where little light reached produce little or no silver (thin, transparent areas). Printing from a wet plate negative onto albumen paper or salted paper produces a positive print, following the same logic as modern black-and-white darkroom printing. But two direct positive viewing methods emerged that allowed the wet plate to serve as a finished positive image without printing.
Ambrotype: Underexpose the wet plate negative by 1–2 stops relative to a correctly exposed negative. The resulting developed image has thin, semi-translucent silver deposits in the highlight areas (rather than the dense opaque silver of a correctly exposed negative) and essentially no silver in the shadow areas. When this underexposed negative is viewed against a black backing — black velvet, black paper placed behind the glass, or black japan lacquer painted directly on the reverse surface of the glass — the optical result is reversed. The thin silver in highlight areas reflects light and appears bright against the black background; the clear glass in shadow areas transmits light to the black backing and appears dark. The image reads as a positive. The ambrotype was typically housed in a case (hinged case with velvet or silk lining, similar to a daguerreotype case) and viewed under reflected light. It cannot be printed from. Each ambrotype is a unique object. The name derives from the Greek αμβροτοσ (ambrotos), meaning immortal — an early marketing claim that collodion images on glass would last indefinitely.
Tintype (ferrotype): The same collodion chemistry is applied to a thin iron plate (typically 26–28 gauge black iron sheet) pre-coated with a black japanned lacquer. Japan lacquer is an asphalt-based or lampblack-based coating applied and baked onto the iron; the resulting surface is smooth, black, and chemically compatible with the collodion. The japan coating serves the same optical function as the black backing on an ambrotype: thin silver in highlight areas appears bright against the black substrate; unexposed (or shadow) areas where no silver was deposited appear black from the japan surface. The tintype produces a direct positive image on the iron plate without any separate backing operation. Tintypes were cut with tin shears (metal shears — the source of the “tin” in tintype, despite the substrate being iron), allowing them to be immediately trimmed and handed to portrait subjects. Tintypes are more durable than glass ambrotypes, less susceptible to breakage, and required no case. They could be produced in very large numbers quickly and cheaply, making wet plate portraiture accessible to a much wider clientele. Tintype production dominated commercial portrait studios until gelatin dry plates and eventually roll film replaced the wet plate.
Daguerreotype comparison — a question patrons frequently ask: the daguerreotype (Louis Daguerre, 1839, announced publicly the same year as Herschel’s thiosulfate fixer work) uses a fundamentally different chemistry. The substrate is a polished silver-plated copper plate exposed to iodine vapor to form silver iodide on its surface; after exposure in the camera, the plate is developed by exposing it to mercury vapor at 75–80°C, which amalgamates preferentially with the metallic silver formed at exposed AgI sites, building up a bright mercury-silver amalgam in highlight areas while shadow areas retain the unamalgamated silver iodide (which is then fixed with sodium thiosulfate). The daguerreotype produces an image of extraordinary resolution and tonal delicacy, but it is a unique specular positive — the image is invisible from most angles and only visible when the plate is tilted to the correct viewing angle, at which point it appears as a positive. Unlike the wet plate negative, a daguerreotype cannot be contact-printed. Daguerreotypes were also much slower than wet plates (ISO ~0.01–0.1 equivalents with early f/3.6 Petzval portrait lenses), and mercury vapor is highly toxic. Wet plate collodion largely displaced the daguerreotype by the mid-1850s because collodion plates were faster, cheaper per image, and produced a printable negative.
6. Varnishing and long-term stability
A fixed and washed wet plate collodion image, without varnishing, is fragile and subject to two primary failure modes. First, the collodion film itself, now a thin layer of nitrocellulose with embedded metallic silver, is physically fragile: it can be scratched by anything that contacts the surface, and the edges may lift from the glass or iron substrate, particularly at corners where the collodion pulled during drying. Second, the metallic silver image oxidizes over months in contact with sulfur compounds in the atmosphere, the same tarnishing process that darkens unprotected silver metal; the silver image gradually loses density and becomes veiled with silver sulfide.
Varnishing with a spirit varnish addresses both failure modes. The traditional varnish is a solution of sandarac resin (a natural resin derived from the dried secretions of the Callitris quadrivalvis tree, also called sandarach or Tetraclinis articulata) dissolved in denatured alcohol at approximately 5–15% by weight. Application procedure: heat the finished, dry plate over an alcohol lamp flame or on a warming plate until it is too hot to hold comfortably against the skin (approximately 50–70°C — the plate should be visibly warm to an IR thermometer; insufficient heating produces a varnish that does not flow or bond properly). Immediately pour a small amount of sandarac spirit varnish onto the center of the heated plate, tilt and swirl to distribute it evenly across the entire surface to the edges, then tilt and pour off excess. The alcohol carrier evaporates almost immediately on contact with the hot plate surface, leaving the sandarac resin as a thin, hard, transparent film over the collodion. The resin provides a physical barrier against scratching and seals the silver surface from atmospheric sulfur contact. Document: varnish composition (sandarac vs other resin options), concentration, plate temperature at application, and whether any areas were missed (varnish appearance changes from glassy to slightly hazy in areas that were too cool when varnish was applied, requiring reheating and re-application).
Alternative resins used in spirit varnishes for wet plate: copal dissolved in turpentine or naphtha (harder and slower-setting than sandarac; less commonly used for wet plate), damar resin in turpentine (softer than sandarac), or commercially prepared photographic plate varnishes formulated for wet plate work. All require the same heated-plate application procedure. An unvarnished wet plate image is archivally unstable and should not be considered finished. For tintype images that will be displayed in frames or used frequently (handled by multiple people at portrait studios), varnish also protects the image from the slightly acidic moisture of fingerprints.
7. Portable darkroom and field logistics
The 5–15 minute working window of wet plate collodion requires that all processing steps — pouring, sensitizing, exposing, developing, fixing — occur within a single darkroom space located close to the camera. For studio work this is straightforward: a permanent darkroom adjacent to the studio is normal. For outdoor field photography (landscape, portraiture in locations, documentation photography for engineering or architecture, war correspondence), the entire darkroom must travel with the photographer.
The traveling darkroom took two main forms in the 19th century and is replicated by contemporary wet plate photographers working in the field. The darkroom wagon (or darkroom cart) is a small horse-drawn vehicle fitted with shelves for chemicals, a water tank, a light-tight interior workspace, and a red-glass or orange-glass light source (red and orange light does not expose silver iodide, which is primarily sensitive to ultraviolet and blue light). The collodion is poured and the plate is sensitized and loaded in the wagon; the photographer carries the loaded plate holder to the camera for exposure, then runs the plate back to the wagon for development. Distance from wagon to camera should be minimized — typically 30 meters or less for a 12-minute window at 20°C. The darkroom tent is a lighter-weight version: a black-fabric tent, sometimes with one person inside, that serves as the light-tight environment for pouring and processing. Contemporary field wet plate photographers use both types and have additionally designed portable darkroom boxes (essentially light-tight chests with built-in chemical storage and a small working surface) that fit in the back of a vehicle.
For Patreon documentation purposes: describe your field setup (wagon, tent, box, or studio adjacent) and the specific logistics of working at the edge of the working window in field conditions. The procedural reasoning behind the distance from camera to darkroom, the chemical storage order, the plate-handling sequence, and the technique for keeping the plate cool enough to extend the window in hot weather (chilling the plate holder, working in shade, pouring thicker collodion for slower drying) are exactly the production layer that field-portrait videos compress into a single “working outside” shot.
8. Apple Tax
Wet plate collodion content reaches iOS audiences at high rates across platforms. YouTube wet plate process documentation, behind-the-scenes of field sessions, and finished-plate reveals reaches 60–75% iOS; some desktop share from photographic history students and educators watching in academic settings pushes this slightly lower than pure craft niches. Instagram wet plate and collodion photography reaches 75–85% iOS; the distinctive high-contrast textured aesthetic of collodion images performs extremely well in Instagram’s visual format and the audience is almost entirely mobile. TikTok collodion pour and development reveal content reaches 75–85% iOS.
At $200/month from a YouTube-primary creator at 65% iOS: $39/month ($468/year) lost to Apple after November 1, 2026. At $300/month from a mixed YouTube and Instagram audience at 72% iOS: $64.80/month ($777.60/year). At $500/month from an Instagram-primary creator at 80% iOS: $120/month ($1,440/year). Enable Patreon’s web-only billing toggle before October 31, 2026 and direct all platform bio links to the Patreon web URL to remove Apple’s 30% fee from web-subscribing patrons.