Unblinking Eye
WetplateBannerL

 

 Return to Previous Page of Wetplate Collodion Photography

Preparation of the Plate

Fig. 14  The ambrotype effect.

Japanned metal plates (steel sheets coated with baked ashpaltum) were used historically to create inexpensive positive collodion images known as “tintypes” or more properly, “ferrotypes.”  While Civil War Reenactors strive to attain period correctness in equipment and materials by making genuine ferrotypes, preparation of authentic japanned plates is time-consuming and messy.  As a result, many modern wetplaters use prepared black -enameled sheets of aluminum as the image substrate.  Extremely convenient and inexpensive, the aluminum plates can be cut to size by suppliers such as Main Trophy Supply.  The aluminum plates have a thin cellophane-like cover that is peeled immediately before pouring the collodion.  This greatly reduces dust and resultant artifacts on the finished plates.  Due to the thinness of the material, images made on metal sheets are generally backed by a “tablet” of glass in the plate holder.  This glass backing-sheet prevents the spring holding the collodion plate to the focal plane from bending the metal sheet and throwing it out of focus.

Fig. 15  A handle-mount glass cutter and glass pliers recommended for dimensioning glass plates.

Sheets of glass are also used to make positive collodion images known as ambrotypes, as well as glass negatives from which prints can be made.  The difference between the two variations depends on the density of the image.  Ambrotypes are really underexposed collodion negatives that reverse their tonality when backed by a dark material or when made on dark colored glass (i.e., “ruby ambrotypes,” Figure 14).  Collodion negatives and positives are virtually grainless.

The initial preparation of the glass involves cutting the plates to size and then sanding or using a whetstone to dull the edges of the plate (Figure 15).  The roughening should result in an approximate angle of 45 for the glass edge around the surface to be coated.  This abrasion serves two purposes.

 

 

 

 

 

 

First, it minimizes the hazard of cutting the skin on sharp edges of glass. (And this is particularly important to avoid if the photographer uses potassium cyanide as the fixer.  Sharp or broken glass and a lethal chemical is a recipe for disaster.  Additionally, if potassium cyanide is used as the fixer, it should never be stored in glass containers.)  Second, the roughened edge helps adhere the collodion to the slick glass surface.

The glass used for ambrotypes or negatives must be immaculately clean in order to prevent image artifacts and peeling of the film.  The glass is typically cleaned using a solution comprised of whiting or rottenstone (both varieties of fine calcium carbonate) mixed in a solution of alcohol and water .  A bit of solution is poured onto the plate and rubbed around to remove oil and dirt on the glass.  Care must be taken to remove all traces of this alkaline cleaning solution to prevent contamination of the expensive silver nitrate sensitizing solution.  I like to use small lintless PEC Pads to clean the plates.  These special pads will clean many plates before they need to be discarded.

Some collodion formulas containing cadmium bromide and/or cadmium iodide are tender and tend to lift from the surface of the plate.  Adding a subbing to the surface helps prevent this defect.  The most common subbing is egg albumen mixed with a small amount of water and spread about 1/8” in from the edge of the plate with a cotton swab.

Immediately before coating the glass plate with collodion, the surface should be brushed to remove ubiquitous dust.


Pouring the Collodion

The use of thin, chemically-resistant gloves is strongly recommended when pouring the collodion, in subsequent steps involving sensitizing the plate in silver nitrate, and additionally throughout the development process.  Wetplate is historically referred to as “The Black Art” due to the silver nitrate stains that identified early practitioners.  In addition to the staining potential, silver nitrate is corrosive and may cause blindness if concentrated solutions are accidentally splashed into the eyes.  Because of these hazards, the use of chemically resistant gloves and protective goggles is recommended when handling this chemical.

Pouring the collodion properly is a skill that comes with some practice.  Novice wetplaters have a tendency to use insufficient collodion solution in their initial pours.  Too little solution causes irregular coatings and blank “islands” lacking emulsion on the finished plates.   It is far better to use too much collodion and have some spill over the edge of the plate than to use too little.

Collodion has the approximate viscosity of warm maple syrup or cream and practice with such a substance can safely and inexpensively facilitate the learning process.

Pouring the collodion can be done in normal illumination in proximity to the darkroom or darkbox.  However, I find it easier to pour in the darkbox.

To pour the collodion properly, the plate is held as horizontal as possible using one of several methods.  For small plates, it is probably easiest to pinch one corner between thumb and forefinger and pour the solution with the other hand.  For moderate size plates, the “waiter tray” method supporting the plate from below may be best approach (Figure 16). 
Photo by Bill Schwab

Fig. 16  The “waiter tray” method.

With larger, heavier plates, a combination of one of the two previous methods while supporting the opposite corner on a table may be required.

When coating the surface should have a fairly large pancake-like pour of collodion in the center of the level plate.  The plate is then gently inclined towards the photographer so that the fluid moves towards the near corner without flowing off the edge or touching the fingers holding the plate.  Once the near corner is covered sufficiently, the plate is gently inclined to the adjacent nearest corner, then downward to the third corner, and finally to the “pour-off” corner.  As the fluid approaches the last corner, the plate is quickly turned near vertical with the final corner placed inside a vessel used for containing the solution.   The plate is rocked back and forth while the collodion drains into the collection bottle.  This helps minimize lineations and irregular thicknesses in the collodion film.  The entire coating operation should only take a few seconds to complete.  With larger plates, it may be necessary to add additional solvent (ether or grain alcohol) to the formula in order to facilitate pouring and delay the setting up of the collodion film prematurely.  You’ll notice that solvents are continuously evaporating from the plate once the pour begins.  Evidence for this evaporation is found in the obvious ethereal fumes and the rapid cooling of the plate in hand.


Ether Hazard

To minimize the evaporation of solvents from the storage vessel, be sure to cap the bottles as soon as possible.  Also, be sure to perform this coating step far away from any flame or ignition source as the collodion/ether fumes when concentrated can be dangerously explosive.  Ether has a low flash point and becomes ignitable at concentrations as small as 1.9% of the total air volume.  Use the collodion only in well-ventilated areas (outdoors or indoors with proper explosion-proof ventilation systems specifically engineered to safely eliminate volatile hazardous fumes).  Ether is also heavier than air and so fumes may sink to the ground surface and travel some distance before dissipating.  For this reason, it is imperative to store and handle ether and collodion away from ignition sources such as water heaters, furnaces, surfaces radiating heat, electric fans and other devices which may produce an ignition spark.  Store these solutions outside of residences in cool, dark, and preferably explosion-proof cabinets or special laboratory refrigerators.

It should also be noted that while the collodion and ether have a longer shelf life when refrigerated, such storage should only be done in explosion-proof refrigerators.  Regular household refrigerators should not be used to store these potentially-explosive chemicals.  Should fumes accumulate, any spark from the fan motor may ignite the concentrated fumes and cause an explosion.

Also, because of its potential to form explosive peroxides, opened bottles of ether should be disposed of as soon as possible.  Industrial and institutional guidelines generally recommend disposal of ether within 3-6 months of opening under optimum storage conditions.  This assumes oxygen within the container has been minimized using glass marbles to displace any air within the storage vessel or by using a gas blanket specifically employed and formulated to displace air from the surface of the volatile fluid.  Any ether stored beyond this timeframe should be considered dangerously suspect and handled only by individuals trained in the proper handling and disposal of explosive compounds.

The addition of alcohol or special chemicals (e.g., antioxidant BHT) help stabilize ethyl ether and inhibit peroxide formation.  To minimize any hazard associated with ethyl ether, it is best to purchase only small quantities that will be used immediately and not stored.  Recent experiments by wetplate photographers indicate that grain or denatured alcohol may be substituted for any additional ethyl ether called for in various collodion formulae.  Such substitutions eliminate the need to purchase and store ethyl ether and as a result, are strongly recommended for individuals practicing wetplate photography.

Note however that denatured alcohol is poisonous and not suitable for consumption.  Prolonged exposure to fumes of denatured alcohol should also be avoided for health reasons.  Because of the health concerns associated with use of denatured alcohols, the more expensive 190 proof ethanol is recommended as a substitute for ethyl ether in collodion formulas.  I do use denatured alcohols for cleaning labware, but I minimize my exposure to this chemical with good ventilation and I always wear chemical-resistant gloves when handling it.


Wetplate Collodion Formulas

Salted Collodion

Prepare the salted collodion by adding iodide and bromide salts, grain alcohol and ethyl ether to plain collodion.  (Note: flexible collodion will not work.  You must obtain and use Collodion USP in these formulations.)  Most salted collodion solutions need to ripen for several days before use.

For safety reasons, the substitution of 190 proof ethanol or denatured alcohol is sometimes recommended in these formulas in place of any additional ethyl ether.  Since ethyl ether is extremely volatile, highly flammable, and potentially explosive, collodion formulas should be mixed and stored away from ignition sources (open flame, hot plates, electrical fans, etc.).

In general, working collodion solutions contain approximately 1.5% bromide salt and slightly more than double that amount of an iodide salt. Common anions of these salts include potassium, ammonium, cadmium, lithium, zinc, or sodium ions.  Collodion formulas containing only potassium bromide and potassium iodide salts will clear quickly and be ready to use the same day, but their keeping properties are reduced.  On the other hand, cadmium collodions may take several days to ripen, but will age more slowly.  Ammonium salts also are used in quick-clearing formulas but they may produce irritating fumes and shorten the life of the working collodion as well.

Iodides add speed to collodion while bromide salts extend the spectral sensitivity and produce lower contrast results with a finer gradation in midtones .  As any collodion ages and turns from light straw to red in color, the contrast generally increases and the speed of the emulsion decreases.

Addition of either potassium bromide or potassium iodide in the formula will also cause any bromidized collodion to throw down a precipitate which may take several days to clear.

Potassium bromide and potassium Iodide are essentially insoluble in ethanol and so  must be dissolved in a minimum amount of distilled water before being added to collodion formulas.  Care must be taken to use the minimum amount of water because 190 proof ethanol already contains 5% water and collodions can only tolerate a certain percentage.  If too much water is present, the nitrocellulose (aka pyroxyline) will precipitate out of solution.  Warming the water will help dissolve iodide salts.


Carey Lea’s Landscape Collodion Formula #7

This is a double-cadmium salt collodion that has a long storage life and a slightly greater spectral sensitivity than some other formulas.  Because cadmium salts are used, the collodion tends to be more fragile and has a tendency to lift from the plate surface.  Subbing the plate edge with cotton swab saturated with albumen helps adhere this collodion film to the plate.  Note that cadmium salts are carcinogenic and should be handled using appropriate personal protection equipment.

Traditional Lea’s Landscape #7

Stock Alcoholic Bromo-Iodizing Solution:

In a clean bottle capable of holding at least 125ml (~4oz) mix:

190 Proof Grain Alcohol (Everclear or similar)

100 ml

Cadmium Bromide

1.5 g

Ammonium Bromide

1.3 g

Cadmium Iodide

3.4 g

Ammonium Iodide

2.6 g

First, dissolve the cadmium bromide in the alcohol.  Then, dissolve the ammonium bromide into that solution followed by the other two salts.

Working strength collodion formula:

In a clean bottle capable of holding at least 250ml (~8oz) mix:

Alcoholic Bromo-Iodizing Solution from above

40 ml

190 Proof Grain Alcohol

50 ml

Ethyl Ether

30 ml

Collodion USP solution (~6% pyroxilene collodion)

120 ml

Due to storage concerns and the difficulty obtaining diethyl ether, many wetplate photographers substitute either grain or denatured alcohols for any ether other than that inherent in the Collodion USP as purchased.  Such low-ether mixtures may contain more water than usual due to its presence in the grain alcohol.  The additional presence of water in the collodion may result in tender films, reduced adhesion to plates, and the need to extend the interval between pouring and sensitizing the plate.  As a result, you may find in your practice that the traditional amount of ether is a necessity.

There is some anecdotal evidence that the substitution of denatured alcohols for either grain alcohol or ether may rejuvenate salted collodions or prolong the working life of the mix.  However, be aware that denatured alcohols are manufactured to be intentionally toxic and any ingestion or prolonged exposure to the fumes of denatured alcohols is to be avoided.

Lea’s Landscape #7 Alternate Formula (eliminating additional ether)

Stock Alcoholic Bromo-Iodizing Solution:

In a clean bottle capable of holding at least 125ml (~4oz) mix:

190 Proof Grain Alcohol (Everclear or similar)

100 ml

Cadmium Bromide

1.5 g

Ammonium Bromide

1.3 g

Cadmium Iodide

3.4 g

Ammonium Iodide

2.6 g

First, dissolve the cadmium bromide in the alcohol.  Then, dissolve the ammonium bromide into that solution followed by the other two salts.

Working strength collodion formula:

In a clean bottle capable of holding at least 750ml (~24oz) mix:

Alcoholic Bromo-Iodizing Solution from above

100 ml

190 Proof Grain Alcohol

200 ml

Collodion USP solution (~6% pyroxilene collodion)

300 ml

The working collodion should be fully ripened
and ready to use within 2-3 days.

Quick-clearing collodion formulas may be found in several texts devoted to wetplate.  (Consult the bibliography.)

Quinn Jacobson's popular quick-clearing collodion formula is a modified version of a formula originally published in  M.H. Ellis' 1856 book, "The Ambrotype & Photographic Instructor." The following recipe makes 570ml of working collodion.  It  can be used almost immediately.

Quinn Jacobson’s Quick-clearing Collodion Formula

Part A:

Plain Collodion USP

240 ml

Diethyl Ether

160 ml

Part B:

Cadmium Bromide

3 g

Distilled Water

5 ml

Warming the water will facilitate the dissolution of the cadmium bromide.  A glass rod may be needed to break apart the cadmium salt which may cake in the water.  Many wetplaters mix Part B in a test tube and carefully employ an alcohol lamp or other heat source to gently warm the solution.

Part C:

Slowly mix Part B into Part A

Part D:

Ammonium Iodide

4 g

Distilled Water

5 ml

Grain Alcohol

160 ml

Slowly mix PART D into PART C and shake after each addition.


Silver Nitrate Sensitizing Bath

A sensitizing bath consisting of 9% silver nitrate with pH adjusted to make either negative or positive plate.  The actual volume of silver nitrate solution required depends upon the plate size being used and the capacity of the tank used for sensitizing the plates.  More neutral baths (pH ~ 6) work well for negative images while positives require an acidic bath (pH ~4-5).  Drops of nitric or glacial acetic acid may be used to adjust the pH.  Inexpensive pH monitoring paper or dedicated pH meters may be used to determine solution pH.

Once prepared, the specific gravity of the bath should be measured with a hydrometer and the initial value recorded.  A brewing or aquarium hydrometer is accurate enough for this measurement.  As the bath is used and the silver removed during sensitization of plates, additional silver nitrate should be added to replenish the bath and bring it to its initial value.

The silver bath should be slightly iodized by letting a coated salted collodion plate sit in it overnight before the initial use of the bath.

Note that silver nitrate is corrosive and may cause blindness if splashed into eyes.
Nitric and glacial acetic acids are also corrosive with caustic irritating fumes.
Use these chemicals only with proper personal protection equipment and adequate ventilation, and familiarize yourself with the MSDS information before attempting to use these chemicals.


Silver Nitrate Sensitizing Bath

Silver Nitrate

90 g

Distilled Water

1000 ml

Glacial Acetic Acid

as needed

Dissolve the silver nitrate in the water and carefully add drops of nitric or glacial acetic acid to bring the pH into the desired range for either collodion negatives (pH~6) or positives (pH~4-5).  Use extreme care when adding these acids to the silver nitrate solution.  These acids are extremely corrosive and inhaling their fumes may cause permanent pulmonary damage.  Finally, iodize the bath slightly by letting a collodion plate sit in the silver nitrate solution overnight.  This procedure saturates the bath with silver iodide and prevents the dissolution of that salt from the surface of subsequent plates where it forms during the sensitization process.

Check the initial specific gravity of the solution using a hydrometer.  Most inexpensive hydrometers used in brewing or aquarium applications will work .  You don’t need to purchase an expensive laboratory hydrometer.  Just be sure the hydrometer measurement range will incorporate values around 1 .07 which is a fairly standard measurement for the sensitizing bath.  Record the initial specific gravity level of the silver bath.  (I mark the hydrometer scale directly).  The bath may be replenished using a 30% silver nitrate solutions or by adding crystalline silver nitrate as needed.


Ferrous Sulfate Developer Formulas

Positive Developer for Ambrotypes, Aluminotypes, and Tintypes

Ferrous Sulfate

16 g

Distilled Water

400 ml

Glacial Acetic Acid

24 ml

190 Proof Grain Alcohol

16 ml

Filter the solution before use.

Development should be timed to about 15 seconds and ended before shadow details become present.  In hot conditions, the activity of the developer may be reduced and chemical fogging controlled by several means.  These include dilution of the developer with additional water, reduction in the amount of ferrous sulfate, increasing the acetic acid content, or use of an organic restrainer such as sugar in the formula.

Sugar Developer Variation

Ferrous Sulfate

15 g

Distilled Water

355 ml

White Table Sugar

20 g

Glacial Acetic Acid

20 ml

190 Proof Grain Alcohol

20 ml

Filter the solution before use.

For negatives, a weaker developer is used for an extended time, generally about 90 seconds.  Less ferrous sulfate and more acetic acid is used.

Negative Developer Formula

Ferrous Sulfate

9 g

Distilled Water

355 ml

Glacial Acetic Acid

28 ml

190 Proof Grain Alcohol

18 ml

Filter the solution before use.

In case of any unevenness of flow of the developer over the plate, a greater addition of alcohol will help the solution flow better.  (Some workers exploit this fact and use less developer to increase development streaks and other artifacts.)

Adding small amounts of potassium nitrate or silver nitrate will help brighten positive plates and produce a more neutral color.  A few drops of silver from the sensitizing bath will also help produce a brighter plate.  Many workers also save the used developer and mix it up to 50% with fresh developer to obtain similar results.

Filtering both fresh and used developers helps prevent small artifacts known as “comets” on the collodion plate.  A cotton ball or two placed in the neck of a funnel makes a filter sufficient for this purpose.  Silver nitrate solutions should also be filtered after daily use employing a dedicated funnel and fresh cotton to prevent contamination.


Fixer Formula

Fixer for Wetplate Photography

Sodium Thiosulfate

200 g

Cool water

1000 ml

Add the sodium thiosulfate crystals slowly to the water
and stir until dissolved completely.

Plates are fixed for twice the time they take to clear or fully reverse in the case of positive images.  Do not overfix plates.  Areas of collodion along the pour-off corner may be thicker and impervious to the fixing action, but otherwise the unexposed opaque bluish collodion film should clear before the plate is removed from the bath.


Glass Cleaner

Glass Cleaner

Whiting

50 g

Distilled Water

50 ml

190 Proof Grain Alcohol

10 ml

Mix the contents together in a clean condiment squeeze bottle by shaking.  The whiting will settle out so be sure to shake vigorously before use.  Apply a small puddle to the center of the glass plate and thoroughly clean the surface by rubbing with a soft cloth or paper towel.  (I prefer to use PEC Pads due to their durability when wet.)  Be sure to polish the cleaned plate with a lintless cloth and remove any powdered whiting that may remain on the plate including the edges.  Whiting is powdered calcium carbonate and the inadvertent introduction of this chemical into the silver sensitizing bath will raise the pH and cause problems.


Sandarac & Lavender Varnish

Sandarac & Lavender Varnish

190 Proof Grain Alcohol

470 ml

Gum Sandarac

65 g

Oil of Lavender

50 ml

In a lidded canning jar, dissolve the gum sandarac crystals in the alcohol by periodically shaking the bottle.  It may take several days to completely dissolve the sandarac.  Grinding the sandarac crystals to a smaller size using a mortar and pestle will speed the dissolution.  Filter to remove debris.  Add the oil of lavender to the filtered sandarac solution and mix until uniform.  Decant the varnish into smaller stoppered bottles.

To use, slightly warm the varnish bottle in a water bath while gently heating the back of the plate over a paraffin lamp.  Metal plates will warm rapidly while glass plates will take longer.  Don’t try to rush with glass because a sudden temperature shock may crack the glass.

Remove the plate from the proximity of the lamp and then flow the varnish smoothly over the plate as if making a collodion pour.  Let the plate rest horizontally for several seconds but not for too long since the  alcohol in the varnish may begin to dissolve the collodion film.  After several seconds, tip the plate vertically and from one corner, drain the excess back into a separate collection bottle.  Filter the varnish again before reuse.

Warm the back of the varnished plate over the lamp in order to evaporate the alcohol solvent and set the varnish.  Be careful to warm the plate slowly and avoid ignition of the alcohol coming off the surface.  The varnish will take several hours to dry completely so keep the plate away from dust during this time.

 Return to Previous Page of Wetplate Collodion Photography


Continue to Bibliography and Links for Wetplate Collodion Photography

 

Custom Search

 

[Home] [Articles] [Travel] [Books] [Links]

E-mail Webmaster