Collodion Tips & Technique Page Contents...

Plate Prep: Glass
Plate Prep: Tin
Pouring Collodion:
Sensitizing the Plate:
Making Your First Exposure:
Developing the Plate:
Varnishing the Plate:
Using a Light Meter:
Development Artifacts:

 Preparing Glass Plates:

Glass plates of various colors can be purchased from a variety of stained glass outlets. When purchasing glass, be sure to ask for "Float" glass. Unlike much of the glass used in stained glass applications, this type of glass has a smooth surface. For starters, and to keep things simple, you can purchase ordinary plate glass at your local hardware store to make your images. Once you have it cut to properly fit your plate holder, be sure to sand or "file" the edges. For this, one can use sandpaper or more conveniently a sharpening stone. Both serve the same purpose but the sharpening stone will last forever, is easier to handle, and is less messy. Keep the sharpening stone or sandpaper wet while filing the edges of the plate. This keeps the glass dust from blowing around in the air, getting on everything else, and being inhaled. Gently file all edges (both sides) of the glass plate to remove the sharpness. Be careful not to strike the plate with the sharpening stone as this might chip the glass or crack it. The purpose of filing the edges serves two purposes. First, it will make it less likely that you'll accidentally cut yourself later on, and secondly, it helps keep the collodion away from the very edge of the plate which helps prevent the collodion from catching and peeling.

When you've filed all the edges, wipe down the edges with a cloth or rinse with water to get rid of the excess glass dust from filing. Place the plate in a wooden vise, tighten the vise just enough to firmly hold the plate, and then pour a mixture of whiting (calcium carbonate, which is similar to chalk dust. This can be found in most stained glass supply stores) and alcohol. Use enough whiting to make a thin slurry that looks milky when poured onto a plate. Pour the whiting mixture onto the surface of the glass plate and then rub firmly and vigorously in small circular motions, covering the entire plate. Continue for a couple of minutes. Pay attention to the edge of the plate, they often get over looked and get less scrubbing time than the center of the plate. Wipe the surface dry with a clean dry flannel. Flip the plate over and repeat on the opposite side. When done, remove the plate from the vise and wipe down the edges of the glass to remove any excess whiting that may have collected there (this keeps the chalk dust from contaminating your silver nitrate bath later on).

Before moving on to the next step (which is coating the plate), make sure your camera is set up, your shot composed, and your exposure calculated. Once the collodion is poured on the plate, you have a limited amount of time with which to work before the collodion dries out and is no longer usable. The practical working time depends on the temperature and humidity of the day. Generally, 75 F degrees and 40% humidity will give you approximately 10 or 15 minutes of working time. Experience will tell you how long you have to work under the conditions in your area.

^ back to top ^

 Preparing Tin Plates:

Tin can come in a couple of different flavors: precoated, or japaned. The word "Tin" is a a colloqualism of sorts in the world of collodion photography that refers to the metal substrate that supports the collodion film which forms the image. The actual metal is not tin, anymore than the metal making "tin" cans is made of tin. It's really just an expression. Quite often the material is steel which has been coated with bitumin and/or asphaultum to give it a glossy black finish, or it may be a sheet of aluminum that has been prefabricated with a glossy black finish and covered with a protective plastic sheet. This discussion will focus on the prefabricated aluminum sheets.

The prefabricated sheets are by far the easiest route to go. These sheets are covered with a protective layer of static cling plastic, not unlike plastic wrap found in your kitchen drawer. Be sure to remove this protective layer just before pouring your collodion. In many cases this is all you need to do. However, don't let this ease of use allow your trouble shooting skills to become soft. Collodion photography is as much about science and trouble shooting as it is art and photography (and maybe more so!). When using precoated "tin" you may occasionally encounter artifacts caused by contaminants getting on the surface of the plate during its manufacture. These artifacts will show up as a "regular" pattern of streaks or spots aligned along one axis of the plate when the image is developed. This regular appearance is quite different than most other artifacts encountered in the collodion process which tend to have an amorphous shape or no pattern at all.

Always keep in mind, like most materials used in collodion photography, the originally intended use of precoated tin is for industrial and/or mechanical applications, not photography - so the manufacturers aren't on the lookout out for the occasional drip of lubricant that finds its way onto the coated surface of the huge sheets as they make their way through the machinery and rollers that repetitively print out that one drip of contaminant like an ink roller leaving an imprint on paper until the ink finally runs out (this is the reason the artifacts you may see are generally aligned along one axis of the plate)

But having said this, not all is lost! Even though there's a potential risk of running into contamination from the manufacturing processes, this is greatly outweighed by precoated tin's convenience (as compared to japaning your own plates, which can be done, though it's a little messy and time consuming). The solution, should you encounter this, is to simply wipe the plate down with alcohol and/or ether prior to coating it with collodion. This should remove whatever surface contaminants are on the plate which might cause spotting or streaking. If you find you still have artifacts, you may try cleaning the surface a little more aggressively by abrading it with a mixture of calcium carbonate(chalk dust) and alcohol, just as you would with glass preparation.

Another thing to keep in mind, is that even if you've made an image on tin and you don't like it for whatever reason, it's an easy matter to wipe the plate down with alcohol and a cloth or paper towel to remove the collodion/image and return the plate to it's original black surface and coat the plate again for another image.

^ back to top ^

 Pouring Collodion:

Handle your collodion as if it were nitroglycerine. Don't shake it, and pour it gently and slowly. Never worry about getting the last drops out of the bottom of the bottle. Collodion is constantly throwing down chemistry as it ages and this all settles out on the bottom. Using the dredges will result in pinholes throughout your image. Now that the warnings are out of the way...

To coat the plate, hold it at one corner using your index and middle fingers to support it from below, while your thumb holds the very corner of the glass from the top side.

Hold the plate precisely level. Pour the collodion slowly but steadily onto the center of the plate. As you pour the collodion, it will form a circular pool in the middle of the plate. Adjust the tilt of the plate as necessary to maintain the circular shape until enough collodion has been poured to amply cover the plate. Remember, work slowly and methodically. You have more time to coat the plate than what you think, so take your time. You will also need to pour more collodion onto the plate than you think you'll need, so be generous. Remember, you can always drain off any excess after the plate is coated.

When flowing the collodion over the plate, plan ahead. It doesn't matter whether you move it in a clockwise or counterclockwise direction, or from which corner you pour back into the bottle. As long as you work in a consistent fashion, you'll be okay. For the sake of illustration, let's assume we are holding the plate with the left hand. We'll begin by flowing the collodion into the near left corner, then move clockwise from there to the far left, then the far right, finally pouring off into the collodion bottle at the near right corner. When I mention tipping the plate, don't physically tip the plate as much as "Think" about tipping the glass. It doesn't take much!

Here we go: Once enough collodion has been poured onto the plate, gently tip the glass toward the left and a little bit toward you. The collodion will gradually begin to flow to the near left corner.

As it approaches the edge of the glass gently tip the plate away from you until the collodion approaches the far left corner.

Then gently tip the glass to right so the collodion moves into the far right corner.

And finally tip the plate toward you slightly to drain the excess collodion off the corner of the plate and back into your collodion bottle. Don't hurry the collodion or try to force it back into the bottle. This will usually result in spills off the edge of the plate. Just keep everything flowing at a constant rate and you'll be a pro in no time.

Some general precautions when flowing the plate: Always keep the collodion moving outward from the center pour. Don't try to tip the plate backwards to "coat a spot you might have missed". This will inevitably leave a thick ridge as it builds up on the collodion that has already dried to some extent. Once you begin draining the collodion back into the bottle, begin rocking the plate from side to side to prevent ripples from forming on the surface of the collodion. (These ripples will show up in your image later if you don't take care of them now!)

When the collodion stops draining from the plate, raise the plate and cap the bottle. Continue rocking the plate slowly from landscape orientation to portrait orientation (about 1 or 2 seconds per rotation) while always keeping the draining point at the bottom. Continue rocking until the collodion becomes firm, but not dry. You can tell when it's ready by gently touching the collodion at the draining corner, when your finger leaves a dent without feeling wet or slipery, it's ready.

^ back to top ^

Hold the plate level.
Pour collodion onto the center of the plate.
Tip the plate slightly forward and left
Tip the plate slightly away.
Then to the right
And finally forward again
Pour off excess collodion.
Rotate the plate.
 Sensitizing the Plate:

Dip the newly coated plate into the silver nitrate bath. Do this with confidence, lowering it smoothly and evenly into the tank. This should only take 2 or 3 seconds to accomplish. Don't splash or disturb the solution any more than absolutely necessary and don't hesitate while inserting the plate into the liquid. Hesitation can cause lines in the image later on. Once the plate is in the silver nitrate, close the lid of the tank and wait approximately 2 minutes.

While the plate is in the sensitizer, this is a good time to prepare your materials for development. Set out a tray large enough for your plate, a beaker or wide mouth jar of distilled water to stop the development, and a small beaker (50ml) or shot glass to hold the developer. Pour out a sufficient amount of developer to cover the glass plate (for example a 7x9 inch plate would require about 10 ml of developer).

After approximately 2 minutes, pull the plate from the liquid in the same confident manner in which it was inserted. Again, avoid hesitation. Look at the surface of the plate as you're pulling it out. If you see an oily appearance with rivulets running off, the plate needs to be reinserted into the silver nitrate. If the silver nitrate flows smoothly off the surface when it's removed from the tank, it's ready for the plate holder.

Blot the excess silver nitrate from the edges of the plate by placing a clean dry paper towel on the darkroom bench, and setting the edge of the plate on the towel. Rock the plate forward and back slightly, then repeat the procedure on the other edges as necessary. Insert the plate in the holder with the collodion side toward the dark slide (usually down). Gently wipe the back of the plate with a dry towel to remove any excess silver. Close the plate holder.

^ back to top ^

 Making Your First Exposure:

A simple test exposure can be made by using the dark slide of the plate holder. Start out by exposing the entire plate for a base amount of time (this depends upon the lighting conditions and the f/stop used). After the base exposure, push the dark slide 1/4 of the way closed and expose again for one base exposure. Push the dark slide in ½ of the way closed and expose again for two base exposures. Finally slide the dark slide in 3/4 of the way and expose again for four base exposures. This will give you total exposures on the collodion of 1x, 2x, 4x, and 8x the base exposure. In other words, 4 exposures separated by one-stop intervals.

Develop and fix the plate as you would normally and inspect the image for the appropriate exposure range. This is a great technique if you're just starting out, using a camera you're unfamiliar with, trying out a new lens, or working in unfamiliar lighting conditions.

^ back to top ^

Dark slide full open.
Expose Plate 1X Base Exposure
(Total exposure on plate = 1x Base)
Push dark slide 1/4 way in.
Expose Plate 1X Base Exposure
(Total exposure on plate = 2x Base or +1 stop)
Push dark slide 1/2 way in.
Expose Plate 2X Base Exposure
(Total exposure on plate = 4x Base or +2 stop)
Push dark slide 3/4 way in.
Expose Plate 4X Base Exposure
(Total exposure on plate = 8x Base or +3 stop)
 Developing the Plate:

Development can be done in a tray or by applying the developer directly to the hand held plate. Development of collodion requires free sliver nitrate to be on the surface of the plate, thus it is important to flow the developer evenly over the surface of the plate from one side without causing turbulence that would wash the silver off the plate. Pouring directly onto the plate surface from above will prevent full development where the developer first impacts the plate, producing thin images at that location. Properly flowing developer onto a hand held plate takes a little practice, but is worth the effort because it allows you to observe the progress of development and to stop the development without delay.

Bring the newly exposed plate into the darkroom and remove the plate from the holder. Hold the plate with the collodion side up, in one hand above an oversized tray (the tray is there to catch the spills). Position yourself so that you can see a glare from the safe light on the surface of the glass. This will help you determine how the developer flows onto the plate. In the other hand hold the small beaker of developer over the edge of the plate near the far corner. Tip the plate away from the beaker so that the developer will run down the plate in a wave toward the hand holding the plate. Pour the developer by drawing the beaker long the side of the plate, continually pouring along the length. Tip the plate as necessary to keep the developer flowing evenly across the plate. Watch for areas that the developer might miss (dry spots) and move the plate quickly as necessary to try and force the developer to cover these areas. Continue moving the plate, agitating the liquid on the surface until the image begins to form. When the image is properly formed (mid tones formed with shadow areas remaining clear) pour distilled water onto the plate to wash off the developer and excess silver. When the plate is thoroughly washed, the water will sheet smoothly off the surface. If the plate looks oily, continue washing. Once the developer and excess silver nitrate are washed from the surface, the plate can be viewed in daylight. At this point, the plate is ready for fixing.

Fix the plate in hypo (sodium thiosulphate) for 3 to 5 minutes or until the plate has cleared. This can be done in either a tray or tank.

Wash in running water for 20 minutes to remove all traces of fixer.

^ back to top ^

Flowing the developer onto the plate.
 Varnishing/Finishing the Plate:

The traditional method of finishing a plate is to varnish it after it's thoroughly dry. This is done by carefully pouring a sandarac varnish over the warmed plate and drying it over a lamp or heater. It's fairly delicate work and provides all sorts of opportunities to ruin a great plate. With this in mind, always always always (did I say always?) scan your plate before you varnish it. That way you at least have a digital back up. In spite of the potential difficulties in learning the techniques of varnishing plates, it is a proven technique for sealing and preserving collodion images. It's worth the effort to master these skills.

Now, getting back to varnishing...First, pour a small amount of varnish into a pouring bottle and warm it in a beaker of water. Warm your plate over a hot plate, alcohol burner, or kerosene lamp (not hot! if you can't touch it to the underside of your wrist, it's too hot) Keep the plate moving so it heats evenly. Pour the varnish as you would pour collodion, beginning with a circular pool of varnish in the middle of your plate, then tipping the plate to the left, then away, then to the right, then finally toward you and draining the excess back into a second bottle which you will then filter again before reuse. Blot the edges of the plate on a clean paper towel, while rocking the plate toward and away from you to remove any excess buildup of varnish from the edges of the plate. Heat the plate again over an alcohol burner until the varnish has set. Place the plate in a drying rack and allow it to cure for at least 24 hours.

Now, if you're not that concerned with traditional methods, and you're feeling a little experimental, you may want to try spray polyurathane. I should offer a disclaimer here: these materials have not been tested over time, and may, or may not, cause harm to the image in years to come. There have been anecdotal reports of peeling or flaking of the collodion many years after it's been coated with paint, but I'm unaware of the details regarding the materials used in these cases. There are some differences between brands of polyurathane and the best I've seen to date is Minwax Premium Spray Polyurathane. This seems to level uniformly, provide the smoothest coat, and produce a beautifully glossy finish. As with traditional varnishing, you need to warm your plate to drive off any moisture that may be in the collodion. If you don't do this, you will see cloudy white areas show up in your image. Apply 3 or four very light coats crossing the plate in various directions. The idea here is not to leave a spray pattern in the finish.

If you're shooting clear glass ambrotypes, you have yet another method available. Black spray paint. Eeeekkkk!! Black? Yes, black. The beauty of this is, you'll be viewing your image from the glass side of the image which provides a pristine perfectly smooth and glossy surface to the front side of the image while the black paint now does double duty by sealing and protecting the collodion while it forms the black backing that you would normally mount behind the image. The advantages here are several: you no longer have to worry about the slightest bit of dust showing up in your finish, keeping a glossy texture is not important at all, and you've eliminated the air gap between the image and the black surface, thereby eliminating reflections between the glass and the background which gives you a much deeper black in the shadow areas of your image...yummmm!!! It really makes the image pop. Secondarily, you may even want to experiment with different colors of paint! If you do this, remember to stay on the dark side, since lighter tones will make your image appear as a negative. But this could be interesting too, depending on what you're looking for.

^ back to top ^

Varnishing the plate.
 Using a Light Meter with Collodion:

The first thing to note about collodion is that it is sensitive well into the ultra violet region of the spectrum, a region neither our eyes nor our light meters will detect. It is not sensitive to colors with wavelengths longer than green (red, orange, and yellow). However, for metering purposes, we can make the simple and reasonable assumption that the UV intensity tracks uniformly with visible light intensity. This means that when the scene you're about to photograph gets brighter in the visible portion of the spectrum, it gets equally brighter in the UV portion of the spectrum.

Once a good exposure is obtained on collodion, meter the scene and record the Exposure Index (EI) or Exposure Value (EV) that's indicated on the meter. Metering after an exposure is quite the opposite of what you may expect, however, there is method to this madness! Even though the meter didn't help us with the first exposure (that's why we needed the test strip), it will help us with each subsequent exposure. Don't worry about ASA or f-stops at this point; all we're looking for are relative differences in light intensity as we move to our next scene.

When we set up the next shot under different lighting conditions, meter the scene first and record the EI. The difference between the original exposure index and the new exposure index is the number of stops difference in light intensity between the two scenes, and this is what you will use to determine your new exposure setting (f-stop and exposure time). Remember, a change of one unit on the EI scale is equivalent to a change of one f-stop, or a doubling (or halving) of the exposure time. So, if the scene brightness changed by 3 units of EI, then you know that you need to change the f-stop on your camera by 3 stops, or you need to change the exposure time by an equivalent of 3 stops (or use some combination of both). This method of metering will often save a great deal of guess work and bring you very close to the proper exposure on the first try.

Mastering the techniques of pouring collodion, developer, and metering take a little time and practice, but it is time well spent.

^ back to top ^

 Trouble Shooting:

Collodion Peeling or Lifting from the Plate:

The "usual suspect" for collodion that peels or lifts from the plate is a plate that has been inadequately cleaned. Wear nitrile gloves when handling the plates to avoid getting finger prints and oils on the glass while handling it. Scour the plate with a slightly abrasive cleanser like Bonami, and rinse thoroughly under running water until the water sheets off smoothly without forming little rivulets on the surface of the glass. Place the plate in a rack to dry. Prior to pouring the plate, use a mixture of alcohol and whiting (powdered calcium carbonate) to scrub the plate. Finish cleaning the plate by buffing it vigorously with a clean flannel cloth. Wipe all edges to remove any whiting that may have collected there while cleaning. Pour the freshly cleaned plate and process it. If you still find the collodion is peeling or lifting from the plate, try increasing the amount of alcohol in the collodion mixture as described below.

Our second suspect is alcohol content. Generally, collodion (5% USP, as obtained commercially) is thinned for use in photography with equal parts of ether and alcohol. If the relative amounts of each solvent (ether and alcohol) are varied along a continuum from primarily ether (and very little alcohol) to primarily alcohol (and very little ether), one will find the collodion film to vary in physical character from tough and leathery to spongy and fragile. If too much ether is used, not only with the film be tough, but it will also be prone to shrinking on the order of 2.5% when it dries. This may not sound like much, but on a 10 inch plate, this is equivalent to 1/4 inch. It's this combination of shrinkage and leathery nature of the film that's responsible for the film peeling and sliding off the plate. To prevent this, it is necessary to increase the percentage of alcohol in the mixture. Begin by adding a volume of alcohol equivalent to 5% of the total collodion volume being used. Swirl the alcohol into the collodion mixture then pour and process a new plate. If peeling still occurs, add an additional 5% alcohol to the collodion and repeat. As more alcohol is added to the collodion, the film begins to lose its tough, leathery, character and becomes spongey and fragile.

When all else can apply albumen to your plate prior to coating the plate with collodion. This process isn't particularly complicated, it just takes a little time and preparation. First, to get the albumen, you have three options: separate the white from an egg, buy a carton of egg whites from the grocery store, or purchase powdered egg white and add water. Separating the white from an egg is probably the the quickest solution since eggs are relatively close at hand for most folks. The quick and dirty solution is to dip a cotton swab into the albumen and paint the perimeter of the plate, making a border about 1/4 inch wide. Let this dry completely before coating the plate with collodion. This will keep your collodion from peeling, but it will leave a darker boarder around your print where the albumen was applied. A slightly more involved procedure is to mix the egg white with water in a ratio of about 1/40. This is approximately one egg white in 1 liter of water. Mix this thoroughly and filter before use. Pour this solution onto the plate as you would pour collodion. Avoid creating bubbles or trapping dust on the plate. Allow the plate to dry thoroughly before applying the collodion. This method avoids the dark border and insures that the collodion will stick to the glass.

^ back to top ^


Comets are streaks that show up on the plate that originate at a point or grain of contamination in or on the collodion film. As the plate is dipped into the silver nitrate, this contamination is drawn away from the original point by the relative motion between the silver nitrate solution and the plate, forming the comet's swept tail. I'm still investigating the various causes, but at present it appears the contamination that causes comets can be either chemical, or physical, and appear to originate with the collodion and not with the silver bath. To minimize the possibility of forming comets, be sure to handle the collodion gently. Avoid mixing or shaking the collodion prior to use. Allow any particulate matter to settle out of the solution before using.

This is a magnified view of a comet that appears to be a physical obstruction imbedded in the collodion film. Notice the bumps sticking up above the collodion surface. This is a magnified view of a different comet that appears to be chemical in nature and one that is located within the collodion film and not distorting the surface of the film as seen in the first image. Notice the central "grain" that's resides in a very well defined region completely devoid of developed silver.

This is a magnified stereo image of a comet protruding above the collodion's surface, taken in reflected light.

This is a magnified stereo image of a comet caused by a chemical grain within the collodion film, illuminated by transmitted light.

This is the same comet as shown above, illuminated by reflected light.

^ back to top ^

Pouring Developer Directly onto One Spot:

Development is both a physical and chemical process. The chemical part of the process involves reducing the exposed silver iodide in the collodion film into metallic silver through the action of the developing agents. The physical aspect of the development comes into play because the presence of free silver nitrate is necessary for the chemical action to occur. An aqueous solution of free silver nitrate normally coats the surface of the plate after sensitizing it. This is the "Wet" in wet-plate. Because it's a liquid, it can easily be moved around on the plate.

The reason we use as little developer as possible during development is to keep the concentration of the free silver nitrate high enough to do it's job, and bring out an image. If, the free silver nitrate is washed away by physically "splashing" the developer onto the plate, the image won't form properly.

The most obvious way of pushing this free silver nitrate away is by pouring the developer directly onto the plate in one spot, causing the stream of developer to strike the plate with some force. This effectively pushes the free silver nitrate away from this spot, producing a somewhat circular region that has little or no image.

This image was produced by pouring the developer directly onto one spot on the plate. Artifacts like this are typically between 1/2 and 1 inch in diameter.

This is the same artifact, but the speed of the pour was much greater. Notice the extra bands surrounding the central portion. These were caused by waves and ripples as the developer "splashed" away from the center. This artifact is about 2 inches in diameter.

Errors like this, can be corrected by allowing the developer to flow as smoothly and evenly as possible across the plate.

^ back to top ^