Wet Plate Collodion Process


Click Here for photos of my wet plates.



While looking at photographic processes in general, I came across Wet Plate Collodion. This process was invented in the year 1850 and was the second most popular process. Its predecessor was the Daguerreotype and successor was the invention of the gelatin dry plate. I was drawn to wet plate because of its uniqueness and the actual process on how to produce a plate. With this process a tintype, ambrotype or negative could be produced. The Tintype is a positive image made on blackened/japanned tin or aluminum plate. An Ambrotype is also a positive image made on a piece of black or clear glass. This glass is already black or is blackened or is backed by something black. Like the tintype, the black background gives the illusion of a positive... the image is actually an underexposed negative. This means that the plate is a direct positive and has no corresponding negative. Therefore, they are not easily reproduced. Lastly, a negative is on a clear piece of glass but with a denser image (which should looked overexposed/bright if backed with black background). A negative is normally exposed for twice the amount of time of an tin/ambrotype and is developed with a separate developer. The negative could be enlarged, contact printed or scanned but a tin/ambrotype cannot be made from it. After the plate is sensitized in the silver bath, it is only sensitive to blue and UV light. Therefore, they must be shot outside in sunlight or shade or have multiple flourescent lights setup.

The main drawback of wet plate is that the plate must remain wet until fully washed. Between when it is taken out of the silver bath (step 3) to being developed (step 6), the plate will remain wet for 10 minutes or less depending on the ambient temperature. Therefore, an on-site darkroom is necessary.

While writing this article, I originally wasn't intending for it to be a how-to but ended up being that way... so bare with me if it isn't fully complete/thorough. I didn't purchase any manuals like so many forum members suggest, I just did lots of research. It's not rocket science, you too could learn wet plate collodion with or without a manual! All of the information you need is freely published online including the formulas! Honestly, I found wet plate to be easier than designing and building the 4in Tesla Coil (there are no manuals on tesla coils)! I hope my experiences help another fellow wet plater succeed! Any new wet platers should register on the Collodion forum! It's a great place to learn about wet plate and to diagnose and troubleshoot problems.


Click Here for photos of my wet plates.

Wet Plate Collodion Process in a Nutshell:

1. Pour Collodion onto a tin or glass plate. Cover the whole plate and drain excess into a separate bottle. Pour in a large room or outside as it's quite aromatic!
2. After Collodion has set, place into the silver bath for 3 minutes.
3. Remove plate from silver bath and dry the back of the plate but do not dry the collodion side. Do this under safelighting (usually red). The plate is now light sensitive.
4. Place the plate into the modified wet plate film holder.
5. Place the wet plate film holder into the pre-setup large format camera and expose.
6. Return to the darkroom and develop the plate. 15 seconds for a positive and 60 seconds for a negative.
7. Pour water onto the plate to wash off the developer as quickly as possible to stop the developing action.
8. Fix the plate for 1-2 minutes in Rapid Fixer. The plate is not sensitive to light anymore.
9. Rinse the plate in water and place into hypo clear bath for 2 minutes.
10. Wash for at least 5 minutes in running water.
11. Place plate onto drying rack to dry.
12. Buff the plate with a cotton ball before varnishing (optional).
13. Warm the varnish bottle in a cup of hot tap water.
14. Heat the underside of the plate evenly (image facing up) with an alcohol lamp until almost too hot to handle.
15. Flow the plate with warm varnish like you would with collodion. Cover the whole plate and drain excess into a separate bottle.
16. Let sit for at least a minute or two so that the alcohol evaporates.
17. Reheat the plate until the varnish starts to smoke. The varnish is now set and smells great!
18. Let completely set overnight.
19. Sign and date the back and admire the fruits of your labor!



Above: The very first plate I made (was just mainly overexposed)! Here's the correctly exposed one.


How wet plate collodion works (technical description):

The silver nitrate reacts with the bromide and iodide compounds in the collodion to form silver bromide (AgBr) and silver iodide (AgI), which is still held by the nitrocellulose on the plate. The silver halides are now mostly white/bluish in color and are light sensitive. After the plate is exposed, there is an invisible latent image. The plate is developed using Iron (II) Sulfate, which reduces the exposed AgBr and AgI to the non-light sensitive Silver (II) Sulfate. Since the unexposed/undeveloped silver (silver halides) are still light sensitive, it is fixed to remove them from the plate. While being fixed, the white silver halides disappear, leaving a positive/negative image. The fixed plate is then placed into a bath of Sodium Sulfite (hypo clear) to help remove the excess fixer. The plate is washed for 5 minutes to remove all traces of fixer and dried. Finally, it is varnished to protect the silver from damage and oxidization.




The Collodion is actually the film base that holds the image to the plate. It is usually comprised of Nitrocellulose (gun/nitrated cotton), Ether, 95% Grain Alcohol (everclear) and usually two or more Iodide and Bromide compounds. The typical salts are a combination of Ammonium, Potassium or Cadmium Iodide and Bromide. Note that the Collodion is not light sensitive at this point. There are many different formulas but mainly only differ in shelf-life, clearing and seasoning time. Some formulas will be cloudy and take from a few days to few weeks to clear. Also, the seasoning time (when contrast is best) could take a few weeks to few months. Here are two different formulas that I have used:


Old Workhorse Collodion Formula

Part A:

Cadmium Bromide - 0.8g

Ammonium Bromide - 0.7g

Distilled Water - 3mL

Fully dissolve both metal salts then add and dissolve:

Potassium Iodide - 2.5g

Then add mixture to:

95% Grain Alcohol - 100mL

This concludes Part A.


Part B:

Ether - 50mL

Plain Collodion USP - 120mL

Add Part A to Part B and shake bottle to ensure a homogeneous mixture. After this initial shake, do not shake again since there will be a precipitate that will settle to the bottom of the bottle. The shelf life of this formula is said to be about 1 year. The salted collodion is ready to use after about 1-2 weeks of ripening time.



Quinn's Quick Clear Collodion Formula

Part A:
Cadmium Bromide - 3g
Dissolve the CdBr into 5mL Distilled Water and add to:
Ammonium Iodide - 4g
95% Grain Alcohol - 160mL

Part B:
Collodion USP (non flexible) - 240mL
Diethyl Ether - 160mL

To use, mix 3 parts of A + 7 parts of B. In my experience, the solution clears immediately and should be ready to use but I usually wait a few hours. The Collodion should be a light straw yellow color. With use and age, it will become dark yellow to orange to dark red. This formula is reported to have its optimal contrast when about two weeks old and has a life span of about 2-3 months (but could be extended... read below).

Cautionary Note:

Collodion, Ether and Grain Alcohol are extremely flammable. Never store Collodion or Ether by an ignition source or in a refrigerator. This is because the ether fumes will collect in a small space and could be ignited by the compressor or other source inside the fridge. Pour plates in a large open space or outside so fumes don't collect. Also don't pour plates in a darkroom since the acid fumes from the developer will accelerate the aging of the collodion. Store collodion and ether in a air tight container. I keep mine in a tupperware container with an o-ring'd lid from Target. Even then, you can still smell the ether... it is powerful stuff and VERY volatile. Handle all Cadmium compounds with caution since they are known carcinogens and accumulates in the body. If collodion is spilled onto the skin (which will happen), use isopropyl alcohol to remove.


Pouring a Plate:

First dust off the plate with a dedicated brush. Then the Collodion is poured onto the top of the plate, which is held "waiter style" and is tilted to each corner to cover the whole plate. The excess Collodion is then drained from one corner into a separate bottle and is saved. Let the pour-off corner rest onto a piece of paper towel so that the excess could wick off of the plate. This poured plate is placed into the silver bath for 3 min after it sets (which is usually almost immeadiately wicking stops). This video from Quinn gives a good demonstration on how to pour a plate.

Extending the lifespan of the Collodion:

Fortunately, there is a way to increase the life span of Collodion and I have tested it with great results! It's very simple, when the Collodion gets red, add 0.5mL Acetone (I used Kleen Strip brand) to 75mL of Collodion. With my dropper/pipette, 10 drops = ~0.5mL. My Quick Clear collodion was 3 months old at the time. Over the next few days to weeks, the Collodion will slowly but surely change from red back to mid yellow! My tests have shown that the contrast will change back to around optimal within a week or two. Theoretically, you could add the acetone to new collodion and it won't age nearly as fast but I have not tested that yet. Note: don't be tempted to add more acetone so that it reverses faster... you might have a problem with the image melting when varnishing! I cannot confirm this myself but a forum member had this problem after he added 2mL Acetone to 100mL Collodion. Using my ratio of 0.5mL to 75mL has not caused any image melting problems. Also, I have noticed that the collodion is less fragile when wiping with a cotton ball while still wet. Comparisons are below. Also click here and here for more plates made with collodion with acetone.


Left: 3 month old Collodion. Right: 3 month old Quick Clear Collodion with acetone added ("reversing" for 3 weeks).


Left: 3 months old collodion without acetone. Right: Collodion with acetone added ("reversing" for 7 days).

Note: the exposure time and development is the same and taken within 10 minutes of each other.



Above: Quick Clear Collodion 1 day old.

Above: Quick Clear Collodion 6 weeks old.

Above: 3 month old Quick Clear Collodion with acetone added ("reversing" for 7 days).



The silver bath is use to sensitize a freshly poured plate. It is composed of a 9% Silver Nitrate solution. After sensitization, the plate will be sensitive to mainly blue, UV light and some green light. Colors like red or orange will appear pitch black. Wear nitrile gloves when handling silver nitrate, it will stain your skin dark brown and will not wash out easily! When using the bath for normal use, slowly but steadily lower the plate into the tank to prevent lines or streaks.

9% Silver Bath Formula:

Silver Nitrate - 90g
Distilled Water - 1000mL
Glacial Acetic Acid or Nitric Acid - add until pH ~4

Cautionary Note:

Silver Nitrate, Glacial Acetic Acid (99% vinegar) and Nitric Acid are very corrosive and could cause severe burns or blindness if splashed into your eyes! Do not inhale the Glacial Acetic Acid fumes as they too are corrosive... you WILL know when the bottle is opened! Nitric Acid is an oxidizer... Keep Nitric Acid away from bases and organics as the reaction is quite violent and could release toxic, corrosive Nitrogen Dioxide gas (mixing with copper will do this).


The 9% silver nitrate solution should be placed into a purpose built tank, which is usually a light tight tank made of black or dark red plexiglass. The tank should have a lid to keep dust & light out and a dipper to easily insert and remove the plate. Note that the silver bath itself is not really light sensitive but the plate will be!

After making a new bath, use a Hydrometer to measure the specific gravity. It should read around 1.075 but could be different for other hydrometers so be sure check yourself. Then pour a plate with collodion and let it sit in the bath overnight to iodize/season it. This is to saturate the bath with silver iodides so that subsequent plates will retain its silver iodides. It is now ready for action!


Above: Handmade quarter plate (3.25x4.25in) silver tank with dipper (below).


Above: 8x10 Silver Tank (purchased online)

Maintaining the Silver Bath:

The silver bath will require maintenance if contaminated or after a number of plates. Check the specific gravity, if below 1.040, add silver until it reaches the SG for a new bath. Contamination of the bath could be caused by a number of things such as dirty plates, bad collodion, dust, dirty silver tank, over iodization, tap water, too much ether/alcohol gathered from many plates or from accidentally mixing in other foreign chemicals. Usually, a contaminated bath will be cloudy and/or causing image problems such as fogging, spots, a white coating (that can be wiped off) and a few others that I have not experienced yet.

Fortunately, it is possible to fully rejuvenate a contaminated/overused bath... of course to a certain extent. The simplest and easiest is to sun the bath. Pour the silver solution into a clear bottle and place in the sun for a few hours, I usually let it sun for a whole day. Any contaminants will "develop" out of the solution as black precipitate and will sink to the bottom. Filter the solution through a few coffee filters stacked together. The sunned and filtered solution should be clear and ready to use.

For heavy maintenance such as removing the iodides from an over iodized bath you need to: Neutralize it to pH 7 with Ammonium Hydroxide (Ammonia). Add about 1/3 of the total volume with distilled water to force the iodides to precipitate out of solution (it should be cloudy). Filter if necessary. Sun for several hours. Filter. Now boil until original volume is obtained. Filter if necessary. Sun again for several hours. Filter. Finally, re-acidify until pH ~4. Check the SG and add silver if necessary. Re-check the pH and add acid if necessary. Also completely wash the silver tank and rinse with distilled water several times before pouring in the rejuvenated silver solution. Because the iodides have been removed, treat it as a brand new bath and re-iodize it again before use.

Overall, I think that it's pretty amazing that the silver bath could be rejuvenated and the collodion could be reversed considering that it's not possible with most darkroom chemicals. But then again, normal darkroom chemicals are cheap and easy to replace. Luckily, the expensive chemicals can be reconstituted in this case.




There are two developers used in wet plate: one for positives (tin/ambrotypes) and one for negatives. Here are the formulas I use:

Developer for positives:

Ferrous (Iron) Sulfate - 16g
Distilled Water - 400mL
Glacial Acetic Acid - 24mL
95% Grain Alcohol - 16mL

Developer for negatives:

Ferrous (Iron) Sulfate - 9g
Distilled Water - 355mL
Glacial Acetic Acid - 28mL
95% Grain Alcohol - 18mL

For positives, I develop for 15 seconds and no more to prevent fogging. For negatives, I develop for 60 seconds at twice the exposure time for a positive. The negative developer is basically a weaker version of the positive developer, so that development could be longer, which brings out more halftones. These are to be used as one shot developers.

To develop, flood the plate very quickly with developer (<1 second). The best way i've found to achieve that is to position your bottle of developer at the top of the plate (while holding waiter style) and steadily start pouring while moving the bottle down the side of the plate. Once covered, keep as much developer as possible on the plate and slightly agitate. Once the development time is up, pour water on the plate to stop the development as quickly as possible. The developer is washed off when the greasy/oily look disappears when you stop pouring water. In my experience, fogging will develop if the developer is above 75-80F (I live in Phoenix so that is certainly possible). So, keep the bottle of developer in an ice bath and all will be good. Here's another link by Quinn that gives a good demonstration on flowing the plate quickly.




For fixing I use Ilford Rapid Fix 1+4 ratio. This is an Ammonium Thiosulfate based version and fixes in less than a minute. There are three possible fixers that could be used, Sodium Thiosulfate, Ammonium Thiosulfate and the ever so dangerous Potassium Cyanide. And yes, it is the same cyanide that is used in suicide pills. I chose not to use Potassium Cyanide for safety reasons and use Rapid Fixer for its rapid fixing action and fast wash times.

Simple Hypo Fixer:

20% solution of Sodium Thiosulfate

After fixing, the plate is then placed into a bath of Sodium Sulfite (hypo clear) to help remove the excess fixer. The plate is washed for at least 5 minutes under running water to remove all traces of fixer and dried.




Varnishing the plate is necessary to protect the image from damage and oxidation (the silver will tarnish over time). The traditional varnish is comprised of Gum Sandarac tree resin, Lavender oil and 95% Grain Alcohol (Everclear). To varnish a plate, use an alcohol lamp and heat evenly until almost too hot to handle. Then pour warm varnish and flow like you would when pouring a plate with Collodion. In my experience, the varnish has to be warm (100F) otherwise there will be islands where varnish didn't want to flow. Also be sure to pour excess amounts of varnish since it flows a bit differently than Collodion. Drain into separate bottle and let stand for at least a minute so that the alcohol evaporates. Then reheat until it starts to smoke (this is when it smells good!). Let sit still for at least a day to fully set. When pour-off bottle is full, filter and add 10-20mL alcohol to compensate for evaporation.

Sandarac Varnish Formula:

95% Grain Alcohol - 360mL
Gum Sandarac - 50g
Lavender Oil - 38mL

Pour the alcohol into a glass bottle. Fully dissolve the gum sandarac into the alcohol by vigorously shaking the bottle (this may take a while). Once dissolved, filter through coffee filters. Finally, add the lavender oil.



Wet Plate Holder:

For my wet plate holders, I use regular film holders that have been modified to accept plates. The modification is fairly simple to perform. First cut out an area slightly larger than the plate size you will use. Then superglue little triangles to the corners on one side. This side will be the side facing towards the lens. To use, place your plate on the opposite side of the glued triangles (loading side). Then, use a "spring" made from a milk jug or plastic container to back the plate. If shooting a tin plate, back it with a glass plate so that the plate will not bow under the pressure of the spring. Slide in the darkslide while holding the spring in place. Make sure both darkslides are in place. You are now ready to expose the plate. The UnBlinkingEye also mentions how to make a modified holder.


Above: The front side of the modified holder (this side faces towards the lens).


Above: The back (loading) side of the modified holder.




Above: A handmade folding plate drying rack.



The formulas that I used here were from the UnBlinkingEye .

Collodion forum

Bostick and Sullivan - Source for wet and dry plate supplies in the US.


Old published manuals and books:

Carey Lea

Old Wet Plate manuals

The Silver Sunbeam

The Ferrotype and How to Make it

Modern Practice of Photography

Treatise of Photography on Collodion




Contact: Tai Oliphant

Copyright © Tai Oliphant 2012