Second iodine : how many time?

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    Hello everybody,

    First of all, sorry for my poor english, I come from France.

    I use bromine for only a few month (with many problems), but this is not the subject of this message.
    In the process, it’s always said that it’s necessary to put again the plate into iodine box after bromine.

    I do that, off course. I put the plate for 20 seconds (time chosen almost by… chance, following the time found by others) for second iodine. But I never tested what’s happen if I let the plate more or less than 20 seconds. How does it react? Is speed changes? Contrast?

    What kind of result I am supposed to find on the plate with the good time?

    Thank you for your help!



    Are you formerly from Portugal like your famous namesake explorer Tristão da Cunha?

    As for me I am the one from Chicago who wrote the article to which you refer in your 23 April blog as “Un ricain a fait toute une thèse là-dessus ( à lire sur ) “.

    Any time over the second iodine down to 2 seconds will do. You can do several times on the same plate by masking part of the with glass over the iodine box. Generally the more time, the lower the contrast and sensitivity



    Hello Photolytic,

    Thank you for reading my blog! I thought I was the only one to read it! I’m happy to discuss with the man who made that incredible study about hypersensityzing plates. It was very high grade level, and unfortunately, my english level wasn’t not good enough to understand everything. But I loved it.

    I have the same name than the famous explorer but it’s a chance. My family doesn’t come from Portugal, but from Brazil (same language).
    The first to live in France, it was in 1910. He created the french part of my family from that point. There is no more link with the brazilian part since at least 80 years.

    About our topic, I did a test just a few minutes ago, in order to see myself what’s going on.

    I put half of a plate for 20 seconds into 2nd iodine. And the other half for 45 seconds.
    And the result is surprising : none difference. It’s even difficult to see what is the 20s’s part from the other one.

    I’m happy to discover this, because it’s a problem I can forget! So, I continue with 20 seconds.

    And, again, thank you so much to give your time to help me!



    Another question : why is it necessary to put a second time the plate into iodine after bromine?
    What happens if the plate is done without 2nd iodine?



    Because the bromine fuming should be done under weak white light which produces photolytic silver that increases the speed of the plates. As you know the dag developing procedure does not reduce any silver halide like in b/w film for example. The metallic silver in the image comes from the action of the light in the camera plus the action of light during the bromine coating inspections. If you do all your bromine coating in the dark your plates speed will be slower. You should read Barger and White’s book to familiarize yourself with how the process works before you experiment further.
    The second Iodine is done to restore the sensitivity of the plate to camera exposure light. The times you are using (20-45s) are much longer than is need for this purpose unless your iodine temperature is very low. (<10C)
    Most suggest that the second Iodine should be half as long as the first iodine. Part of the second iodine should be done under white light so you can see the final color of the coating. Only the last 2 to 5 second needs to be done under safelight conditions or in the dark.



    Thanks for reply, Photolytic.
    This is very technical, and very interesting… Such a knowledge, I’m impressed. This is great.

    At the beginning of my tests with bromine, I did my bromine coating at light. But I stopped, because of a contrast’s problem on the plates. I was afraid it was due to action of light… I realized my mistake later : the problem cames from too much bromine wich created haze on the plates.

    From this time, I sensitive my plates in darkness after bromine. And you’re right : I noticed a lower speed than Pobboravsky Exposure Guide. Almost 1 stop is always missing.

    Another mistake from me… So, I’ll do my bromine sensitive at light for next plates.

    But you wrote my time is too long for second iodine. It should be half as long as the first iodine.
    I’m surprised, because my first iodine time is comprised between 2 and 5 minutes to reach strong yellow for the first cycle (between 20 and 26°C). So, 20 seconds doesn’t seem to be too long.

    You wrote : Part of the second iodine should be done under white light so you can see the final color of the coating Why is it so important to see the color of the plate at this last point?



    You should get 1st yellow (Not a very strong color) in 10 seconds at 20-26C.
    You are probably going to the 2nd yellow at 2 min and even 3rd yellow at 5 min.
    How much iodine do you have in your box and what are you covering it up with?
    Maybe the iodine fumes are having trouble getting through to the plate.

    The effect of bromine on the color of the plate is very subtle and is only obvious after a fresh iodine fuming.
    If you want to get reproducible results you need to keep notes of the temp,fuming time,and plate colors at all stages.
    Only then can you understand why you are getting different results at different times.
    Here are the colors of the first cycle of iodine fuming.
    If you see colors other than yellow before you get to a strong yellow you are past the first cycle.

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    Same with times attached.

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    Thank you so much for sharing your knowledge.

    Your result is very surprising! I have none color after 10 seconds into iodine. Color changes very slowly, minute per minute.
    After one minute, I get a very light yellow color, getting stronger after 2 to 3 minutes. Pink color arrives after that.
    The blue color comes after 6 minutes at least.

    I noticed that color is always stronger ont the edges of the plate VS the center. It is said it’s a normal phenomenon. Is there a simple way to fix this (I’m too lazy to use Daguerre’s method, who used silver pieces all around the plate!)?

    Just before putting the plate into the iodine box,I use a hairdryer to warm the plate.

    I put iodine (half of a glass) into the box, and I cover it with paper handkerchief.
    The iodine and his paper are always into the iodine box. But they are into a plastic box (at the bottom of the iodine box). I put a plastic cover on it when not in use.
    It’s a way teached by Marc Kereun, a famous daguerreotypist here in France. He prefer to have the time to see slowly changing colors onto the plate. Is it a mistake?

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    Mark Kereun is a very dear friend and I greatly value his suggestions.
    I’m not sure what Marc’s fuming box looks like. so my suggestions are based upon the design of my fuming box .
    The edge to center iodine color effect should not be a big factor on a well polished plate in a good box.
    To distribute the iodine fumes better they should be placed in a flat glass tray,like a cooking dish, not a tall glass.
    For long term storage the plastic box will be attacked by iodine fumes and leak.
    It is better to have a glass lid, etched like camera ground glass, which slides over the glass iodine tray.
    If the iodine box is fitted with a spring pressing the lid down the fumes can not get out.
    The color change leading up to first yellow takes place rapidly and can be observer at intervals of a little as 2 seconds. It takes time for the iodine fumes to become distributed through out the box.
    The fumes are heavier than air. I sampled the iodine vapor from the top of my box near the plate fuming area, using a syringe and found it contained ten-thousand times less iodine than the concentration at the surface of the iodine crystals as predicted by the vapor pressure charts. Fuming can easily deplete the iodine fumes at the top of the box and Pobboravsky found that it is better to wait between fuming events for the fume concentration to be restored.

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    Thank you!

    Very impressive work!

    I did my first dags with Marc. He uses a very simple box (it’s a wine box, made from wood), same size than mine. He uses the same plastic box inside.
    It’s true that iodine vapors attacks plastic. But not so fast. Since 2 years I have mine, the inside became black, but not destroyed. It’s still in good condition.

    If my box goes too slowly, I think it’s not so important if the result is reached all the same?

    I did another plate today. Since several weeks, I still have 3 boring problems on all may plates :
    – White and black spots. Now, I understand it’s due to my silver supplier who probably use alumine powder. For the future, I’ll try to find another one. For the moment, I must continue to use those I have, and I’m angry, those spots are simply horrible.

    – Sometimes, I have haze (only on some parts of the image, not all surface), due to too much bromine. I use bromine water. (Because I don’t want to have pure bromine into my lab, too dangerous.). But it seems to be very difficult with bromine water, even while using always the same quantity and time. I did many tests to find the good time. Each time, I think to have found the good one, and unfortunately, I’m wrong.
    I think to use soon bromine with silica gel, like Mike Robinson. I hope to fix the problem by this way.

    – Still have between 1 and 2 stop missing speed on the images. (VS Pobboravsky’s exposure guide).

    I did a new test today, and I followed your advice to let the plate receiving light after bromine. You’re right, it seem to be a bit better for speed.
    See the file attached. I’m desespered with the result! Spots, haze (and not the same speed all over the plate), underexposed… everything is bad.

    My big problem, it’s bromine.

    I’m only 2 years of practice, I realize I can spend all my life doing tests. Nevertheless, I hope to have a good result one day!
    It’s strange, because when I began, using only iodine, I had better results. Bromine is very difficult to use!

    You must be logged in to view attached files.


    Another test…
    I chose to overexpose 1 stop, following Irv’s exposure guide. It’s still a bit dark. Half a stop more would be better.
    The right of the plate begins to be overbromated.

    You must be logged in to view attached files.


    Do you rotate your plates during fuming?
    Uneven fuming can be reduced that way.

    I see that you are now getting more black spots than white ones on your plates.
    You should increase the buffing time or put fresh buffing material on the Random obit buffer to try to eliminate them.
    I buff a 13x18cm plate for at least 15min at the lowest speed on the ROB.

    The space between the top of your iodine dish and the sliding lid is too great allowing much of your fumes to escape.
    Try putting something underneath the dish to raise the level closer to the top of the box.

    I see that you do not have enough iodine crystals to cover the bottom of the tray in your fuming box.
    A whole plate fuming box should have at least 200grams of iodine. Mine has 400grams.
    If you make these changes it would shorten your fuming times.
    You say that the longer fuming time doesn’t matter so long as the same color is reached.
    However consider this:
    The advantage of shorter over longer fuming times is that it makes it easier to remember the progression of the colors.
    After a long interval, your memory of the previous color fades and everything begins to look the same.
    Longer times make it easier to pass over that narrow window of colors that produces the fastest plates and best tones.

    The pronounced bluish color of your images may be because of the moisture in the bromine water.
    Dry bromine will lead to more neutral colors.
    Remember that you must keep any silica gel mixture in a sealed container away from moisture of it will absorb water.



    I learn much more by reading you than everything I read since years! Thanks again and again for sharing your great experiment. It’s so precious.

    During bromine fuming (20 seconds) : yes, I rotate the plate one time, at half of the total time.
    Actually, I suspected moisture of the bromine water to be responsible of my troubles.
    And I understand now why I had blue tones on my plates!

    So, I would try to use silica gel, but you say it’s important to preserve it from moisture. I wanted to use my bromine water to saturate silica gel : I understand it’s a mistake. I can’t do that, because moisture into the water will be absorbed by silica gel and destroy the benefit.
    I’m afraid to introduce pure bromine into my lab. My bromine water stink already a bit, because odour goes through the cap of the bottle, even perfectly closed. I put it into another container, but the odour continue to go away. If I use pure bromine, it would be worse. I don’t know how to store it with a good safety level.

    About spots : I buff at least 5-7 mn with my ROB for each part of polishing : rouge, lampblack, and pure ultrasuede.
    But before rouge, I use a polishing dough (on ultrasuede with ROB) very efficient to remove scraches. Then, I clean the plate with water and dish soap. I dry the plate with air compressor. I know this part is my invention, I hope it’s not another mistake.

    So total time is at least 25-30 minutes. Your advice is to continue longer. Ok, I’ll try it. But if my plates are not well silvered, I’m afraid it’s unusefull work.

    A question : how do you remove a failed image from the plate prior to ROB? With the rotary buffing machine and rouge?

    For iodine box : I’ll try too to put more iodine into it and reduce space between iodine and the plate holder.



    What is the composition of your polishing dough?
    Be sure it is for silver, not the base metal type and does not contain alumina.
    The air from the air compressor contains moisture and perhaps some particles.

    The rotary buffer will remove the scratches better. Afterwards you can clean up the plates with alcohol.
    Before gilding the failed image can be removed with a light wipe with a soft dry facial tissue.
    The rotary buffer with rouge will do the rest. Then use the ROB.

    What type of plate holder do you use on top of your iodine box.
    Do not use the camera plate holder as the residual iodine fumes may be absorbed and erase the late image.



    A recent sensitizing time:

    I Box: 300 g. Iodine in glass baking dish with a single layer of polyester batting (upholstery padding) to diffuse fumes. I use a ground glass cover on both fuming boxes.

    B Box: Liquid Bromine in silica gel with single layer of polyester batting as above. Gel is light yellow in color.

    (Can provide Bromine prep details later if you wish)

    Air Temp: 22 deg C
    RH: 60%

    First I: 30 seconds- light rose (just after first yellow); plate rotated 180 degrees after 15 seconds
    Bromine: 6 seconds – determined using “strip” mask on test plate at 2,4,8,16 seconds
    Second (Healing) I – 5 seconds

    Exposure in bright sun (EV=16) at f11 was 8 seconds

    I use a hand-squeezed air bulb for dusting plates- I found “canned air” created marks, and I know my air compressor air has oil and dust in it.




    To answer to Photolytic :
    – My polishing dough doesn’t contain alumina at all. I wrote to the supplier, and he confirms.
    More and more, I’m convinced that my spots comes from a problem during silvering. I found a new supplier, and I’ll try it soon.

    My plate holder, on my fuming box is made from little corners of plastic wich maintain the plate. I don’t use camera plate holder.

    For Nawagi : thanks for your answer!
    I’m interested for providing prep details from you!

    For bromine into silica gel : I’m afraid to use pure bromine into my lab. Vapors are too dangerous. I’m already very afraid to use my bromine water, because of the smell. I don’t have the same felling with iodine and even mercury.

    I have a good fume hood and a professionnal mask covering all the face. I don’t smell anything during using it.
    But my problem is : how do you store safety bromine without any odour, between two works?

    My bromine water is in a glass bottle with plastic cap, and it stinks into my lab. When it’s cool, it’s OK, but during summer, with high temperatures, it becomes to be dangerous. So, I add another glass container to reduce odour. But after a few weeks, it stinks again. I don’t have any solution.

    I hate this odour. I’m afraid with it. How do you solve that?



    Do you ever a swim in a chlorinated pool?
    Bromine is frequently used to replace chlorine as a disinfectant in pools and spas.
    Those with very sensitive skin may prefer bromine because it generally does not cause as much skin and eye irritation as chlorine sometimes can.

    Excess bromine fumes can be reacted with thiosulfate. Place the Br/water container inside another airtight container with a tube leading to a container of sodium or ammonium thiosulfate. Alternately an airlock such as those used on wine
    barrels with thiosulfate in the air trap can be used. Do NOT try to neutralize the fumes with ammonia. Halogen fumes (especially iodine) can react with ammonia to form nitrogen tri-halide compounds which can are explode.

    Unlike mercury which has no odor to warn you, the odor of bromine is your friend, warning you to avoid breathing the fumes before they reach a dangerous level. The plastic cap on your bromine bottle is probably not resistant to the fumes. Several other writers on this site have found Teflon lined caps that are more effective and resistant to bromine.



    Sincerely, thank you again for you help. This is securing me.

    So, can I use this way : putting my bromine bottle into a bigger glass container wich contains crystals of sodium thiosulfate in it? It’s easier to do.

    I already use sodium thiolusfate delayed in water to wash my instruments contaminated by bromine. It works very well.

    You’re right to write that the odour is also a friend. It’s a signal wich permits to worry and react.

    I note your advice to use Teflon cap to seal the bromine bottle.

    About my problems of homogeneity with bromine, someone here told me that my bromine box is too big for good result. He says it’s impossible to have good results with a so big box. I should use a box the same size than the plate. And I should not use wood, wich absorbs bromine (too dangerous).
    What do you think about that? Should I make another one? It’s boring me, because I spent a lot of time to do it!

    Thanks a lot!



    Using hypo crystals is a good idea, much easier.
    Your local advice is correct. Your Bromine box is too big and the space between the bromine and the plate is too great. My wholeplate box is only 7cm deep and the glass bromine dish fits all the way to the ground glass seal at the top.
    It is too much work to build a new box for every plate size. Build your box with a hard plywood (Oak or Birch)for the largest plate you want to make in the future. In a cooking supplies store find a 5-6cm deep and rectangular glass dish that is just large enough for your intended plates (approx. 18x24cm for wholeplate). Build your box slightly larger to fit the glass dish. You can always add wood shims or a bottom board to make the dish fit exactly later
    Sand the top edge of the dish flat so your sliding glass sealing plate fits it. Add some silicone grease to the top of the dish so it makes a good seal with your glass sealing plate.



    Thank you for those advices.
    I’m going to adapt my box to reduce volume inside. I won’t make an entire new box again.
    I do that, then, I’ll be back for the results!



    Nawagi said : Exposure in bright sun (EV=16) at f11 was 8 seconds
    I obtain the same speed, more or less. So, my method seem to be quite good.

    But I’m surprised with Pobboravsky’s exposure guide : I never reached the speed of his guide. If I follow the guide for 0,05 ISO speed, it’s always underexposed between 1 or 2 entire stops.
    I have good results around +1,5 or even +2 stops.

    But it’s not so simple, because I noticed different point of view between daguerreotypists. Some of them hate to solarize parts of their plates, so they underexpose in order to have correct tones. But the problem is following : their images are not easy to see on the plate (too light).

    For my own, I prefer overexpose a bit, in order to have a strong image, easy to read for public, even if parts are solarized. So I prefer measuring exposure for shadows (a bit, not entirely).



    I agree with your exposure method.
    I expose for the medium shadows or average between the highlight and the dark shadows.
    I let the sky solarize to a medium blue.
    It looks good and the image is strong enough to see in public with good angled lighting.




    I followed your advice and I put my bromine bottle into a sealed glass jar, with hypo crystals inside.
    It works very well : fumes totally disappears into the jar. It’s so effective I’m afraid those crystals destroy bromine into the bottle!
    I’m looking for a PTFE cap for my bottle.

    I did a new test today, by reducing considerably the volume into my bromine box. I removed 70% of the volume inside by making a “cap” of the good size.

    The glass jar containing bromine water is now 6 cm from the plate.
    The result is fuming time becomes extremely short. I did a test with 5, 10, 15, 20 seconds.
    Even at 5s there is an image. Good time is 10 seconds.

    But I still have haze on some parts of the plate (see the brown one on the tree). Is it due to moisture?

    So, reducing the volume of the box is not so effective. It’s just faster.

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    Those 5s -20s bromine times are typical for 20C fuming.
    I use 8s -12sec.
    Longer first iodine times require longer bromine times.
    I don’t know what caused the brownish spot.
    Was your fixer fresh?
    Did you wash the plate well before drying it?
    If you gilded the plate, did the gilding solution dry out on that area of the plate or get too hot?

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