[photolytic]

Andy,

There appears to be no optimum distance but the distance in most boxes seems to be 3-4 inches simply to reduce the size of the box to a more manageable size. My measurements in the attached graph were made by sampling 100cc of the vapors at the top of a closed box using a syringe.

The iodine was extracted from the vapors with ethyl alcohol and titrated with a standard solution of sodium thiosulfate using starch as the indicator.

I repeated this at several temperatures and found that the measured iodine concentration in the vapor was 4 orders of magnitude (1/10000) less that the theoretical concentration for iodine vapors above iodine crystals at that temperature.

I also did this for bromine vapors using a fuming box containing 10 grams of bromine mixed with 400grams of calcium hydroxide. In the case of Bromine I found that its concentration was also approximately 1/10000th of the theoretical concentration for bromine vapor above bromine liquid at that temperature.

[photolytic]

Resublimed iodine is just iodine purified by sublimation (distillation from the solid state).

Outgassing as you call it is nothing more than sublimation. The amount of sublimation is primarily controlled by the vapor pressure of iodine which is a well known function of temperature. The rate of sublimation is proportional to the surface area of the iodine crystals and can be increased by grinding up the crystals to a fine powder.

In a confined space sublimation will stop when the partial pressure of iodine vapor in the air above the crystals reaches the vapor pressure of iodine and equilibrium is reached. Because iodine vapor is more than 8 times heavier than air, it tends to stratify unless the air is stirred up, so that the concentration of iodine vapor at the top of a fuming box may be a several thousand times lower than at the bottom of the box near the crystals. As a result fuming takea longer if the the distance from the iodine to the plate is greater or if a barrier or membrane is placed between them.

To ensure uniform silver iodide coatings, fuming is usally done when the concentration of iodine fumes in the box have reached equilibrium. This may take only a minute or so if the temperature is above 20C.

In his paper on iodizing Daguerreotype plates, Irving Pobboravsky reported that iodide coating thickness (XRF) increase linearly with time up to 180nM during a over a period 7 minutes. From the density of silver iodide it can be calculated that more than 20 mg of Iodine will have reacted with the silver on the surface of a wholeplate during this fuming. Thus it is important that during long fuming period sufficient intervals for iodine fume renewal be allowed.

[photolytic]

Good idea Gregory.

Use a very light touch, or this will leave scratches and an alcohol haze on the plate.

A dry method is to follow the rouge buff with a longer lampblack buff before your clean buff.

Also it’s a good idea to keep notes of buffing conditions so that you don’t have to reinvent the wheel.

You never know when sniffing too much iodine will wipe out your memory.

Cures Goiter though.

[photolytic]

Thanks for the silver plating info Mike. Take 2 aspirin and call your doctor in the morning.

The Mathematical relationship defining plating is Faraday’s law which can be summarized by:

m = (Q)/F) x (M/z)

where

m is the mass of the metal deposited at an electrode

Q is the total electric charge (electrons) passed through the metal solution.

F = 96,485 mol-1 is the Faraday constant

M is the molar mass of the metal which is 107.88 gm/mol for silver

z is the valency number of ions of the metal ( 1 in the case of silver)

Note that M /z is the same as the equivalent weight of the metal deposited.

For Faraday’s second law, Q, F, and z are constants, so that the larger the value of M / z (equivalent weight) the larger m will be.

In the simple case of constant-current electrolysis, Q (coulombs) = electric current in amps (coulombs/second) x time t (seconds)

For a full plate (area 356.45 cm2), a 25 micron (.0025cm) layer of silver (10.49 gm/cc) weighs 9.348 grams and contains 0.08665 moles of silver.

0.08665 moles when multiplied by Faraday’s constant (96485 Coulombs/mole) will require 8360.5 coulombs or 2.322 amp hours of current or 2.322 hours at 1 amp. The efficiency of silver plating is not 100% but is typically closer to 70% due to other reactions that may also occur in the plating bath. Therefore the actual plating time would be closer to 3.3 hours.

As Mike has noted, modern silver plate is harder that the “galvanized” plate of the 19th Century due to higher current densities and the addition of brighteners to the plating bath.

It should be noted that while the Elkington brothers invented the electro-plating process in 1840, as early as 1847 Elkinton’s workers discovered that by adding carbon disulfide to the silver bath the silver deposit could be made brighter and more coherent. This made electroplated silver suitable for the Daguerreotype process and shortly thereafter electroplated Cristofel plates became available. Carbon disulfide is still used today by some silver platers

Since Daguerreotypists did not need to add any brightener to their plating baths because the “Galvanized” layer was relatively thin, the silver layer on a galvanized plate is not as hard as that of a commercially electroplated plate

[photolytic]

Thanks Jason. Perhaps you need to exercise more control over your silver platers operations. Your contract with him should specify how much silver you expect. Silver is quite heavy so it is relatively easy for you to measure the silver on the plates by weighing your polished copper plates before and after the plating. Stopping out the back of the plates will insure that this silver is definitely on the front of the plates. If you have not already done so you should invest in an accurate digital scale. Its initial cost will be paid back many times during your Daguerreian career. In my last silver plating job the cost of the silver alone was more than $500.

[photolytic]

[Don’t use Nushine with electroplated silver, it will cut through the thin layer of silver exposing your base metal.]

Notwithstanding the excellent Daguerreian credentials of igmotamed; I believe the above quote somewhat overstates the danger here. Good electroplated plates with 25 microns of silver are just as durable as clad plates with a similar silver layer, and even at the current silver price of $30/oz; they are an attractive economical alternative. That being said, silver is silver and it should never be polished with anything suitable for polishing harder metals. While users of NUshine recommend it for polishing silver or gold plated musical instruments, others suggest it is sufficiently abrasive to polish nickel and chrome automobile parts. As always. caution is necessary when polishing Dag plates, regardless of their manufacture.

[photolytic]

There may be previous posts on this subject.

Check the reference section also.

Have you tried looking yet?

Making Dag prints is just like making silver chloride gelatin prints.

Just don’t slide the Dag plate or transparency around or you will scratch the Dag plate.

As with the paper prints, you need to make test exposures to find the correct exposure.

You can use a regular incident light meter to measure the strength of the light coming though the transparency. Then, if you are familiar with optics, you can calculate the intensity of light hitting the film plane inside your camera. Or you can just stick your light meter inside your camera and measure the light you use to make an in-camera Dag.

For a first approximation, you can neglect the difference between UV and visible light here. Dags are sensitive enough to both blue and UV. Even if your light source is a regular incandescent bulb it has enough UV do the job. Use a blue photoflood bulb if you need lots of light for a Becquerel Dag.

You don’t mention the equipment you have but depending upon the strength of the light source, the exposure could vary from a few seconds to several minutes.

Sorry if that’s not precise enough for you, but you need to provide more info.

[photolytic]

Regarding the statement above:

“But then again my strike-through box isn’t any better, as iodine accumulates on the slide and leaks when it is shifted.”

It is physically impossible for solid iodine to deposit of the underside of the tray of the slide-through fuming box, or any other box design for that matter.

Due to the high density of the iodine fumes and the absence of any stirring, the actual measured concentration of the iodine fumes, 8 cm above the crystals (0.00001m/1), is one thousand times lower than the concentration necessary for any iodine to sublime onto any surface which is 0.01m/l at 20C. (International Critical Tables) Any iodine solid there would have to be the result of the box having been inverted or violently shaken before fuming.

As to escape of iodine fumes, the space between the bottom of the Galasso box Tray which is in contact with the glass tray, and the bottom of the plate holder tray is only 3mm, making the volume of iodine fumes trapped there only 107cc, which at a concentration of 0.00001 m/l, contains less than 0.00027 grams of iodine, most of which is still reacting with the silver plate until it is removed from the tray.

Bravo!

The drop down design of the tray when the glass slide is removed, which was mentioned above would greatly mitigate any fume looses. I am a bit concerned that the shock of the drop might damage the lip of the glass tray and the force of the air pushed into the top of the tray might cause eddy currents in the iodine fumes which would take a while to die down. If the bottom of the tray were lined with some inert cushioning material like Teflon, that would eliminate the shock problem and make sliding easier.

[photolytic]

With the strike through design the glass tray is covered 100% of the time either by the back end of the drawer, which is glass, or by the front end of the drawer which is wood and a plastic insert which holds the silver Dag plate.

With the slide construction there is an interval, however short, when the slide is withdrawn, leaving a gap between the glass tray and the drawer through which fumes may escape from the tray. Leaving the slide withdrawn for the entire fuming cycle only makes this situation worse.

[photolytic]

TY,

Sorry, but I didn’t need new boxes and didn’t want to spend another $1000 for a second pair.

Many on this site like your design and you should make and sell a lot of them to this market.

Many don’t consider extra time or manipulation a problem. Maybe after making thousands of dags for a decade or so and developing arthritis in their old age they will. I only wanted to point out what I have found to be beneficial in the slide through design. As a chemical engineer I’m a big proponent of the total confinement of polluting chemicals approach as opposed to the “blow it up the stack” approach and the strike though design comes closest to this goal.

I think what is really needed is a box with a glass liner for plate sizes larger the wholeplate. Any plans?

[photolytic]

To construct stops for the glass slide you could add wood strips along each side of the glass plate with a downward protruding ridge at the end which would catch on the wooden front of the box thus preventing complete withdrawal unless the screw mechanism on the top is removed first.

The side wooden strips would also add extra strength to glass slide so it would not break if it was inadvertently pushed down too hard. Alternately you could glue small Plexiglas blocks to the underside at the far corners of the glass plate

If you leave the slide out between plate fuming steps you save operations and time but there will be no seal to prevent fumes from escaping the box during this period. As a result you will need to wait between fuming cycles for the fume concentration at the top of the box to be restored.

If you do push the slide back in after each fuming cycle, which typically last only 4 seconds per cycle, the plate will continue to react with the fumes trapped between the slide and the drawer until the drawer is withdrawn. Even if this operation takes only an extra 2 seconds, the plate exposure to the fumes could be increased by as much as 50% per cycle. Depending on the overall fuming time, a 50% fuming increase can have a significant effect on plate sensitivity, image contrast and highlight solarization.

Because the density of iodine fumes is 8.8 times that of air, the concentration of iodine fumes at the top of a Galasso slide though box, which is approximately 8 cm above the iodine is only 0.00001m/l or 1/1000 of the concentration the fumes on the iodine surface, which is approximately 0.01 m/l at 20C. Adding extra distance between the top of the glass tray and the plate drawer will further reduce the concentration of the iodine fumes reacting with the plate. Thus it is important that the top of the glass slide be very close if not flush with the bottom of the plate drawer.

[photolytic]

In the multiple fuming process, the plate is first fumed over iodine, preferably in 3 to 4 stages so the color change can be visually monitored. Each stage requires 2 steps (in and out again) for the slide-through design and 2 more if the box is equipped with a glass slide for a total of 4 operations per fuming stage. For 4 iodine fuming stages this amounts to 16 operations for the first iodine fuming alone.

Then the plate must be fumed in the bromine box in 3 to 4 stages for a total of 6 to 8 stages until the desired color is obtained. This adds as many as 16 more operations for a total of 32.

Finally the plate must be returned to the iodine box for 2 more stages, one in white light and the second under a safelight for a total of 8 to 10 stages per plate. This adds another 8 operations to the total fuming process for a grand total of 40 operations per plate.

My comment was about the glass slide not having a stop. I didn’t realize that the plate holder had no stop either. Both should be equipped with stops to prevent them from being pulled completely out of the box.

[photolytic]

The strike-through design does not leak at all when not in use and almost none when it is in use. It does emit a very faint odor of bromine as the drawer is withdrawn and hence should not be placed in the same hood with your mercury box. Even a faint exposure to halogen fumes will destroy or weaken the latent image before the mercury has a chance to do its job. I9th Century literature recommends this to correct for accidental overexposure. I always keep the fuming boxes in a separate room from my mercury developing apparatus to prevent such an occurrence.

If you can’t accommodate a fume hood large enough for a strike-through fuming box, I suggest performing the fuming operation without a fuming hood as I have done for 13 years.

After you have raised 3 kids using cloth diapers, which have to be soaked in Clorox, the fuming box odor is very faint by comparison.

Eliminating the need for an extra 10 box manipulations per fumed plate has saved me 35 thousand extra steps during the fuming of over 35 hundred plates during my Daguerreian carrier. Remembering to perform that extra step of withdrawing the slide is sort of like remembering to remove the lens cap on your 35mm camera. An occurrence that happens to me all too frequently on my rangefinder camera.

[photolytic]

What prevents the slide from being pulled out all the way when it is withdrawn?

I don’t see a stop at the far end.

Also the slide plus drawer design requires 4 steps for each plate fuming operation instead of two.

The first one to push the drawer in, the second one to pull the slide out, the third to push the slide in again and the forth to pull the drawer out.

Uniform fuming requires rotation of the plate between fuming operations so the drawer must be pushed in and out and the slide must be pushed in and out for each fuming operation.

As many as 10 fuming operations may be required for each plate, so this adds a lot of extra manipulations to the fuming process.

[photolytic]

As an experienced wet collodion photographer, I suggest the comparison would not be as easy as it appears. You’ve got a lot of extrapolation to do.

Fast wet plates have speeds up to ISO 1.5, or about 8 stops faster than B-Dags.

Also collodions containing bromide salts have significant sensitivity to green.

I’d suggest using a B-Dag test strip with a series of exposures on one plate to zero in on the best exposure. To determine the starting point in “variable weather” I’d advise using an exposure meter.

For UK experience you might contact David Burder in London at burder3D@AOL.com

[photolytic]

If you are only making BDags you should save your money and buy a really good, glass lined, fuming box for your iodine. As Ken (Mercury) Nelson recently posted “My sensitizing boxes release such a tiny amount with each slide that we never smelled it, and iodine and bromine are odious at infinitesimal levels.

Iodine vapors are 8.8 times heavier than air and as such they tend to concentrate near the bottom of the fuming box. I’ve measured the concentration of the iodine fumes inside the top of my box and found them to be less than 2 ppm at 20C. Very little of this iodine escapes during the fuming operation. Only the last few seconds of fuming needs to be done in the dark so you can keep the shed door open for the initial fuming.

If you keep your shed door slightly ajar to improve the ventilation your iodine fumes should not be a problem. You may want to install a vent fan in the shed to improve the air flow.

Keeping the temperature and humidity in the shed may be an even greater problem as both affect the rate of iodine fuming, not to mention your comfort and health.

These occupational Exposure Limits (NIOSH, 1997; ACGIH, 1994) can be found at

http://oehha.ca.gov/public_info/pdf/TSD%20Iodine%20Meth%20Labs%2010’8’03.pdf

1. Ceiling Limit (C) (not to be exceeded at any time): 0.1 ppm (1 mg/m3)

2. Short-Term Exposure Limit (STEL or ST): Not established.

3. 8-Hour Time Weighted Average (TWA): Not established.

4. 10-Hour Time Weighted Average (TWA): Not established.

5. Immediately Dangerous to Life & Health (IDLH): 2 ppm (21 mg/m3)

In air, iodine vapor will be hydrolyzed by water vapor to iodate (IO3

?) and iodide (I?) ions, which have a relatively low order of toxicity.

[photolytic]

I’ve had my glass lined iodine box in my house for 13 years. It has not lost any iodine. There is some discoloration of the blond colored wood but no odor. You must have the boxes inside and warm (20C) to get reproducible fuming times. If you are not going to be using the box for a long period of time, take the iodine out of the box and put it back in the bottle.

After all you cannot count on a fume hood to run unattended all the time without breakdown or power outage. Most Daguerreotypists only turn on their fume hoods when they plan to fume or heat up the mercury pot. Fume hoods should not be considered reliable enough for long term storage of toxic chemicals.

If you are worried about your lack of knowledge concerning the handling of iodine you should not even consider making M-Dags until you take a workshop or a chemistry course somewhere.

[photolytic]

You probably don’t need a fume hood for B-Dags.

So long as you fill your iodine fuming box outside the house, your exposure to iodine fumes will be minimal.

Although the theoretical concentration of iodine fumes directly above iodine crystals at room temperature (20C) is about 360ppm, based upon Iodine’s room temperature vapor pressure of 0.275 mmHg, my measurements indicated that the actual concentration of heavier than air iodine fumes at the top of my fuming box was only 0.13 parts per million, less than the 2ppm chlorine found in the average swimming pool.

http://www.healthybuildings.com/images/sce/design/Swimmers_asthma.pdf.

[photolytic]

Have you have tried a collodion positive on a front surface glass mirror?

They have poth positve and negative images just like a Dag.

[photolytic]

Only you can judge whether or not the B-Dags you get will satisfy you. The effort it takes to get started making good B-Dags will not be wasted as most of the same equipment and techniques will be needed to make M-Dags anyway. Judging by the reports of other beginners on this site, many are thrilled with even the most rudimentary images at first and some subsequently give it up entirely, having satisfied that primal urge to make a Dag, before going on to something else like making fake, digital Dags.

[photolytic]

Wiil this also work with invisible infrared light?

Take your best shot here because I already know the answer.

 

If you give an iodized plate a second camera exposure, the yellows and greens in the subject should also start to should show up more strongly in the image.

Has anyone given such a pre-exposed iodized plate an exposure to a color chart to see if this happens? I don’t mean hypersensitizing which presumably affects all the colors equally.

 

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[photolytic]

When a total of 3 photons of high energy blue light have hit a molecule of silver iodide, it splits into silver metal and iodine. This happens in the camera exposure for both mercury and Becquerel Dags. The mercury forms amalgams only with these silver atoms formed during the exposure (latent image) plus those formed during the plate fuming process while the lights are on (photolytic silver). Mercury does not “react” or reduce any silver iodide as happens when ordinary film is developed with a reducing agent such as hydroquinone.

In the light spectrum the wavelength of red light(625-740uM), is higher than the wavelength of blue light (435-500uM). In the Becquerel process, exposure to high spectrum red light does not have enough energy to cause more silver iodide the break up, but it does have enough energy to somehow cause these molecules of silver to vibrate and move around. When the silver atoms collide they form the larger aggregates of pure silver that make up the image. The unaffected silver iodide dissolves in the fixer as with any silver based film.

[photolytic]

Speedotron accepts several different reflectors.

You mentioned using a 22inch model whereas I used a 20inch aluminum reflector.

I measured the distance from the end of the tubes inside the reflector.

It is important to hook up the cables, one to a center 2400ws socket and one the a combined 800/1600ws socket located on the left side of the 4803 power pack. If you hook both cables up to the 2400ws sockets you only get half power.

[photolytic]

I tried my Speedotron 4-tube no 105 flash head at 9600ws using 2 Speedotron 4803 power units today. Speedotrons guide number is 720 at ISO 100. Multipling 720 by the ratio the 10 aperture stops between ISO 100 and the ISO 0.10 speed of a Daguerreotype or 1/32 predicts a Dag guide number of 22.5 at 9600ws.

 

This plate was shot at f/3.5 with the 9600ws unit at a distance of 6.7 ft (2m) or guide no 23.

 

 

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[photolytic]

I’d be interested also.

John Hurlock

[Author]

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