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Your silver plates seem to require much polishing and cleaning before the rouge/velour stage
Does your plating solution contain a brightener?
Are the silver plates dull before polishing?
I would avoid Nushine silver polish as it contains thiourea that has been demonstrated to cause staining on Dags.
If you do a dry polish with stick rouge you will not need mineral spirits and soap (really! saponified fat?).
Only a light alcohol wipe with an ethanol soaked facial tissue (use lotion free type) will be needed.
http://rkm-ltd.com/products/silver-polish/

After the rouge/velour polish you should use a lampblack/velour to remove the residual powdered rouge.
Finally you should use clean velour (velvet?) to remove all lampblack or it may cause black spots.

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Alan’s points are well taken.
High bromine levels may increase the ISO speed but also reduce the contrast and cause haze.
Reducing the bromine exposure a bit will increase the contrast but still leave you with a speed you can accept.

You don’t mention whether or not your images have been gilded.
Mercurial images are often quite dull before gilding especially if the mercury temp is too high.

New plates can be a problem.
Do you have any of your old plates to make a comparative test?

It is also possible that high humidity is responsible for the dullness especially if the time between exposure and developing is too long.

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Don’t add any water with the Cao. 200 grams of Cao is probably too much.
You don’t want Cao dust to get on the plates or it will make spots
If you have calcium hydroxide, heat it first to drive off the water before putting it into the fuming box.
The dish of slaked lime will cover too much of the halogen and must be removed before fuming to allow the halogen to contact the plates.
The color changes in the bromine are not very strong. The effect is most noticeable after the 2nd iodine fuming.
The silica gel will act as a dehumidifier also but may already have too much water in it.

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You slake calcium hydroxide by heating it to the melting point to drive off any water of hydration.
The slaked lime is then placed inside the box to remove water from the iodine crystals and silica gel too.
It does not adsorb the water on it’s surface like silica gel does.
It removes water by forming a hydrated salt.
It does not form any salt with pure iodine of bromine alone.
It will form a salt only if there is any hydroiodic (HI) or hydrobromic acid (HBr) in your box.
HI or HBr can form if Iodine or bromine are mixed with water when hydrogen sulfide is present

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Slaked lime like any deliquesent salt absorbs water until it liquifies, at which point it stops working but can be regenerated by heating to drive off all the moisture. Put it in as large a dish as will fit in your box and remove it when it is time to fumed a plate.
I suppose Dry Rite (calcium sulfate) would work too. Another possibility is a small pore size molecular sieve.
Molecular sieves are synthetic porous crystalline aluminosilicates which have been engineered to have a very strong affinity for specifically sized molecules. The definitive feature of the molecular sieve structure, as compared to other desiccant medias, is the uniformity of the pore size openings.

Number 3A molecular sieve, which has a 3 angstrom pore opening, allows polar water vapor adsorption (size 2.75Angstroms. whereas the non-polar bromine molecule is only 1.2 Angstroms so it doesn’t look like Br2 would be excluded.

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Correction: Fuming box depth quoted should be 80mm not 80cm.

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Andy,
If you consult Pobboravsky’s 1971 thesis posted in the resources area, you will note on page 40 that he broke up long fuming periods into as series of 60 second intervals with 60 second rest periods in between fuming to allow for the vapor levels to recover. I broke up my fuming box sampling by withdrawing a series of 50cc vapor samples with several minute intervals in between, during which I shook the vapor in the syringe with a solution of acid + sodium iodide to extract the bromine vapor from the air. In addition I ran the sampling tests in triplicate and got no more than a plus or minus 10% variation in results between samples.

Given the rapid speed of halogen molecules in the air, which increases with temperature, the vapor stratification should resume it’s equilibrium condition in a minute or less. The distance between the halogen solid or liquid and the plate, which was appox. 80 cm in Pobboravsky’s and my fuming boxes, would reduce the amount of stratification but not eliminate the effect.

The Clausius–Clapeyron equation can be used to relate the log (ln) of the vapor pressure of the halogen (or any other vapor) to to the log of the reciprocal temperature in degrees kelvin. (C +273). Plotting the log of the vapor pressures of bromine in the literature against the reciprocal temperature indicates that a +5C increase in temp approximately doubles the vapor pressure or vapor concentration.

The choice of using an 1840-1860 slide though fuming box design which offers minimal vapor loss and disturbance between opening and closings vs the more “modern” drop down lid type fuming box may be an important factor in deciding whether the operator is willing to live more vs less vapor disturbance during fuming.

Another possible variation may be the high humidity which often accompanies high temperatures in tropical regions. Bingtan makes no mention of this variable in his notes but most 19th Century operators report that water vapor is not desirable in fuming. Some suggest that water be removed by placing a dish of freshly slaked (melted) lime in the (iodine) box overnight. One might assume that silica gel does the same job here but eventually silica gel will become saturated with water which can not be remove without driving off the bromine at the same time. A dangerous and wasteful procedure given the cost of bromine to the Daguerreotypist.

[photolytic]

I use a bromine/lime mix that gives me a fuming time of 8 to 16 seconds at 20C

The vapor pressure of bromine at this temp (200 torr) should generate a vapor concentration of 1400ppm.

I took triplicate samples of the bromine vapor using a syringe equipped with a needle inserted through the pressure plate of the box where plate fuming takes place.

I converted the bromine to iodine within the syringe using an acidic solution of sodium iodide.
I did an iodometric titration analysis of these samples using sodium thiosulfate with starch indicator.

My results showed there was only a little over 1mg/l (1ppm) of bromine vapor at the top of the box.

I got even lower analyses (.01ppm) from my iodine fuming box where the vapor is even heavier.

Bromine vapor is heavy (2.5gm/cc) which probably allows for considerable vapor stratification in the box.

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[photolytic]

Are your fuming boxes kept at 35C also.
If they are the concentration of Iodine fumes at 35C is 3 times as high as it is at 20C.
Therefore your fuming times should be only one third as long.
The deep red color you see may not be in the first cycle of colors.
I suggest that you try examining the plate during the fuming to determine what cycle of colors you are using?
Generally the speed of the plate is lower if you fume past the first cycle of colors.

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Since you diluted your iodine in silica gel it is harder to measure (by weight) how much iodine you have left.
You could titrate a sample with thiosulfate solution using starch indicator to find out what is left.
However using the measurements of coating thickness published by Pobboravsky (1971 thesis) and a little chemical stoichiometry you can calculate that even after the heaviest fuming (400seconds), a 200nm coating of silver iodide on a wholeplate contains less than 25mg of iodine.
Therefore it is extremely unlikely that you have exhausted the iodine in your box. A low fuming temp (<20C) also seems equally unlikely given your location in the Philippines.
You don’t mention the brightness of the light on your subject but an exposure time of 30 sec @f2.8 is more typical for an iodized plate with no bromine. Perhaps you are low on bromine.
Also it is possible that you overexposed and underdeveloped your plate. You don’t mention the time over the mercury.

[photolytic]

Thanks for your input Mike.
Assuming that copper in the bath fogs the plates why doesn’t “galvanizing” by immersion, which plates silver on the front of the plate while dissolving an electrochemical equivalent of copper from the back of the plate, have a similar effect? Perhaps you have observed some fog when you “galvanize” by immersion. Let us know if you did.

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The entire experience was printed in the Members Favorite section of The Daguerreian Annual 2012 p235
For the benefit of non-members of the Society, I have included the text below:

Liam and Danny Boomker 4×5 inch Daguerreotype. July 11 2011.
Whether it’s a modern digital shot or a Daguerreotype, photographs of young children have always possessed a universal appeal. It was with this in mind that I set out to record the smiling faces of my two grandchildren on a Daguerreotype plate last summer.
I was confident that I could handle the squirming of two rambunctious children since I had the use of two high powered flash units, designed for high speed photography of sports events. More than enough light for Daguerreian portraits.
However I did not count of the unexpected skittishness of my younger grandson Liam to kick in just before the critical moment of exposure.
Liam, age 4 at the time, had been eager to participate since he always wants to do everything his older brother Danny, age 6 at that time, does and he knew Danny had been brave enough to face my Daguerreian lights last year when he had been the subject his portrait. Danny was confident and ready for his second experience under the lights, but Liam was not quite sure. A trail flash, to check the positioning of the slave trigger on the second light was all it took to set off the panic that followed.
Fortunately his mom, Amy Hurlock Boomker (p196 2001 Annual) stepped in with a maneuver often employed by determined mothers in the Daguerreian era.
A quick grasp of both his arms and Liam was temporally immobilized but still smiling broadly.
The resulting Dag, mom’s hands and all, has a charm few parents can resist.

The dag plate was not hyper-sensitized. The 9600ws was split between 2 Speedotron 105 flash heads, each positioned at 45 degree angles from the subjects, at a distance of 1.25 meters. Each head was powered by a separate 4800ws Speedotron 4803 power supply.

From my own experience, I can testify that after each flash the subjects eyes close involuntarily, but this is not recorded on the plate during the 1/250 sec flash duration. After the flash the subject sees a temporary blind spot in each eye for about 15 seconds but no long-term visual affect remains. I have not taken any flash Dags of any subjects older than myself and my wife, both about 70. However Danny was born with hypo-plastic left heart syndrome, which left him with no left ventricle. He underwent 3 open heart surgeries as an infant, and now at age 9 he has a nearly normal heart function.

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I have taken flash Dags using a 9600ws Speedotron 105 flash head at a distance of 1.25 meters using an f/2.8 lens.

The equivalent metric flash guide number (GN = Distance X f/n) is 3.5.

The Lighted or white camera technique used by S&H and probably learned from Mayall in 1845 can increase Dag speeds by about 33%. Exposure of Dag plates to other white light sources either before (hyper-sensitizing) or after camera exposure (latensifying) can double the speed of Dag plates. See the resources section for details.

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Any lamp of a neutral color will do. I use the light from a 40w incandescent bulb reflected from a sheet of white foam core from a distance of about 18 inches. Turn off any red safelight lamps in the darkroom as they will make the plate color look warmer than normal. (I.e. yellow appears rose).

If you are following up the iodine fume with bromine you must experiment with different times as the color does not change as much as the fuming time is increased. Keep the “bright” light on as you did with the iodine. The time may vary from as little as 4s up to 20s depending upon the strength of the bromine in the box.

After you reach the color you want, give the plate a 2nd iodine fuming approximately 1/3 as long as the first iodine fuming. Keep the “bright” light on during this fuming. Use longer fuming (i.e. 10, or 20s) if you want lower contrast. You may notice that the color changes more during this 2nd iodine fuming than it did during the previous bromine fuming.

At this time, turn off the “bright” light and use only a darkroom safelight. A 2s to 5s final iodine fuming is enough to get the plate ready for the camera exposure. Longer exposures will produce lower contrast images.

Camera exposure using indoor lights will depend of the color temp of the source but may be twice as long as for our sunlight exposures. See the Irving Pobboravsky exposure guide in the resources section

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Best to stick with the syringe transfer method for now.
I have no doubt that the mercury pours out in a straight stream.
The problem occurs when that stream hits the receiving container.
The resulting splash pattern is best depicted by Herald Edgerton’s electronic flash pictures.
Only mercury behaves like Edgerton’s splashed milk on steroids.
I presume you have wisely poured the Hg out of doors where any splashed mercury droplets can evaporate with minimum health hazard.

[photolytic]

Removing the screw-on mercury cup is a sound idea.
Removing the mercury with a syringe has its drawbacks too.
Mercury has a low surface tension plus a high specific gravity so it tends to splash rather easily when transferred from one container to another. (See Ken Nelson’s comments on this).
Removing all residual mercury from the syringe, especially the type with a needle attached, can also be difficult.
Perhaps you could design a screw in cap for the mercury chamber inside the developing box.
Attach it to the wall of the box with a small chain, like the gas cap on you cars fuel tank inlet, so you would not have to take it out of the box during developing
Keep up the good work Alan

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Daguerre himself originally used sodium chloride fixer before thiosulfate came along.

Ammonium thiosulfate or rapid fixer is also a very good alternative.

The other components in Kodak fixer are there to harden the silver gelatin image and are not helpful for Dags.

 

 

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Thanks Mike – Excellent post!

Back to Bruno.

I assume from your mention of a vacuum pump that you are using vacuum cold mercury developement. 

Your feed back is important. How is that working for you?

What vacuum, temperature and times work best for you?

Do you vent the fumes from your vacuum pump outdoors? 

Are you planning to attend the Daguerreian Society meeting in France in October?

 

 

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Gilding too long or at too high a temperature can cause a white fog or mist to form.

Uneven temperature or partial evaporation of the gilding solution from areas of the plate may cause wavy lines.

Careful leveling of the plate will help prevent the gilding solution from drying on parts of the plate.

Stop heating when you first see the white water vapor fumes on the surface of the plate. A strong directional light is helpful here.

The maximum temperature should be no higher than 60C. An infrared thermometer is helpful to measure this temperature.

Gilding for 3 to 5 minutes should be long enough.  Fog will form if you gild more than 8 to 10 minutes.

 

 

 

Happy gilding

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Jason,

Probably under development.

Due to the recent cold weather the top to bottom temp gradient in your mercury box may greater than usual.

Your rather long first iodine time (70s) also suggests that a lower temp in your darkroom may be the root cause.

I assume the 70degree was measured in the mercury itself whereas the temp on the plate surface may be considerably lower.

Remedy: When this happens, try increasing your developing time and or mercury box temp slightly.

[photolytic]

http://www.thaisilks.com/product_info.php?cPath=1_9&products_id=90

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EQUIVALENT MERCURY PARTIAL PRESSURES vs. TEMPERATURE AND PRESSURE
 

TEMPERATURE
CELSIUS

Mercury
Vapor
Pressure
as mm Hg

Partial
Pressure
@760mm Hg

Partial
Pressure
@150mm Hg

Partial
Pressure
@25mm Hg

30

.0028

.0000037

.0000184

.0001119

50

.0127

.0000167

.0000844

.0005068

80

.0888

.0001168

.0005920

 

 
 
 
 
 
 
 
 
 
 
 
 
 
A liter of air contains 1/22.4 or approx. 0.045 moles of nitrogen and oxygen.
At 80C the partial pressure of mercury vapor under atmospheric pressure is approx 0.089 mmHg/760 or 0.117 millibars.
The partial pressure of mercury vapor is equal to the mole fraction of mercury atoms in the air times the total pressure:     

 pHg = (Total Pressure)x    (Moles of Hg)

                          (Moles of Ox + Nit + Hg)

This corresponds to a concentration of 0.0000053 moles/liter of mercury or approx 1.1 mg of mercury vapor/liter.

It would appear from this that the 2-3mg of mercury in a CFl bulb is more than sufficient to develop at Dag even in a mercury box with a volume of 2 to 3 liters.

However, as jgmotamedi has so wisely pointed out, this is not the whole story. Unless you have a very large number of burned out CFL bulbs, the cost of new bulbs would make them a very expensive source of mercury for the Daguerreotype process.

The CFL bulb also contains a larger quantity of phosphors which would quite likely interfere with the Dag developing process.  

Stick with old mercury switches or thermometers.

 
 
 
 
 
 
 
 
 

[photolytic]

Lippmann plate of fruitbowl made by Darran Green on 14/07/2002.

Reflected vs transmitted light.

Collection of David Burder

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[photolytic]

Lippmann plate of fruitbowl made by Darran Green on 14/07/2002.

Collection of David Burder

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[photolytic]

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