This weekends failure

[botticelli1972]

This weekend I gave it a go at a vacuum cold mercury dag a la John Hurlock. Well long story short I got nada. I did a test exposure with a 1 min. graduated scale over the plate in full sun at F2.8 so exposure should not be the issue. I think my problem was in the iodine step (I only did single sensitizing as I have yet to get up and running on bromine). I am used to getting a deep yellow with Becquerel and I fear that I left the plate in too long. Some of John’s writings state that he only goes over Iodine for 15-40 seconds. I usually use 2-3 min. I have to admit that I looked at it after 30 seconds and didn’t see a thing but I guess I could be looking for the wrong thing. Those of you who do mercury, how long do you leave it over the iodine? I have a 5 x 7 Pyrex with a thin layer of crystals covering the bottom. The plate is about 2 to 3 inches over the crystals I would guess.

Also I was not sure how much mercury was necessary I put a quarter sized bead of it in the bottom and pulled a 27 1/2 inch vacuum, should have been enough for a 3 hour development. I checked on it ever few hours and nothing, in the end I left it in 18 hours over night. As a side experiment I put it under amberlith in the window before I left the house this morning, ill report the results tomorrow. -Larry

[photolytic]

Hi Larry,

It sounds like you had a rather frustrating experience.
It actually took me 6 or 7 experiments before I had success with it but then I had no one to tell me if it worked at all.
Your exposure sounds long enough but your fuming might have been too long.
Not only does a thicker coating slow down the plate a bit but it hides the developing image until the Dag is fixed.
If you had fixed your Dag you might have seen an image.
The best way to see the developing image in the vacuum chamber is to shine a red light at a low angle across the surface of the plate. I use a rubylith filter on my flashlight but a red or yellow LED would work well also

You don’t mention the type vacuum apparatus you used or the temperature.
The plastic vacuum desiccators that I originally used did not hold vacuum well enough so I would recommend using glass apparatus. For best results the vacuum must remain at or above 23 inches of mercury and the temperature above 15C during the developing process. If you are in doubt whether you have a vacuum leak, you can leave your vacuum gage attached to the vacuum chamber and check it just before opening the desiccator.

During fuming, you should "take a look" at the plate during the coating process to monitor the progress. So long as you finish off the fuming process with a final exposure to iodine fumes in the dark or under a safelight this light exposure will not fog the plate. This light exposure should not be confused with flashing or hyper sensitizing the plates with light after all fuming is complete.

If you have read Susan Barger’s book or my second article "The light after the Bromine" in the resources section of this forum, you will see that weak light exposure, particularly during bromine fuming, actually increases the speed of the plates. This In-process light breaks down some of the silver halide on the plate into atoms of metallic silver which Barger calls Photolytic silver. These photolytic silver atoms combine with the latent image of the Dag forming a stronger image.

Good Luck, John

[botticelli1972]

Thanks for the response John. I have read all your articles many times and have been wanting to try the method since I was able to see your work in Kansas City last year.

I checked and fixed the plate last night to see if anything did happen. First of all the amberlith exposure I tried did nothing as far as pulling an image out. But after fixing I did see "something". It was not an image but a I could tell where the plate was masked by the holder during exposure and that an effect had occurred. Also, there were a lot of very tiny balls of mercury on the surface, I would imagine that was caused by leaving it in for 18 hours under vacuum. I assume this is the same as when left in the heated apparatus too long. The mercury balls did not appear attached as they would roll around on the surface in the fixer.

For my set up I do have one of the plastic vacuum desiccators with a very old scientific pump that has a pulley and a separate motor. The vacuum gauge is attached to the pump, but I did do a test last night and it held 27" of vacuum for 4 hours with out a drop in vacuum. When I get a chance Ill get some more plumbing and set the gauge inline for more accurate readings.

In order to get light exposure during bromine fuming is it possible to use a clear glass/plexi bromine box? or is it best to expose it to light after the bromine step and before the final iodine? I am still a ways off from bromine and I was planning on building new sensitizing boxes, mine are from when I first started and are a poor design, I have learned much in the last few years.

One other thing, is it necessary to burn off the mercury before re-polishing? I was thinking it might interfere with the process or is it just not necessary and will be eliminated with polishing?

Larry

[photolytic]

Larry,

Also, there were a lot of very tiny balls of mercury on the surface; I would imagine that was caused by leaving it in for 18 hours under vacuum. I assume this is the same as when left in the heated apparatus too long. The mercury balls did not appear attached as they would roll around on the surface in the fixer

Be careful not to let these settle on the plate surface or they with form a large white amalgam spot which requires more buffing to remove. If not completely removed they will leave a dark spot on the next image.

For my set up I do have one of the plastic vacuum desiccators with a very old scientific pump that has a pulley and a separate motor. The vacuum gauge is attached to the pump, but I did do a test last night and it held 27" of vacuum for 4 hours with out a drop in vacuum. When I get a chance Ill get some more plumbing and set the gauge inline for more accurate readings.

I assume that you turned the pump off during the 4 hour interval

In order to get light exposure during bromine fuming is it possible to use a clear glass/plexi bromine box? or is it best to expose it to light after the bromine step and before the final iodine? I am still a ways off from bromine and I was planning on building new sensitizing boxes, mine are from when I first started and are a poor design, I have learned much in the last few years.

We’re talking brief exposure to low levels of 40w incandescent light here,
It is best to use an ordinary opaque wooden box and expose the plate for 5-10 seconds at a time during the color inspection period of the fuming process.

Is it necessary to burn off the mercury before re-polishing? I was thinking it might interfere with the process or is it just not necessary and will be eliminated with polishing?

Not unless you get mercury amalgam spots from those balls of mercury.
Just wipe the image away with a soft tissue and buff the plate in your usual way.
If you see any ghost images from the previous use before or during the next fuming step repeat the buffing procedure. Generally speaking it takes more rigorous buffing to restore a used plate then it does to buff a virgin plate, assuming the new plate had a smooth surface to begin with.
If you do decide to "burn" the plate be sure to wipe the image off with a tissue first.
Burning the plate hardens the image, making it more resistant to removal.

Good luck,
John

[Author]

Posts