[Pobboravsky]

The graph in Figure 3 comes from Study of Iodized Daguerreotype Plates. It shows the absorption coefficient of silver iodide versus wavelength. Wavelengths from 350 to about 400 nanometers (nm)correspond to UV radiation. Wavelengths from about 400 to 450nm are seen as blue light. Only wavelengths that are absorbed by silver iodide can produce a photochemical reaction — i.e., can contribute to exposure of an iodized plate.

Since lenses generally block most, if not all, UV radiation, only blue light can expose iodized plates.

The graph shows that the absorption curve goes to zero for wavelengths greater than 450nm meaning that the plate is not sensitive to green and red light. The UV absorption (read, sensitivity) rises from 400 to 350nm.

[Pobboravsky]

Thanks Alan,

My guess would have been that most of the UV would be stopped by the lens but that some small fraction would get through to the plate.

What is the highest UV Index you have measured in the past?

Quote from Mike Robinson:

I once did a workshop at the Amon Carter Museum in Texas and the only lighting we had available were UV bulbs (those horrible blacklight bulbs that were used for POP printing and the like). The exposures were comparable to my north light daylight, BUT the skin tones were very unflattering.

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I wonder if the UV bulbs he used gave off blue and violet light as well as UV. And that is why he got comparable exposures to north skylight. The mystery remains.

Again, thank you for your help.

Irv

[Pobboravsky]

Alan: what were the reading(s) without the lens or glass? Irv

[Pobboravsky]

Hi Alan,

Could you please measure the UV Index through a lens and again with the lens removed? The lens need not be on a camera.

And could you also do the same using two pieces of window glass instead of a lens?

What a powerful website this is for gathering information from a wide daguerreian audience! Mike Robinson said he made daguerreotypes using UV lights for portraits and the exposure time was about the same as with north light illumination. Now, I will not say this publicly, but Mike is a very clever fellow. But, I assume he used a lens.

Kudos to you, Jon, Andy and the daguerreian community.

Irv

[Pobboravsky]

Hi John –

Let me quote me when I saw your sunflower d-type. “Ooh, wow”. Nice going.

Irv

[Pobboravsky]

Hi all,

Re: viewing color of iodized plate (Becq): You can safely view the color under normal room light and when you get the desired color, switch off the light and switch on a yellow safelight (like a 15- or 25-watt yellow bug lamp) — then re-iodize the plate for 2-3 seconds. The yellow safelight allows you to see to load the plate into a holder.

Why does this work? While inspecting the color of the coating under bright room light, the light is producing a uniform latent “image” over the entire plate. This latent image consists of sub-microscopic groups of silver atoms. Re-iodizing converts these silver atoms to silver iodide wiping out the latent image.

Another use of re-iodizing: Let’s say a child being daguerreotyped cannot hold still during an exposure, a few seconds re-iodizing allows you to erase the latent image and re-use the plate.

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During I-Br sensitizing the coating can be viewed under bright room light after the first iodizing stage and also after the bromine stage. The last step, second iodizing, is done under safelight conditions. Second iodizing erases the latent image produced during the first two sensitizing steps.

Irv

[Pobboravsky]

M. Bailun,

With the incident meter set at ISO 100, EV=14, f/2.8, outdoors — a first cycle exposure time would be about 20 seconds. Based on your experience, does this seem to agree with your results? Other workers: please let us know if this seems about right?

In my 1970 work I found that a first-cycle yellow is more sensitive than a second-cycle yellow. However, the image made with a 2nd-cycle yellow is much less contrasty than that of a 1st-cycle yellow. A 1st cycle yellow plate because of its very high contrast must be used with flat lighting – like on an overcast day. On a bright sunny day the shadows will come out dark and without detail – assuming the plate is exposed to get correct highlights.

A 2nd-cycle yellow plate does a better job of recording information in the highlights and the shadows. You need not be limited to shooting on an overcast day. But it is not as fast as a first-cycle plate.

What Meegan found is that the effective speed of a 2nd cycle plate can be increased by increasing the Becq. development time to hours instead of the 20 minutes used in my 1970 experiments. Increasing Becq. development time to hours also had the benefit of producing neutral tones instead of the bluish tones obtained with shorter dev’g times. He also experimented with dev’g times of 24 to 48 hours and with cycles greater than 2. I have seen some of his images and they look similar to ones dev’d with mercury.

By increasing the total light energy used in extended development — it compensates for “underexposing” the plate in the camera.

Does any of this make sense?

Irv

Gerry Meegan found that he could

[Pobboravsky]

M. Bailun,

The last Becq. d-type I made was probably in 1970. I have enough trouble making mercury-developed d-types. I am not interested in making Becq d-types. 3rd cycle yellow plates tend to fog. Jon’s 3rd cycle images are not fogged. This means he knows how to make such images which is more than I know.

Since I have never made a successful image on such a plate I have no idea if Gerald Meegan’s short exposure time is correct. I know he is a veryclever man who has made some very interesting observations.

I do not know how to predict the speed of a 3rd cycle plate based on the speed of a first cycle plate.

M. Irv

[Pobboravsky]

Hi Jon et al Becquerellers

I would find it even more useful if the the (exposure)lighting type could be included in the description.

By lighting type I mean daylight, north light, tungsten, photoflood, fluorescent, and so on.

The effective speed of the plate depends on the blue content of the light.

Imagine a subject illuminated by north light which has lots of blue light. Now, imagine the same subject illuminated by a 100-watt tungsten light which has far less blue light. Imagine also that the meter gives identical EV readings for these two light sources. Since the EV is identical it might seem reasonable to give identical exposures. However, if the north light image is correctly exposed, the image with the tungsten light will be grossly underexposed.

Why is this so? Light meters respond to the entire visible spectrum; an iodized plate responds only to the blue light getting through the lens. UV radiation is absorbed by the lens.

I wonder if the exposure discrepancy in 3rd cycle yellow plates between Monsieur Bailun and Monsieur Meegan might be due the difference in the blue-light quality used by M.Bailun.

Monsieur Irv

[Pobboravsky]

How to calculate bellows exposure factor:

1. Divide the bellows extension by the focal length of the lens.

2. multiply the above result by itself.

This gives the bellows factor. Multiply this bellows factor by the exposure time given by your light meter to get the corrected exposure time.

An example.

bellows extension = 14

Focal length = 7

(1) 14 / 7 = 2

(2) 2 x 2 = 4

[Pobboravsky]

Hi Andy,

How was the reference plate prepared? How did your plate preparation differ?

Irv

[Pobboravsky]

I have been thinking about Andy’s question of how to tell when to change to a fresh abrasive paper on a random orbital sander. When you begin to wonder if it is time to change the paper shift the r.o.s. so it is only polishing half of the plate for a given period of time, say 2 or 3 minutes. Then compare the two halves to see if the extra polishing made any difference.

Adding a few drops of water to the plate when polishing with 3M wet-n-dry polishing papers increases the polishing rate.

Irv

[Pobboravsky]

This is Irv Pobboravsky with some questions for emf.

Quote:

“I start with 2000 grit wet/dry sandpaper on a sheet of glass to try to flatten the copper and get rid of the orange-peel.”

1. Does the 2000 wet/dry sandpaper remove the orange-peel?

2. How thick are your plates? Could you expand on what is meant by “flatten the copper”

3. What holder do use for the 2000-grit? (backing?)

4. Do use the sandpaper with water?

Irv

[Pobboravsky]

The Masochist’s Delight copper prepping method was done in Feb 2006. Today I tried it again, this time with an unusable electroplated plate which had silver blisters. The aim was to remove the silver layer down to the copper and to remove the orange peel on the copper. This reminded me of repressed memories worth sharing.

This 5×7 inch plate was 20-mils (0.5 mm) thick and it became convex in the 7-inch dimension after ROS sanding with 320-grit sandpaper.

(1) To keep the plate flat one should (ROS)sandpaper the back first and then work on the front.

(2) To minimize the dust generated by 320-grit sanding, use a sandpaper disc with its holes aligned with the holes in the backing plate. The dust will be vacuumed up by the sander as it operates and will be collected in the bag that fits on the back of the sander. (Now that I’ve told you about it I will use it next time).

(3) The 320-grit sandpaper produces a coarse matte surface making it hard to tell when the orange peel surface is removed. After a few trials you will find how long to run the sander for complete orange peel removal for your set of conditions (plate size, etc.) Residual orange peel will show up as the matte surface become finer after one of finer micron steps.

(4) My guess is that the 1-micron Polishing Paper is not needed. After the 3-micron step the copper will have a very fine matte surface and will be ready for silver plating. It isn’t necessary for the copper to be shiny.

[Pobboravsky]

If the Cu-prepping method you use ends up giving final images with which you are happy, use that method. Going beyond that is a waste of time, money and effort.

Beginning daguerreotypists are faced with many problems — a perfect copper surface may be the least of the problems. I think getting a handle on sensitizing, exposure and development should precede the effort of getting a perfect copper surface.

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Removing deep scratches Conjecture: I wonder if step 1. (ROS with 320-grit sandpaper)followed by wheel polishing might be shortest path to enlightenment. I haven’t tried it.

[Pobboravsky]

Hi Andy,

1. The copper (Cu) is adhered to plate glass (~12×14-inch) with four ~half-inch pieces of double sided tape. Some of the Trizact steps produce a slurry which spreads beyond the (Cu) onto the plate glass and would contaminate the next polishing step if it were not removed. The (Cu) is detached from the glass by sliding an artist’s palette knife under it and giving the knife handle a slight twist and then the Cu is rinsed under running water – front and back. The glass is then cleaned and wiped dry. All the steps are time-consuming and I welcome ideas that would shorten the time. A Masochist’s Delight is descriptive of the method as it now stands. The final surface quality is the best I’ve been able to achieve but getting there is not half the fun.

2. I mount each Trizact grade onto a separate foam disc because Trizact lasts for a bunch of plates. Peeling off the psa backed Trizact and replacing it with the next finer grade adds extra steps. The polishing papers last for doing barely one 5×7 and they must be replaced. The abrasive slurry produced during the Trizact steps would get onto the backing plate which would then need to be cleaned; mounting them on separate foam discs keeps the backing plate clean. Although I haven’t done it, a separate plate glass for each abrasive grade would reduce the amount of cleaning needed. Doing a series of Cu plates with, say the 30-micron Trizact, and then switching to the 10-micron grade to do the next step might reduce the time.

There is lots of room for improvement.

[Pobboravsky]

Polishing Copper –A Masochist’s Delight

The number of polishing steps depends upon the surface quality of the copper with which you start and what you want in the way of a final surface quality. Even so-called “mirror finish copper” has an orange-peel surface. Silver electroplating will faithfully retain all the surface defects of the underlying copper substrate.

The steps below assume you are starting with very poor surface quality copper.

1. 320 grit (or 600 grit) abrasive paper attached directly to Bosch random orbital 5”-diam. backing plate (foam disc not used). Speed 1 – Try 1 to 2 minutes (I neglected to record duration.)

2. 30-micron 3M Trizact (green), pressure sensitive adhesive (psa) on 5-inch diam. foam disc. Water added from time-to-time with eye-dropper. Approx. 5 min for 5×7 inch plate.

3. 10-micron 3M Trizact (blue), psa on foam disc plus water as above; for about 5 min.

4. 5-micron 3M Trizact (orange), psa on foam disc plus water as above, ~ 4 min.

5. 3-micron 3M Polishing Paper w/ a few drops of water. 4 min. 3M adhesive sprayed onto back of pol’g paper and pol’g paper adhered to foam disc, overhang scissored off. 4 min.

6. 1-micron 3M Pol’g Paper as above.

In the interest of eliminating the first step in the list you may decide not to remove the orange-peel surface. (Some masochists have their limits.) However, if you start with deep surface scratches you will likely choose to eliminate them by doing the first step.

I don’t pretend to know if the final steps are really needed. Experience will guide you. Silver is far easier to polish than copper so you may decide not to do the last two steps.

Plates smaller than 5×7 require less time. Initial cost of Trizact is higher than conventional abrasive materials but it lasts and lasts.

This method can produce a surface free of scratches and orange peel. Consider this method in need of modification – it is just a jumping off point.

[Pobboravsky]

Hi,

Methinks 3M is missing out by not having a Daguerreian Division. It really takes patience and persistence to crack their barriers; kudos and admiration go out to you Andy.

Using remnants of 3M polishing papers: I have found that two pieces (3.5 x 5 in.) of the remnants can be adhered to the Bosch foam disc and the overhang scissored off. This means you can get three 5-inch diameter discs from a 8.5 x ll inch sheet instead of just two. Works out fine.

Irv

[Pobboravsky]

The 3M web site doesn’t work.

If at first you don’t succeed…

3M Polishing Paper Link

I hope this one works. If it doesn’t,search Google using search phrase: 3M micron polishing paper and click on the 3M website.

Irv

[Pobboravsky]

Hi Race and Andy

Plumber’s Supply is new to me. Their price for a “Sponge Applicator Pad is nearly half of what I just paid at another source. Thanks Andy.

3-M polishing papers:

For more information on 3M™ Wetordry™ Polishing Paper

contact your local 3M Distributor or call 3M at 1-800-742-9546.

http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs666Ho5COrrrrQ

I use 3M Spray Mount Artist’s Adhesive, No 6065 to adhere a 5x5inch square of the 3M Polishing Paper to a Bosch Sponge Applicator Pad RS013. The back of the 3M pol’g paper is sprayed with No.6065 Adhesive and the paper is attached to the sponge pad. Overhanging pol’g paper is trimmed off with a scissors. The No. 6065 Adhesive allows repositioning so that when the a 3M pol’g paper is worn out, it can be easily peeled off the sponge pad and replaced with a fresh pol’g paper.

5″ diameter “Pressure sensitive” 3M Pol’g paper would be a better solution if a source could be found. The 3M website (above) shows photos of pol’g paper discs.

[Pobboravsky]

Hi Jon et. al.

Yes, chrome oxide is available in powder form.

http://cgi.ebay.com/Maimeri-Pure-Pigments-Chrome-Oxide-Green-Carbon-Black_W0QQitemZ310121957007QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item310121957007&_trksid=p3286.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

Keywords for search engines (supplies): lapidary, metallurgy, Baikowski(0.1 micron alumina polishing powder, agglomerate free), optical polishing media, artists pigments.

Good luck,

Irv

[Pobboravsky]

Hi Andy,

John is right – do not wash plate after the rouge, chrome oxide or lampblack polishing steps. After the last polishing step (lampblack) I suggest using a small handbuff (3-M sanding block covered with Ultrasuede) to remove any abrasive particles adhering to the plate surface. It takes less than a half minute.

The above abrasives are not appropriate for polishing copper. When I have time I will outline how I do that.

Silver polishing can take anywhere from 2 to 5 minutes per step depending on the surface quality of a given plate.

Good luck,

Irv

[Pobboravsky]

John, thanks for your kind thoughts and your questions. The 80% Polyester, 20% Polyamide material you mention is not Ultrasuede but a microfiber cleaning cloth.

Ultrasuede is 100% polyester ultra-microfiber non-woven with a non-fibrous polyurethane binder. Ultrasuede feels like chamois; in fact I bought “chamois” color so it even looks like chamois.

I’ve only used the thinner variety of one color so I cannot comment beyond that.

Polishing speed: I polish at the lowest speed which is speed 1 on my Bosch random orbital sander. I haven’t quantitatively compared the relative polishing rates of silk velvet and Ultrasuede but it seems to me that Ultrasuede polishes in a shorter period of time. Why? My guess is that Ultrasuede has the greater contact area (more abrasive per unit area). The contact area of velvet is less because it is made up of discrete fibers sticking up at right angles to the surface. I would guess that the rate of real chamois and Ultrasuede are the same because they have similar surfaces. This is conjecture on my part.

I use very minute dustings of chrome oxide powder (so-called green rouge) followed by lampblack on separate Ultrasuede-covered foam pads on my r.o. sander. I use 0.1 micron alumina powder on a silk-velvet covered foam pad with a drop or two of olive oil prior to the chrome oxide and lampblack.

Best regards,

Irv

[Author]

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