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Ray Rogers
04-24-2008, 10:03 PM
I do not recall any direct mention of this being used to produce black and white images
having contrast differences.

I have now found the information, so the above comments are no longer valid.
It is, however, still much later than the material I initailly hinted at... and so the search continues for the rest of the story.

Thanks for pushing my buttons and making me go through my files!

Since it is too late to get much sleep now, I am off to pick up a new arm and leg... uh, i mean electrodes. They are sure expensive enough! (up til now I have been reading the analog needle type under red safelight - you know where you line up the shiny part with its shadow... not an easy task in a darklab!
Anyway, next comes automation... so this newer digital work horse will be worth it... I hope.

Unfortunately, my ions are still metered analogistically
tosleepieetotalk....

AgX
04-25-2008, 04:07 AM
PE, Ryuji thank you both so much for those informations!

I was aware of the technical shortcomings of the industry of that time.

Well, I admit blending emulsions was not a good idea, due to the inherent blue absobtion, which would needed a kind of desensitation of one. But my other idea was that they could have made two emulsions yielding different gammas, give one an ortho sensitation. Coat the unsensitized, coat a filter layer (which should discolour while processing…) coat the ortho emulsion. Yes, quite a hazzle.
And I totally forgot about any migration of filter dyes and about the remaining colour of the sensitizer dyes….


Ryuji,
I was in the belief that sensitzers had a great adsorbtivity to the halide (keeping aside that problem of substitution by an anti-fogging agent you referred to elsewhere). Thus they won’t migrate. If they would migrate later whilst processing that should not be a problem (in contrast to those colour couplers).
A problem however would have been if the migrated while coating. But wet/wet coating was not done anyway then.
Thus there might still be a migration, whilst in stock, of not adsorbed sensitizers still around in the gelatin.
Was it the latter you were referring to?

Ryuji
04-25-2008, 07:13 AM
Adsorption of dye molecules on AgX surface varies a lot depending on the dye. (And this is also true of developing agents, etc.) Good ones adsorb quite well. But I am not sure (without doing a bit of research) if good ones were in common use, or at least available in commercial quantity c. 1912.

Another reason why variable contrast emulsion was not very good until 1970s (at least) has probably because it is not very easy to make a high contrast emulsion using single jet method (which was described by AGFA people in 1950s, but it remained only within the research community for another decade or two) and the methods of variable contrast emulsion can only lower the contrast, not boost, beyond the effect you would get from a larger coating weight of one of the emulsions. Now we can make monodisperse emulsion using double jet, and a single emulsion (without any special development technique) can be made fairly high contrast. So it makes more sense to start with these and vary the contrast by lowering it.

Photo Engineer
04-25-2008, 10:10 AM
AgX;

I have mentioned elsewhere that I have, within my reach, the ability to make a variable contrast Azo type paper. It uses all of the methods I've mentioned here, including the base soluable sensitizing dye which I have a supply of. It is doable because the Azo type emulsion, which is single jet, can be made in contrast grades from about 1 - 4. This is also doable with the AgBr enlarging emulsion that I posted earlier, although I have not done significant work on it yet.

It is also the reason I have been working on 2 layer coating with my blades so that I can have an alternalte method of doing this if blending does not work. Of course, the dual coating is also intended for color work sometime in the future.

I am in doubts as to whether I should proceed though as there did not seem much interest in VC contact paper, and VC enlarging papers are still available. So, right now a lot of other things are undergoing development and these projects (including color) are on the back burner.

I should also add that I have never seen a modern tinted VC enlarging paper. This indicates that there is no significant blue absorbing dye, and no huge level of sensitizing dye to discolor the paper. Much of this is achieved by using a super-sensitizer, which is not a dye, but a colorless additive which boosts dye sensitivity manyfold. Therefore, VC papers are white. This also indicates that the silver halide is high in chloride and low in bromide and iodide which impart a yellowish cast to the raw paper. Of course, the low silver level in modern papers will repress any visual impact of color as well.

PE

Kirk Keyes
04-25-2008, 12:57 PM
Ray - what kind of electrodes are you getting? I've recently bought a digital pH/mV meter and a pH electrode as well. What are you using?

Ray Rogers
04-25-2008, 02:40 PM
Ray - what kind of electrodes are you getting? I've recently bought a digital pH/mV meter and a pH electrode as well. What are you using?

They are 3 seperate type electrodes, not 2or3 in one.
pH range 0-14
0-100 degree C.
that require a minimimum of 20 mL

Now I am starting to have second thoughts...I wonder if I should have tried something new this time... I don't know... I did pick them up today, but I find I'm still looking at design specs for other models.... Monday I will be hearing from the mfg. anyway maybe I will exchange it...
there are +es and -es to either choice.

How about yours?

Ray

Kirk Keyes
04-25-2008, 04:21 PM
Ray -

From my lab experience with everything from very clean waters to really scuzzy samples, I highly recommend Thermo/Orion Ross-type electrodes. They seem to last a long time and are pretty stable. Much more than regular old fashioned general use electrodes I've used in the past. I see Ryuji suggests using Ross electrodes on his web site as well. The Orion 81-02 electrode should be a good one.

Here's a nice guide to Orion Ross electrodes:
http://www.boekel.ca/catalog/en/ph_electrodes_orion2.html

That said, as I wanted to stay somewhat on budget, I bought a Mettler INLAB 413 pH triode electrode with a built-in temp probe. Unfortunately, the connector on the Mettler temp does not mate with my Orion meter... But it was only $40 and new in box.

I see right now there is an Orion Ross electrode on ebay:
http://cgi.ebay.com/NEW-THERMO-ORION-ROSS-COMBINATION-PH-PROBE-8104BN-BNC_W0QQitemZ180235960752QQihZ008QQcategoryZ26230Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

Watch out as there is a Ross half-cell and for sale as well, and the person selling the above linked electrode also has an electrode that says Ross in the title, but it is not if you look at the listing... it's an Orion perPhect pH electrode with has an Ag/AgCl junction, not the best for photographic uses, but a good overall electrode for other uses.

Something like this would be a good choice. It's a "heavy duty" model, which one may want if they are not used to handling pH electrodes, or if they are clumbsy...

For people reading this that are looking for bargains, absolutely do not waste your time with a used lab elctrode. All the labs I've been in, when an electrode is going bad or getting old and response is sluggish, they disconnect the electrode, and set it on the counter behind the pH meter. And then is sits there, sometimes for a long time, getting dry and crusty. And not good to use after that. And then there's the ones that have cracks in the sensing bulb. Buy something new when getting a pH electrode.

Also, make sure you get one that is a "combination" electrode. Not a "half-cell" electrode. You want a combination as it has the half-cell reference electrode build into the body of the pH electrode - so it's really two electrode in one housing. You want that. Also, if you can get a temp probe built-in as well, that's really nice. Those electrodes usually have "triode" in the name to let you know that it's got pH, half-cell reference, and temp all in one unit.

What have you been using and what are your looking at?

Photo Engineer
04-25-2008, 04:32 PM
Ray, Kirk;

I suggest looking here:

http://hannainst.com/usa/subcat.cfm?id=002&gclid=CPSsjpGH95ICFQKAHgodmmGNxQ

You used mine in the workshop Kirk.

PE

Kirk Keyes
04-26-2008, 12:35 AM
Yeah, it's a nice meter and certainly friendly to the budget, but sometimes it's nice to have something that is more versatile.

Ray Rogers
04-28-2008, 06:20 AM
Ray -

...there is a Ross half-cell and for sale as well, and the person selling the above linked electrode also has an electrode that says Ross in the title, but it is not if you look at the listing... it's an Orion perPhect pH electrode with has an Ag/AgCl junction, not the best for photographic uses, but a good overall electrode for other uses.

Kirk,

Since the Ross reference is said to be neither Ag nor Hg based, what is it?

Ray

Kirk Keyes
04-28-2008, 11:50 AM
Ray - good question... I don't really know. But the advantage of the Ross design is it's quick response to temperature changes. In the labs I work in, we are calibrating at room temp and then measuring samples that are usually refrigerated, so they are 4-10C. The Ross electrodes give really quick response when switching back and forth from solution to solution. The lack of silver and mercury is an added benefit for our use in photographic applications.

Photo Engineer
04-28-2008, 12:01 PM
You know that two silver electrodes on a multimeter will work, but you have to convert the voltage readings into vAg by doing laborious calculations so that you have a conversion table. So, an off the shelf Radio Shack VOM should work. I have not tried this myself, but a friend has and said it works fine except for the initial calibration and that requires the conversion table preparation.

PE

rmazzullo
04-28-2008, 12:56 PM
Hello PE,

Do you know where we can find those calculations? It should be possible to input the voltage readings in to a handheld or a laptop and write a small program to make the calculations on the fly, and in so doing, enable us to use more readily available electrodes....

It may not be the cheapest route, but it could be used as part of a process control setup.

Bob M.

Photo Engineer
04-28-2008, 01:06 PM
It must be done from the Nernst equation and the Debye-Huckle equation. You would enter salt concentration and get out the vAg or pAg. Then you compare that to the voltage or resistance on the VOM. Then you plot the voltage against vAg to get a conversion chart. Once the chart is done, you only need it and the VOM apparently. I have not tried it, as I said, but a friend has. Further than that, I can't say until I try it. I have no reason to dobut that it works, and it really should but it would not be as accurate as the system we used at Kodak.

PE

Kirk Keyes
04-28-2008, 01:59 PM
It should be possible to input the voltage readings in to a handheld or a laptop and write a small program to make the calculations on the fly, and in so doing, enable us to use more readily available electrodes....

Bob - I don't think you'll find electrodes that are any more available than ones designed for pH type meters. Electrodes are usually avail with BNC (sometimes called "British Naval Connector", but are actually termed "Bayonette Neil-Concelman") fittings and these will fit nearly any pH meter you can buy made in the last 20 or so years. If you want to use an older meter, you can get BNC adaptors to fit those too.

Also, a lot of these pH meters come with serial connectors, so if you're going to all the effort to input measurements from an electrode into a computer, then running the electrode into the meter and then importing the serial output into a computer will be the quickest and easist way to get this done.

Kirk Keyes
04-28-2008, 02:02 PM
It must be done from the Nernst equation and the Debye-Huckle equation. You would enter salt concentration and get out the vAg or pAg. Then you compare that to the voltage or resistance on the VOM. Then you plot the voltage against vAg to get a conversion chart. Once the chart is done, you only need it and the VOM apparently.

This is what a pH meter does... Save yourself some time, unless you REALLY like to DIY it.

And remember, nearly all pH meters also will give results in mV (millivolts) if you can to see the direct output from the electrode. Or if you are using like a redox electrode, you would actually use it in mV mode.

Photo Engineer
04-28-2008, 02:19 PM
Of course Kirk, but most pH meters do not have two silver electrodes, and some do not read in mV. I think, according to my friend, that the glass/silver combination will introduce a bigger bias in the scale. Not sure, as I repeat that I have not personally tried this.

At Kodak we used a very different method to prevent salt contamination and calomel contamination, as well as having a special silver electrode.

PE

Kirk Keyes
04-28-2008, 04:08 PM
Ray - with all the talk about patents around here, maybe this one will answer it...

http://www.google.com/patents?id=w7AuAAAAEBAJ&dq=ininventor:ross+inassignee:orion&as_drrb_ap=q&as_minm_ap=1&as_miny_ap=2008&as_maxm_ap=1&as_maxy_ap=2008&as_drrb_is=q&as_minm_is=1&as_miny_is=2008&as_maxm_is=1&as_maxy_is=2008

Ray Rogers
04-29-2008, 04:55 AM
Ray - with all the talk about patents around here, maybe this one will answer it...


Unfortunately, it doesn't.
Unless I am totally snowblind...

I imagine it IS in one of those patents, just not this one.

Perhaps this is an example of what PE was saying about one real "invention" (my words) or product, being spread out over several "patents"... who knows, but anyhow, this particular patent does not seem to describe the "Ross" reference system.

Ray

Ray Rogers
04-29-2008, 05:24 AM
Ray - good question... I don't really know. But the advantage of the Ross design is it's quick response to temperature changes.

I read the Owners manual... The fact that they say you have to insulate the sample from the stirrer with styrofoam(?) sort of bothers me...

While I DO wonder if it is really so sensitive (do you insulate like this in your own professional work?), either way, in some situations, high sensitivity could be another way of saying "less robust"....

I have not made a final decesion yet, but at this point, the Ross line sounds more like a Chiwawa than a German Shepherd to me!

I am more of a Collie man myself.