10 lessons in photography!

[Harold_4074]

CJ:



It certainly looks as if water is not the issue, and a 30-second emergence versus 30 minutes pretty well rules out temperature, because you would notice that kind of change just from touch. If I had to guess, I would say that your assumption of poor quality control on the part of Rockland is probably correct. If your five orders came from three batches (one good, two bad) it would be enough to explain what you are seeing. The flaw in this is that you would need some way to verify that the plate batches weren't bad (hence the idea of "control strips" from one batch to the next).

I have no experience with the Rockland materials, but I have a hunch that their developer is one of the so-called "physical development" formulas, which plate silver from the developer onto the image as it develops. If so, you might find a suitable formula on the Web or in the Anchell book. Using a conventional developer followed by an intensifier might also work.

If I have any more inspiration, I'll email you directly; I doubt that many people find this sort of problem as fascinating as I do!

[Paul Butzi]

I did notice that the older (and drier) the plates, the faster the emulsion is (by 2 to 3 stops). Given that the Rockland tintype chemistry only has a useable range of about 1 stop, that means a LOT of wasted material trying to figure out what exposure to use.

I wonder if a good way to use minimal material to narrow in the speed at any point would be to make a contact print of a Stouffer 31 step step wedge onto a plate, then develop it. If you always used a known exposure for the contact print, you should be able to get the 'film' speed within 1/3rd stop with just one plate.

[Brian C. Miller]

CJ, from a quick reading of Rockland's website tintype kit, they are using AG-Plus emulsion, and then using a reversal developer. Therefore, its either the emulsion or the developer which is messed up.

Make up a couple of plates.
Expose them normally.
Develop one plate in the Rockland reversal developer.
Develop one plate in a normal developer, like D-76.
Develop both a sheet of film and a sheet of paper in the Rockland reversal developer. (the liquid emulsions seem to be paper-type, but try it both.)

This will tell you if its the Rockland emulsion or the developer. If the problem is the developer, you could contact the people at Photographer's Formulary about reversal development, as they have a kit for Tmax film, and there might be something which could be used for liquid emulsions.

I have also noticed on Freestyle that there are also other liquid emulsions from Maco and Kentmere. Maco has a photographic gelatin for use as a primer on metal surfaces.

Another idea would be to expose a film sheet, and then contact print that to the emulsion on the metal sheet.

[Calamity Jane]

"Another idea would be to expose a film sheet, and then contact print that to the emulsion on the metal sheet."

That's a GREAT idea! Since I am 99.99% sure of getting a good B&W negative everytime, where a customer is involved, it means I wouldn't have to have the customer hang around while I fight with the tintype process.

I was thinking about trying to develop in Dektol (I just happen to have a package that isn't mixed yet) to see what happens.

Thanks for the tip about Photographer's Formulary - I'll see what they have.

[RichSBV]

A 'tintype' would not be a reversing developer. You'd wind up with black silver on top of black tin for a completely black photo. At best there would be a slight silver sheen to the dense areas.

For a true tintype, you'd have to bleach the silver completely so it's, well, silver on top of the black background.

The two alternatives I always wanted to try were:

Develop plate as 'normal' negative, then use a strong bleach.

Problem is, strong bleaches are very nasty...

Second: Develop as normal neg, then use a toner like Halo-Chrome that turns the silver, silver. Not as nasty as the bleaches and should produce the same result.

If Rockland is using a reversing devloper, then it must produce a very poor 'tintype' at best!

[Calamity Jane]

Rich: Over on my Tintype page ( http://www.geocities.com/winnonad/ ) , half way down, you can see a Rockland "tintype" (when the process is working well). The image develops, in the developer, as a positive - there is no reversal. I don't know what the chemistry is though.

[RichSBV]

I've been there and seen that ;-) Yes, it does look good. I've never really gotten into photo-chemistry enough to think of how Rockland does it? But if you think about a neg and reversing... A snowball would be a black spot on a neg so it can be white in print. If you do a standard reversal on the neg, the snowball would then be clear so it would be black in print. Transferred to tintype, you'd have a clear circle for the snowball on top of a black background. Wouldn't look right to me!

With the bleaching or toning, the snowball would still be solid silver crystals, but instead of being black, they'd be silver. On top of the tintype's black background, it would look right. The same for dark areas. They are clear on a neg, so nothing would happened once toned, and therefore still black on the tintype.

Either way, I hope you can get it all to work. And maybe someone can figure out what Rockland's developer is? I'd sure like to know ;-)

[Calamity Jane]

. . . me to . . .

[Harold_4074]

It was my understanding that tintypes were originally wet-collodion images on black "japanned" plates, which showed up as positives because of scattering by the silver grains in the developed (negative) image. The "reversal" of the image would be an optical effect of viewing like looking obliquely at a film negative against a dark background---the image appears positive by scattered light. An ambrotype works this way; the black background is painted onto the back of the glass, instead of the front of the tin in a tintype.

This is why I thought that a so-called physical developer might be appropriate; large, rough silver grains would probably scatter light better and thus give greater contrast and "density" in the image. I did a quick search with Google and did see a few references to physical developers used for wet collodion processes (like ambrotypes) but found nothing definitive.

A critical observation here is whether the image comes up negative by reflected light _before fixing_ or whether it appears as a positive from the beginning of development. If it is positive (against the light-colored unexposed background which clears in fixing) then there must be some really strange chemistry involved.

CJ: What would you expect if you coated a glass plate, and developed it in the tintype chemistry? My guess would be a negative, which would appear positive if viewed against a dark background. If, on the other hand, the image looks like a positive (shadows are black with the plate against a white background) then you have a true reversal process, and it is time to find somebody who really understands this stuff.

[Calamity Jane]

Harold: Nope, theRockland process it a true positive. The Ag Plus emulsion is a milky white in the unexposed state and, where exposed to light, it changes colour very little (it goes slightly tan). In the area of the picture that is dark, the developer seems to "eat away" the emulsion and let the black of the plate show thru. If under-exposed, the developer simply clears all the emulsion off the plate. There is no change in the image during fixing or rinsing.

If you were to coat a glass plate, the blacks would be transparent and the whites would be the colour of the original emulsion.

I am somewhat familiar with the wet plate processes (from reading) and this is TOTALLY different