If I said that it relied on swelling agents, Isoelectric point and the relative solubilities of the ingredients related to cations what would be your response?
PE
If that was all you said, I probably wouldn't respond at all.
But I would be happy that we were at least facing the same direction.
Why is "no" such a hard concept? Is it the "n"? Is it the "o"? Is it the two letters together? Perhaps it is the order of the letters.
A reason is given. It is ignored or not enough. Accept the reason whether or not you like it. For reasons that can't be stated or that you cannot understand you cannot let it go. How is this working for you?
PE freely shares a lot of information with us. If he can't or won't share some of it => get over it. Are you just trying to drive him away from APUG??? Would that make you feel better?
Steve
Warning!! Handling a Hasselblad can be harmful to your financial well being!
Nothing beats a great piece of glass!
I leave the digital work for the urologists and proctologists.
Last edited by PhotoJim; 07-01-2009 at 11:28 PM.
Reason: Withdrawn.
Jim MacKenzie - Regina, Saskatchewan, Canada
A bunch of Nikons; Feds, Zorkis and a Kiev; Pentax 67-II (inherited from my deceased father-in-law); Bronica SQ-A; and two crappy 4x5 cameras with very good lenses (a better camera is on the list).
Frankly, I have been up all night working on a new emulsion formula series.
Ray - Let's take that thought over to the Emulsion Making forum and talk about that. I've been working on one emulsion formula for the last year and a half, so I'm interesting in hearing about your series of formulae. WHat are your goals, and what have you done to try and achieve them?
I've made 3 iterations in my emulsion goal (to make a t-grain emulsion is my goal), and mostly at this point, all 3 iterations made major improvements in the actual physical techniques/equipment used, and probably much less improvement in the actual emulsion. Still not a lot of t-grains in the emulsion, but I have great hopes for the next iteration!
Anyway, let's talk about this for a bit!
Kirk
Kirk
For up from the ashes, up from the ashes, grow the roses of success!
I have posted this graph before on APUG and Photo Net illustrating the effects of pH on the fix rate, wash rate and swell of bone gelatin in photomaterials.
This comes from a site in Australia and was passed on to me several years ago by someone. The site is concerned with archival properties of primarily motion picture film and has studied fixers wash rates as a function of pH.
Thus, this is a graph that encompasses all 3 characteristics of any photo product using bone gelatin, on a relative scale based on thickness and hardening. Rate/swell goes up reading left to right.
If you wish to use Porcine gelatin, then flip the chart on the X axis and it will roughly reflect the differences in the two gelatins. In the case of the pig gelatin, the minimum, instead of being at about 4 pH units would be at about 9 pH units.
I have posted this graph before on APUG and Photo Net
illustrating the effects of pH on the fix rate, wash rate and
swell of bone gelatin in photo materials. PE
The graph only deals with the swell of the gelatin and that with
regard to it's gain in weight. The graph deviates considerably
from one included by Dr. Robert Chapman in an article for
Photo Techniques. Both do agree though on the ph of the
isoelectric point, give or take some little.
His article dealt with older emulsions and today's hardened
emulsions. Dr. Chapman holds a doctors degree in chemistry
and has worked for DuPont's and Unicolor's product research
departments.
I've the article to locate. Will make an effort to post. Dan
The graph is good enough considering the huge variation in Bovine gelatin around the world, the huge variation in the type and quantity of hardener used and gelatin coated and etc. This figure represents a good enough approximation for our purposes.
I have run tests regarding weight and swell both, and have done them with and without hardeners at EK and I could draw a generic family of graphs that fit the one posted above. I have run hardness tests vs pH as well, and wash vs pH etc. etc.
The bottom line is that one can track wash rate, fix rate and swell by means of the above graph and it fits well with experimental results.
Looking up something else I spotted that Kodak Research showed that increasing the level of other salts, and the buffering can also reduce the swell of the gelatin during fixing. The Research was done by A.Green & G.I.P.Levenson & published in 1968, I've not seen the research paper.
This could indicate that TF-3 might actually be better than TF-4 with it's higher level of buffering.
Specific salts cause swelling and others decrease it. For example, Sodium Sulfate decreases swell, but Sodium Sulfite has little effect. Potassium Sulfate decreases swell but also can virtually stop fixing. Potassium ion in fixers can poison them. This is found in several texts on the subject.
Mees and James show that fixation is a function of a "U" shaped curve with rate the Y axis and concentration the X axis. There is an optimum point for fix rate and at either end, you can slow it down.
So, saying TF4 or TF3 (or TF5? ) differ or one is better than the other would have to be shown experimentally. The borax buffer in TF4 adds stability. That I have proven to myself, but I never compared them for activity.
Originally Posted by Photo Engineer
Adv Reply
) differ or one is better than the other would have to be shown experimentally. The borax buffer in TF4 adds stability. That I have proven to myself, but I never compared them for activity.
