View Full Version : Heresy and a resultant lab tip

Photo Engineer
01-05-2008, 07:12 PM
Here I am going to commit it!

When you work with silver gelatin, (at least at EK and in my own work) you will find that the melted gelatin with silver halide is viscous. I have made 6 batches of emulsion and found them to be identical and coated 120 sheets of paper to send out to testers and it must be identical as close as I can make it.

How do I do this with a viscous material such as melted gelatin?

I use weight/weight measurments to insure accuracy. So, in the dark, I weigh out the amount of solid unmelted emulsion and other ingredients to insure that I am getting what I want. After all, it is almost impossible to read a graduate cylinder in the dark! And, if I pour out melted emulsion, it is impossible to clear all of the emulsion out of the graduate. Adding water to rinse is a no-no. In fact, anything measured in the dark should be by weight.

Now, here is the real heresy to some readers.

Lets say I'm making up some HC110 from the syrup. I can always measure the syrup and then dilute it and rinse the graduate. Thats fine, but I find that if I make my own concentrates, the syrup cannot be rinsed at all and I lose some in the graduate, in fact sometimes quite a bit in proportion to what I'm making up. So, making syrups for storage can cause errors in the darkroom due to the fact that just like emulsions, the syrup or emulsion cannot be rinsed out of the volumetric measuring device.

I use weights to measure liquid ingredients for viscous concentrates that I store.

Just a lab tip for emulsion makers and those who make viscous concentrates learned by years of work in a really DARK room. And, it carries over, as you see, to the light darkroom.


01-14-2008, 02:58 PM
Perhaps is this idea a help. Beeing in the dark and to measure correctly low viscosity fluids for "production-process some hundred times" needs a specific tool.

Use a funnel with near the volume you need, on its undersite is a flap valve, upside the funnel on the edge is a long nose, necessary when you fill up with too much, this too much runs out (acoustic control in dark ? - now is full, when too much drops drop back into emulsion) and will not smear the outside of the funnel and drop too. If the funnel will have little too much volume, mount some little glas pearls or so.

Photo Engineer
01-14-2008, 03:01 PM
For this type of problem, I suggest syringes. I keep them handy and filled to the exact amount needed for an operation. Everything is filled beforehand. One photo from the DVD I'm preparing, shows the addition of Silver Nitrate solution using a syringe which was filled to the exact quantity in the light, then added in the dark.