View Full Version : DVD of making and coating

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Photo Engineer
12-27-2007, 08:59 AM
Thanks Ben. I'll give it a try.


Photo Engineer
12-27-2007, 09:50 AM
With my thanks to Ben, here are two stills from the DVD in progress.

These pictures were taken with a red flashlight safelight and my normal yellow safelights. The camera was in IR mode, so the emulsion is hopefully not fogged.

The first picture shows the syringe posed over the beaker before precipitation starts and the second shows the precipitation in progress. Hopefully you will see the white cloud of emulsion being formed in the beaker.

This was a 600 gram make of the emulsion which should make about 100 8x10 prints and should keep for 6 months. I made 2 coatings which are waiting to be tested.


12-27-2007, 09:55 AM

Kirk Keyes
12-27-2007, 11:38 AM
That's great! I love the mad scientist side lighting!

Photo Engineer
12-27-2007, 02:25 PM


That is the same red filtered flashlight you held for me during the workshop and I'm making the same formula as I did then. Only here, I have it balanced on another object. You were not around to help me. :(


Photo Engineer
12-27-2007, 02:44 PM
I've been asked by so many, how the blades work in detail.

Here are two still frames taken during a practice session for the DVD. I am using 10% gelatin, tinted with food dyes for visibility.

The first picture shows the blade being charged with 12 ml of "emulsion", and the second one shows the action of drawing the blade across the paper to create a finished 8x10 coating. Defects are to be expected at the top and bottom of the 'run'. In fact, coating defects of this nature occur even with a full production coating machine due to starup and shutdown.

The black marker lines on the coating indicate to me, in the dark, where the good and bad coating can be found. I always coat wider and longer than the desired coating size.


12-27-2007, 04:24 PM

This just rocks! I'm so glad you are making this video!

Removed Account
12-27-2007, 07:30 PM
Good gosh, Ron! This looks amazing, like something I would watch even if I didn't have an interest in emulsion making (which I do). Are you taking deposits? :D

- Justin

Photo Engineer
12-27-2007, 08:34 PM

Thanks for all the nice comments.

I want you to know that I know how to make and coat more elegantly than what you see above, but what I'm trying to do is make it nearly foolproof and doable in a small home darkroom.

Therefore, it will al be done with a minimum of chemicals and equipment. In fact, the most expensive item is the hotplate/stirrer you see in my post 22 above. And, of course the silver nitrate! That is also expensive.

Well, just to let you know that to satisfy myself that the IR and heavy red safelights were 'safe' I just finished processing two prints and a wedge spectrogram of the emulsion made during the shooting session and it is absolutely normal.


12-27-2007, 11:03 PM
This is really cool mad scientist stuff.
Just can't wait to see the finished video.


12-28-2007, 08:56 AM
I'm glad VLC worked. The image quality looks pretty good on these.
I can't wait for the DVD to come out :) I think the term "Captive Audience" doesn't even come close...

Photo Engineer
01-03-2008, 09:02 PM
In post #26, I show the coating blade in actual use, but I'm still getting off-line comments and questions about this re: how does it really work and why is it better, or something to that effect.

Well, first, the blade has a well that is 1/2" deep by the width of coating desired + a fudge factor for selvedge. So, an 8" blade is actual 8.25" wide and the well is therefore 1/2" x 1/2" x 8.25". The well will hold about 40 ml allowing gaps of the endcap up to 20 or 40 mil. This is to allow coatings of carbon which requires more fluid.

The edge towards the operator is heavy. For an 8" blade it weighs about 2 pounds (1 kg). That serves two purposes. One is to keep the motion smooth from inertia and another is to keep the paper spread out and level as the blade advances. The end cap is adjusted to have gaps from usually 5 mil to 20 mil or even higher, but above about 20 mil, the surface tension is not enough to hold the emulsion in the well and it will leak.

It is designed to work with between 5% and 12% gelatin for optimum coating and is designed to work at about 65 - 75 deg F. If you overheat, the paper will wrinkle and the emulsion will run especially on film support. The blade should be at about 105F when you pour in the emulsion. A cold blade will set up the emulsion and cause streaks and defects.

The tolerance of the blade is 0.001" and any blade out of tolearance is a reject.

Now, if the leading edge towards the operator were to be missing, that is if it was just an undercut blade and not a contaniner, then the puddle of emulsion poured on paper will spread and will cause swell and create a huge defect at the start of the 'run'. As the paper swells, the paper moves closer to the blade and the blade scrapes off emulsion leaving too little causing streaks in the middle. If the blade is adjusted unevenly, you will see more or less emulsion at the edges. But, basically the blade is designed to allow surface tension of gelatin with the right viscosity to 'pull' the emulsion into evenness. Doing this takes practice. So this is why I suggest and demonstrate on the DVD, the use of the blade in the light with dyed gelatin to learn before you commit with emulsion.

These blades were used at Kodak in the 20s to coat up to 42" wide film and paper with trough coaters. I am currently coating up to 16"x20" sheets and I admit that beyond 8x10 the difficulty goes up. Typically, with an 8x10, I use an 11x14 sheet to allow for edges and over and under run.

The bottom line is that this is an art and takes practice, and the larger the blade the more practice.


richard ide
01-03-2008, 10:18 PM
Absolutely fantastic that you are making this technology available to us. Can you hear my audible drooling for the DVD? I think I have all the chemistry on hand including about 100 gms of cadmium chloride inherited from my grandfather. Now to just move this farther up the todo list. Many thanks.


Photo Engineer
01-07-2008, 03:57 PM
Well, 3 more hours today, and another 2 or so tomorrow should pretty much wrap things up.

Today, we finished the taping of the ISO 40 ortho film and iso washing. I will have stills of that tomorrow or the day after to post. We also have a lot more to show.


Photo Engineer
01-07-2008, 07:57 PM
Here are some pictures for you.

The first is of the reactor ready for addition of silver nitrate and ammonia. The reactor contains KBr, KI, and PA Gelatin. This is a special gelatin that allows washes to be done more easily.

The second is a picture of the emulsion being washed. The coagulum (emulsion + gelatin) is hanging as a mass from the stirring rod while the salts remain behind in the water. This wash is repeated several times with cold distilled water, and then the emulsion is reconstituted and diluted to the proper concentration and then sulfur sensitized and coated.


01-07-2008, 08:29 PM

This stuff is Fascinating!!! Can't wait for the DVD. Thanks!

01-07-2008, 10:04 PM
I am ordering two! One to store, and one to wear out from watching it.

Bob M.

Photo Engineer
01-08-2008, 03:01 PM
Two hours of tape finished today at 12:30 PM. We will have to reshoot some scenes and edit, so a finish date of mid February is in sight. I'll post some interesting pics here as I go through the footage (meterage?).


01-08-2008, 04:42 PM

I have to ask....is a book of some sort going to accompany the release of the DVD?

Bob M.

Photo Engineer
01-08-2008, 05:32 PM
Oh, I thought I said this before. The DVD and book will be sold together.