First attempt with DCG

[jsfisher]

I finally took the plunge.

I was a little worried when I first sprinkled the gelatin onto the cold water. The whole thing turned to the consistency of gummy worms. I guess it is supposed to do that. Once the glop was up to a more appropriate temperature, things looked a lot better. After the recommended 45 minutes of stirring, the gelatin mixture was crystal clear, so I added the potassium dichromate. Oops, turn off the lights, dummy!

By the way, do you know how useless a red alcohol thermometer is under a red safelight?

And then there was the veil coating. It looks easier than it is, especially if you are using small plates. (I'm using large microscope slides, 2"x3".) Keeping all the gelatin on only one side is hard. Getting the gelatin to coat evenly on the side you really want is hard. Realizing you were having all these troubles under the dim glow of a safelight is hard, so I pressed on. I coated 14 plates, racked them up using one of those "comb binder splines" (I thought that was clever), then covered them to minimize dust contamination while the plates dried. Two hours later I re-racked them in a box and moved them to the refrigerator.

Next day, I remove the box from the frig to let the plates gradually return to room temperature. Meanwhile, I set up the laser to let it warm up, too.

Then, upon opening my box of plates, I find all the plates have shifted around and no longer neatly racked up. Many are lying on top of others; some are still sticky. I could say that most of the plates were ruined, but that would ignore that none of the plates were every right in the first place. Crestfallen, I sifted through the 14 plates one by one looking for the best of the bad. There was no point doing much with the junk I had created from the day before, but, by God, I was going to shine a green light on one of them before I recycled the lot.

I have only a feeble 10mW laser for this, so I'd set up for a 1.5" diameter beam illuminating a handful of socket-head screws. I'd planned to make a test strip of a sequence of exposures, but with only one plate worth trying, I said, "Screw it!", and went with 3 minutes flat. Three minutes later, the exposed plate is left to sit in the dark while I was getting the processing baths ready. Since my expectations were low, I decided to omit the rapid fixer step and the 50% IPA bath. That left just the water wash and the three -- 70%, 91%, and 99+% -- alcohol paths.

Half way through the water wash, I'm convinced there's no gelatin left on the plate. It looked like it must have all dissolved or lifted off. Heavy sigh. Well, the alcohol is already poured, so may as well continue. At IPA bath #3 (99+%), the lights come on, and I'm hoping to see any sort of hint of gelatin still on the plate let alone a flash of color to suggest something had been recorded.

Nothing.

I hit it with the heat gun anyway. The center of the plate started to darken. I thought I'd overheated whatever gelatin scum was still on the plate, and it was discoloring. But no! There in the middle of my plate was a 1.5" diameter area where, despite obvious problems with the coating, a handful of socket-head screws were clearly visible.

Despite so many problems, I made my very first DCG hologram! Who knew a sequence of frustration could be so enjoyable!

[Johnfp]

Congratulations!!!

Safe light? You really don't need much of a safelight for DCG. It acutally likes a little bit of light. For blue/green sensitive plates, use the 30 watt yellow bug lights. In fact I replaced all my lights down the basement with them (4) and never had a problem. DCG acutally likes a little light.

For the veil method, start to pour at the bottom of one corner. Come up the side as close to the side as you can, then go across the top and down the other side close to the edge. Then I put them on a record play at full speed (78) for a minute. This really helps even the stuff out. Then set them on a flat (level in both directions) surface. If you cover them, make sure the moisture can get out of the covering. You need them to dry and not be sealed in some environment that does not allow them to dry. I use a rack system that stores them horizontally one over the other with a separation. Then just put a piece of glass in the top rack and that keeps dust from falling on all of them.

I would not skip the fixing step, it is very important.

Good luck and keep up the good work.

John

[Jeffrey Weil]

Hello Jsfisher,

Excellent, on the first try too.

Don't be shy, we know its the first one, we know coating is hard.......we'll take that into account, promise......so, let's see a photo!

Jeff W

[holomaker]

In case you missed this , i made this one a while back. this is done under yellow "bug lights" as well, no need for darkness ......................

[jsfisher]

In case you missed this , i made this one a while back. this is done under yellow "bug lights" as well, no need for darkness ......................

What, are you kidding? It is a classic! I did you back and review it, though, and made a couple of very useful observations. Although coating a 2"x3" glass slide is a little different from coating a 4"x16" plate, I now see that it is mostly a matter of timing and flow up-across-down (mostly across) to get that curtain of gelatin flowing down at an angle and sweeping diagonally towards the bottom right corner.

With my second batch of plates, my technique was much improved. Of course, there was still room for other goof-ups. This time I dried the coated plates with my trusty heat gun. It's probably too hot; almost all the plates ended up cloudy. Still, there were a couple of good ones in the batch which I managed to shift towards indigo from over fixing.

It's all good, though, because (1) you can learn far more from you failures than your successes, (2) DCG is dirt cheap (compared to silver halide anyway), (3) I'm having fun. Number 3 is the most important. Hey, I also now have a bead on the conversion factor for my cheap-o lux meter to mW/cm^2 (for 532nm).

All in all, it has been an entertaining and educational week.

Oh, I have a question: Is this brain-dead or brilliant: Has anyone thought of / tried using a "mask" made from neutral density gel sheets (e.g. Roscoe #209) for making a sequence of test exposures all at once? A 4"x7.5" strip of ND.3 filter material, properly folded, would cover 75% of a 4"x5" with 1, 2, or 3 layers of ND.3 over each quarter. That would let you shoot 4 different exposures all at once each one F-stop apart. (Use ND.15 for 1/2 F-stop spacing.)

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[jsfisher]

Hello Jsfisher,

Excellent, on the first try too.

Don't be shy, we know its the first one, we know coating is hard.......we'll take that into account, promise......so, let's see a photo!

Jeff W

The actual looks far better, but you all know that already.

ScanImage02a.jpg (27.08 KiB) Viewed 4633 times

[Jeffrey Weil]

Hello Jsfisher,

Thanks for posting that. Looks like DCG to me!

Great start, keep it up and soon you'll be making super pro images.


Jeff W