Just very briefly. This is quite surprising and exciting.
That said, we should have known better: have a look at these patents by George Sawyer:
US 4178181
US 4835090
US 5449597
US 5494787
US 5605784
US 5629143
US 5658719
US 5849468
Quite a while ago I had listed several patents related to Lippmann photography (
https://holowiki.org/forum/viewtopic.php?t=5308). In the meantime, I had completely forgotten about Sawyer.
I should have known you had put that wiki page together! I've spent many hours going through those, especially at work when I'd rather be at home playing around with these things. Thankyou for doing that. Sawyer seems like he was an absolute monster, I wish I could have picked his brain a bit.
When it was suggested that I try out the mica, my mind actually went straight to this part of US 4178181:
"Reflecting materials suitable for application directly to the emulsion would be paint (metallic particles may be dispersed in rubber cement, as for example Venus 53" I was dangerously close to getting to the point of trying out the mercury-indium alloy that is also mentioned in the patent.
I struggled over the last couple of weeks and made countless batches of plates to replace the ones I was sharing earlier, but I kept falling short - I kept getting very yellow and unsaturated results, and I was struggling to figure out what I did wrong. I started working backwards, and ultimately determined that the hydroquinone I was adding to the emulsion to increase sensitivity seems to be to blame.
As far as I can tell, hq
does work, as the first half of the plates I was sharing a couple posts ago did not need any hypering baths, but for now I am omitting it, as it was causing more issues than it was solving. I think it's worth revisiting soon, however.
I haven't quite replicated the results I shared previously, but I'm getting pretty darn close. These are bright and colorful, but still fairly contrasty, so they have a lower dynamic range and a reduced ability to render more subtle mixed colors. But it's a lot better than whatever I was getting before!
"1.5x X into Ag, No Gelatin" seemed to have best tradeoff between producing small grains and a fairly clear emulsion, while still creating polydisperse grain sizes that cut down on the contrast a bit. 'No Gelatin' here refers to the addition solution ("B") during precipitation - the gelatin remains in solution A. Omitting the gelatin here seems to produce more pure blues over variants more in line with Darran Green's original recipe, which have gelatin present in both solutions. "1.5x Ag into X, No Gelatin" produced by far the best dynamic range, but the plates were very cloudy, with tons of halation, causing very dim colors overall.
Here are my notes for the "1.5x X into Ag, No Gelatin"
Precipitation
Solution A (250mL beaker):
- 4g gelatin
- 1.5g AgNO3
- 100mL water
Solution B (100mL beaker):
- 1020mg KBr
- 7.2mL 1% KI solution
- 80mL water
- Solution A was added to a room temp water bath with magnetic stirring to allow the gelatin to swell for a minute or two. Water bath was turned on to 40C until all the gelatin had melted
- Temperature probe added to Solution A
- Solution A was taken out of the heated water bath and placed in a cool water bath (cold tap water) to rapidly cool it back to room temp
- A syringe was loaded up with Solution B
- When the temp probe for Solution A hit 25C, it was removed from the cold water bath, and magnetic stirring set to 500RPM
- Going much lower than this risks the gelatin starting to set up during precipitation
- White lights off, red safelights on
- With the syringe tip under the surface of Solution A, slowly add in B over about 90 seconds
- Solution will cloud up, but should still be clear enough to see the magnetic stirbar spinning, and the temperature probe.
- Let it mix for another minute or two, and then pour the solution in a tray and set it in a refrigerator to gel up
Washing
I like to try and let it chill just long enough so that the gelatin has set up and not too much longer, to avoid Ostwald ripening that will start ocurring. For my little fridge this is about 90 minutes.
- Remove the tray from the fridge under red lighting
- Cut the gelatin into small cubes with a butterknife, about 1/4" or so
- Scoop the cubes into a 1L beaker
- Top it up with distilled water, mix it around, and let the cubes soak for 10 minutes
- Using a small spaghetti strainer, pour the contents of the beaker through it, allowing the cubes to collect and the excess water to drain off
- Repeat Steps 3-5 3 more times, for 4 total washes
- Add the cubes to a 250mL beaker
Note: I'm still seeing some crystallization on the edges of the plates, so maybe this style of washing isn't all that good, and a more traditional "noodling" would be better
Remelt & Finals
- Preheat water bath to 34C
- Add the beaker to the water bath with vigourous stirring (I'm trying to avoid the gelatin/AgX at the bottom and sides of the beaker from getting too hot
- Add temperature probe and watch it like a hawk
- The gelatin should melt between 28-31C
- When the solution looks like all the gelatin, add in the spectral sensitizers dropwise:
- 2mL erythrosine (1:1000 in water)
- 2mL 3,3'-Diethyloxacarbocyanine iodide (1:1000 in alcohol)
- 0.7mL 3,3'-Diethyl-9-methylthiacarbocyanine iodide (1:1000 in alcohol)
- 0.75mL pinacyanol chloride (1:1000 in alcohol)
- Note: Darran green has suggested I add these in reverse order to potentially cut down on my contrast issues (I haven't tried this yet)
- Add in 20mL 1% solution of chrome alum
- Let it mix for a minute or two, and the pull it off heat. Pull from heat if it hits 34C - this time I was quick enough to keep it around 32C the whole time.
Coat the solution on glass plates. I use about 25mL per 8"x10" piece of glass, and scale down proportionally for smaller pieces. Try your best to tip the plates around and avoid using your finger to spread the emulsion, as that can cause bright spots on the plate - I still do this along the edges that the emulsion refuses to spread out on. I do this under red safelights that are as dim as possible, while still being bright enough to comfortably see what I'm doing.
Give it a while to gel up, then put them in a drying box with some airflow and let them dry for several hours (usually overnight for me).
Mica & Processing
After the plates are dry, I cut them down to size with a "Beetle Bits" glass cutter, emulsion side up.
The plates I intend to shoot over the next day or two are hypered in a 0.05% solution of ascorbic acid (100mg in 200mL water) - 2 minutes with agitation.
The plates are left in the bath while the mica is applied 1 by 1. Pull a plate from the bath and blot it between some paper towels to remove most of the extra drops. Tip a small amount of mica powder (I'm using Mehron metallic mica powder) onto the plate and massage it around with a gloved finger for 30 seconds or so. Set vertical and repeat for the rest of the plates.
Once the plates have all the mica applied, use a very soft brush and gently remove all the excess mica. Set in a drying box for 1 hour with airflow.
Expose. This batch seems to take about 12 minutes @ f/2.8 in EV12 lighting.
Development
Before development, remove the excess mica from the plate. I use a cottonball soaked in 99% isopropyl alcohol to wipe the majority of it off, and then a second dry cotton ball to dry the plate off.
I use GP-2 as a developer, but I keep the ammonium thiocyanate as a separate 3% solution so I can tweak the solvent level.
GP-2 working solution:
- 10mL GP-2 Stock
- 5mL ammonium thiocycante 3% solution
- 50mL water
Develop with agitation. It's about 2 minutes for me right now, but also my basement is pretty hot right now with the heat wave. 2-3 minutes is a good starting point.
Wash
Fix for about 1 minute with a 5% solution of hypo
Wash
With a wet cotton ball and a couple of drops of dish soap, gently rub it all over the plate and remove the remaining traces of mica powder
Wash
Fan dry.
The previous plates needed to be swelled, but they were older and I think the gelatin had hardened quite a bit, so I think there was a lot more interstitial area in between the mica particles for air-gelatin fringes to occur. All these followup plates seem to take on a lot more mica, so this hasn't been necessary.
That's all I've got at the moment, I'll update and add in some more images from this batch as I make them. I'm curious about varying the KBr:KI ratio to see if I can increase dynamic range a bit without nuking grain size. I'm also interested how much AgX I can push into this recipe before it starts having issues.