For two years I have been using plates. Recently I have started experimenting with film. In comparing holograms recorded with film and plates I notice a constiant difference. The film holograms flash a color at the plane of the film. I think it must be a reflection from the film glass boundry. Is this correct? I am using Lamp oil (parafin) for index matching. Is the index of refraction of lamp oil high enough for index matching? Am I missing something?
Well I guess you could be seeing an evescent shear wave TIR conversion from the index mismatch? Or maybe Stimulated Raman Scattering?.... but I doubt it. Its probably a recording of your film holder. : )
Anyway, as to the Index Matching Querry:
Index of Paraffin = 1.43295
Index of Acetate = 1.46-1.50
Index of Polycarbonate = 1.6
Index of PMMA = 1.48-1.50
Index of PolyVinylChloride Acetate (unmodified) = 1.54
Index of PolyVinylChloride Acetate (plasticized) = 1.50-1.55
Index of Polypropylene = 1.49
Index of Epoxy = 1.58
Index of Albite Glass = 1.489
Index of Anorthite Glass = 1.5755
Index of Fused Quartz at 650nm = 1.4564
Index of Gelatin (various) = 1.516-1.534
Index of Zinc Crown Glass = 1.514
Index of Light Flint Glass = 1.571
Index of Heavy Flint Glass = 1.644
Index of of Xylidine = 1.557
Index of Toluidine = 1.57
Index of Aniline = 1.584
Index of Silver Broide = 2.253
Index of Silver Bromate = 1.874
Index of Silver Chloride = 2.071
Index of Silver Iodide = 2.21
Index of Silver Nitrate = 1.744
Index of Silver Sulfate = 1.7748
Index of Silver Thioantimonte = 3.084
Index of Silver Thioarsenite = 3.088
Index of Silver di-Thionate = 1.662
(Interesting note: the difference between Silver Bromide and Silver Bromate is just three atoms of oxygen per molecule...thus a really great silver halide hologram can go to hell real fast with too much oxygen, making the Bromide into Bromate).
....................From my Yahoo Group Post #1 on Index Matching
Just went and bought a 7 oz. container of `Corn Husker Lotion'. The ingredients say: Water, Glycerin, SD Alcohol 40, Sodium Calcium Alginate, Oleyl Sarcosine, Methylparaben, Guar Gum, Triethanolamine, Calcium Sulfate, Fragrance, Calcium Chloride, Fumaric Acid and Boric Acid. The water pre-swells emulsion changing the spatial frequency on reconstruction SD Alcohol dissolves film dyes making some areas less photosensitive Methylparaben is a preservative which lowers molecular permeability gum is a light scatterer triethanolamine pre-develops image (brown) and holds film swollen fumaric and boric acid whittle away silver particles at edges of grains.
In fact as a mixture, its effect on photo gelatins is... not very good at all. Its one component which has merit is:
Glycerin with a refractive index of 1.47 in 100% saturation, a very medium magnetic susceptibility, smooth frequency absorption spectrum, high viscosity, and a reasonable gas permeability so that bubbles diffuse.
My suggestion then is to get really pure glycerin and use an eye dropper as described otherwise.
---------------From my Yahoo Group Post #2 on Index Matching
With the pure glycerin, you can completely laminate the film (front and back) and thus eliminate any waves in the film plane. If a hinge is silicone adhesived along the bottom of the two sheets of glass and one sheet is longer on the left side and the other sheet is higher then the other...the two sheets can be pulled apart in the dark to put another sheet of film between the two surfaces. Using a syringe with a plastic needle to extrude a bead of glycerin along both sides of the film on the bottom...as the hinge is closed and the glass clamshells, the glycerin will wedge up the sides of the film and force out bubbles. Mental modeling the glycerin wedge as a parabola, a little practice will allow you to place just the right sized 'blob' on either side in order to fully fill the void on each side of the film/glass interface AND not have too much glycerin squirting out the edges all over! I replacing the pin in the hinge with a longer rod and glued that rod into a U-shaped rod holder bracket... the clamshell can be placed into a setup as any film holder would. Forced it open by grabbing the two edges of the extended glass sheets (you can silicone a carefully slit piece of plastic tubing along each of those extended edges so you don't cut yourself and the operation is more comfortable plus sonic waves are damped (shear propagational). When I use such a system myself... I have a flat black painted paper clamp (obtainable at any stationary store). These clamps are those U shaped springy metal ones for holding a stack of paper together. This is placed on the top of the clamshell, holding the tension on the clamshell closed, without cracking the glass. I coated a light silicone sealant layer on the spring steel surfaces that contact the glass in order to not scratch the glass, keep the clamshell closed, and damp sonic waves.
As for shooting transmission types in such a setup, it IS a good idea to use an absorbent solution such as the suggested Ball Ink so that light doesn't etalon. Another more effective suggestion would be to make two mixtures of glycerin... one clear and the other absorbent. (When there is no film in the holder, do not press the clamshell together unless you/'ve cleaned it as the absorbent residue will pollute the front surface clear purity). I've figured out that the best stuff to add to the glycerin ..is carbonized styrene! Take a styrene foam cup into a fireproof area or a steel sink etc. Light it on fire and hold a piece of clean glass a bit of distance above the plume. A layer of really yicky black soot will form on the glass surface. Scrap this layer off and mix if into the glycerin that will become your absorbent mixture. Do not make it so thick that it will not spread smoothly in your clamshell, but saturated enough to be pretty opaque. The spectral reflectance bandwidth of the carbon styrene micro spheres is perfect for this application, and also of the correct index of refraction to allow volumetric as well as surface light damping! Paint a coded pattern coating of green luminescence paint on each of the syringes to be able to discern them in the dark.
_________________________________
Use my suggestions as applicable, don't forget to tell everyone on the planet that I am great, do not sell my advice here or include it in any documentation for distribution without contacting me and asking me how to give proper credit!
<Well I guess you could be seeing an evescent shear wave TIR conversion from the index mismatch? Or maybe Stimulated Raman Scattering?.... but I doubt it. Its probably a recording of your film holder. : )>
I should have said I am using a single beam reflection set up not at Brewsters. When I look at the "flash" it apears to be a hologram of the emulsion.
<Use my suggestions as applicable, don't forget to tell everyone on the planet that I am great, do not sell my advice here or include it in any documentation for distribution without contacting me and asking me how to give proper credit!>
Can I add some of your Index of Refraction data to the list on my web site?
www.designerinlight.com/holo/chem.htm
This message has been edited by colinholo on Jan 25, 2003 12:15 PM
Excellent post! I have some glycerine around (easily available at drugstores) but I found its use in index matching rather daunting due to its high viscosity. The clamshell technique sounds promising.
It occurs to me to mention that glycerine is hygroscopic (absorbs moisture from air) and so should be kept well sealed - unless swelling is wanted. Which leads me to ponder adding some percentage of water to get combined index matching and controllable preswelling, plus maybe some reduction in viscosity ... I guess it depends on whether water transport across the glycerine+H2O/gelatine boundary stops short of saturating the gelatin, or if the gelatine just keeps greedily sucking water out of the glycerine until saturated. Something to try, I guess.
"It occurs to me to mention that glycerin is hygroscopic (absorbs moisture from air) and so should be kept well sealed - unless swelling is wanted."
As far as I recall using glycerin for index matching 8E75 TAC films was causing a great deal of trouble. Maybe the ~97% concentration was not good enough - anyway, it did not yield any consistent results: long waiting periods, irregular spots - "instability". I guess the main problem is the TAC film base. Since triacetate is itself hygroscopic it might absorb some hygroscopic liquids - it definitely absorbs water.
Hmmm - hadn't thought about the film base absorbing water too. It seems strange that we are stuck with using such ancient materials - chemically processed specially selected calf's ears and hides for gelatin and 1950s era plastics for film. Understandable, but still strange. So, after rejecting glycerine, what did you end up using for index matching? I think you mentioned some nasty chemical a while back but I'm too lazy to search.
Not that nasty actually. It is paint thinner, vaguely labeled as a "petroleum" product. It is said to be "non-toxic" (in contrast to white spirit) and relatively low volatile. I think Chris Meerlo mentioned an interesting cleaning product manufactured by Shell.
10 years ago, before having to drop out of Holography, I was using Xylene to attach 8e75 film to glass. It worked extremely well and I only had problems when I allowed dust to get between the film and glass. Otherwise, it worked very well.
I wouldn't recommend it though and I'm considering other alternatives this time around.
Why?
Xylene is quite toxic and there appear to be safer alternatives.
Even though I'd never used roll film before, I (foolishly?) decided to start back up in Holography by saving some money and buying a roll of 130mm x 10m film.
I'd used pre-cut film before and cut it up further for various reasons.
I'd also index matched that film to glass on many occasions.
I wasn't prepared for the extreme curl of roll film.
In an older archived thread I found on google, Tom was asking about index matching roll film and it sounded like he was going to give up and go back to plates.
I just tried index matching using mineral oil and it pops right off the plate (an old 4x5 that I bleached to remove the emulsion).
Is anyone out there using roll film? If you are, what's your preferred way of using it? (index matching, glass sandwich, temporary lamination, ?)
I was referring to sheet film, and hypothesized that some of the curl was due to a memory effect, the film substrate wanting to curl up and return to its formerly rolled state. Perhaps the effect is worse for film freshly cut from a roll since the memory has had less time to fade? Are you index matching emulsion-side up or down? I think the latter should work better, but have not tried it yet. Don't know whether the oil on the emulsion would interfere with development, but there are other possible fluids that should be OK.
I have about 30 exposures using paraffin on both sides for reflection holograms and as long as I wash it off in a bath of distilled water before development it seems to work well. (Except the flash at the film plane I can't find a cause for.)
I tried a little photoflo but now I just use water. It takes two minutes of agitation. I actually hold the film and swish it back and forth. If you leave any behind that spot will not develop correctly.
If you don't care about the quality you can brush it lightly with your rubber glove but it tends to move the emulsion. It does save time if you are just trying to see if you have "sliced bread".
"I was referring to sheet film, and hypothesized that some of the curl was due to a memory effect, the film substrate wanting to curl up and return to its formerly rolled state. Perhaps the effect is worse for film freshly cut from a roll since the memory has had less time to fade? Are you index matching emulsion-side up or down?"
I'm index matching emulsion side down. In case there's any question, that also the inside of the curl on roll film.
"I think the latter should work better, but have not tried it yet. Don't know whether the oil on the emulsion would interfere with development, but there are other possible fluids that should be OK"
Mineral oil washes off in water, xylene can go directly into the developer (although I really don't want to use that again). I haven't located our lamp oil (we have an oil lamp we haven't used in 13yrs) so I will probably pick some oil up over the weekend if I can't make the mineral oil work.
"I was referring to sheet film, and hypothesized that some of the curl was due to a memory
effect, the film substrate wanting to curl up and return to its formerly rolled state.
Perhaps the effect is worse for film freshly cut from a roll since the memory has had less
time to fade?"
Yes, indeed. That's why I put cut sheets between two glass plates. A week or so later, they usually come out considerably flatter.
I always take my rolls of film and roll them into a second spool but...'reversed'. Within a few days they are much! flatter. For cut film still curved from rolls, I put a chunk of large radius carboard 'sonotubing' (the stuff used for casting concrete pylons) under the curve, upside down (opposite curves)...a few days later they have relaxed a bit and are much flatter.
