If a SH film hologram continues to shift color... ? August 5 2003 at 5:07 PM
Michael Harrison (no login)
I've got a few holograms I've made recently that go though the following development regime:
1) 3% TEA soak
2) Dry
3) Expose
4) Pre-dev rinse (to remove the TEA)
5) Develop D-19
6) Stop bath, 10% acetic acid
7) Rinse
8) Bleach (JD2 see http://www.designerinlight.com/holo/chem.htm#jd2 )
9) Rinse until clear
10) Alcohol baths (50%, then 100%)
11) Squeegee & air dry
Something I've noticed of late is that the holograms continue to "age" in that one that starts out a golden color will continue to shift to green (in at least one case a bright emerald green) over a period of 24 hours.
I've tried rapid drying with a hair dryer thinking that I'm somehow seeing gradual moisture loss but was never able to get the hologram to shift farther than a red-yellow color under the dryer. As the day has worn on though, the hologram has continued to shift and now a red-yellow hologram is more yellow than red.
Re: Re: If a SH film hologram continues to shift color... ?
August 5 2003, 10:11 PM
Could the outgassing be caused by the use of a stop bath in the process? I remember hearing that acid stop bath used with sodium carbonate based developers like D-19 liberate carbon dioxide micro-bubbles, which increase scatter. Maybe the little bubbles are bursting over those few days, collapsing the fringes and wafting their contents out into the air! 8^)
Re: Re: Re: If a SH film hologram continues to shift color... ?
August 6 2003, 2:19 AM
That's easy enough to test for and I'll do that this morning.
I also wonder if it's a case of using old developer. The D-19 I'm using is at least six months old, although it has been stored in a refrigerator for most of that time and I've only removed a weeks worth at a time (I transfer about 500ml to an "active" bottle and leave the rest in the fridge).
Re: Re: Re: If a SH film hologram continues to shift color... ?
August 6 2003, 4:45 AM
The 'wonkey' thing about film, is that moisture is always moving in and out of it. When the 'environmental humidity' is high or low, moisture moves in and out of the film at different rates. All I was doing with my suggestion, was coming up with a quick fix assessment for your perceived, 'slow shifting of interfringe spacing' mystery. Corrosion of your chemical purity so that moisture takes longer to cross its boundary, will also cause slow shifting even in the face of supposed elevated drying temperatures. Slime, algae, fungus, soap scum, poor rinsing, oily residue, unfiltered water! .... will also retard the osmosis of moisture out of your emulsions.
I think it's the relative humidity, too. Has the humidity in your part of the world gone down, ie are you having warm, dry weather? Or are you storing the holograms in a warmer and/or dryer place than usual. I'm curious, though about the hair dryer approach. Do you mean it starts as a kind of orange and shifts toward yellow - about a 10 or 20nm blue-shift? The fact that it continues to blue-shift seems to indicate slow moisture loss. The hair dryer may simply have shifted the dynamic, ie the rate of natural osmosis. Natural osmosis is exponential so that the greater amount of gas comes out quickly then the process slows down. You've probably seen this in helium balloons where the initial deflation is pretty rapid, then it just sits on the floor and doesn't deflate all the way for ages. By hitting it with a hair dryer, you may have removed moisture at or near the surface, causing a slight blue shift and then the moisture buried more deeply has to come to the surface and then osmose (or whatever the verb is!).
Bagging it with a dessicant seems a good idea. If we're correct, then the moisture exuded by the hologram will go into the dessicant. There should be a relationship between the blue shifting of the hologram and the color shift of the dessicant, until, of course, the dessicant can absorb no more moisture.
"I think it's the relative humidity, too. Has the humidity in your part of the world gone down, ie are you having warm, dry weather?"
We are experiencing warm dry weather (it's supposed get to a high of 108 today). I'll have to bring my hygrometer into the office tomorrow to see how the humidity differs from my lab.
"Or are you storing the holograms in a warmer and/or dryer place than usual."
Nope, same as I have been for several months. Once the film is dry and the image clearly visible I wait another 30 minutes and back it with Oracal 651. After that I usually stick it between two pieces of glass for ease of viewing during the day (otherwise the film curls and makes viewing the image a pain).
"I'm curious, though about the hair dryer approach. Do you mean it starts as a kind of orange and shifts toward yellow - about a 10 or 20nm blue-shift?"
Yes although they usually end up as green where they started as either red or reddish-yellow depending on the particular exposure and processing times.
"The fact that it continues to blue-shift seems to indicate slow moisture loss. The hair dryer may simply have shifted the dynamic, ie the rate of natural osmosis."
I haven't used the dryer with all the holograms I've done recently although all seem to exhibit this behavior to a greater or lesser degree (I've only recently started using the dryer and haven't noted it on all the data sheets I've used it. I am now.)
"Natural osmosis is exponential so that the greater amount of gas comes out quickly then the process slows down. ... By hitting it with a hair dryer, you may have removed moisture at or near the surface, causing a slight blue shift and then the moisture buried more deeply has to come to the surface and then osmose (or whatever the verb is!)."
I try to minimize that effect by aiming the dryer at the back of the film. I haven't done any tests to see if drying one side or the other gets me different results though.
"Bagging it with a dessicant seems a good idea. If we're correct, then the moisture exuded by the hologram will go into the dessicant. There should be a relationship between the blue shifting of the hologram and the color shift of the dessicant, until, of course, the dessicant can absorb no more moisture."
I noticed something interesting this morning that may be related to the moisture issue. After I had processed and rinsed my last hologram of the morning, I put it through two alcohol baths. One 50% alcohol/distilled water and the second 100% alcohol (with a few drops of photo-flo). Each one lasted several minutes. I was hoping that this would help to reduce the shrinking effect I was seeing.
What I found though was that the alcohol had apparently hardened the emulsion such that after drying I had a deep red image no matter how much time the film spent under the dryer and I let it sit for many minutes. This was with a regime that should have given me a light green image.
Thinking to myself "odd" and deciding that wasn't what I wanted, I gave the hologram a spritz from my distilled water/photo-flo bottle, let it sit for a moment and squeegeed it off. After drying I ended up with a nice green image staring at me. I don't really understand why though. I had expected that the alcohol baths would have sucked the water out of the emulsion and resulted in the same green image I finally got.
Unfortunately I had to dash off to work and I have had a chance to peruse the literature to see if theres a clue to why there wasn't any color shifting when I used the alcohol baths.
The alcohol thing is odd. The first hologram I made were on Agfa 8E75 developed with D19 and bleached with Pot Dichromate/sulphuric acid (just like yours). I washed with water and photoflo. These turned out deep red. Never tried the "spritz" test. Later I used Agfa with pyrogallol and the same bleach. I washed these with 100% IPA but with no photoflo. these turned out from red to deep yellow-orange, depending on the amount of Sodium Sulphite I used. However, I never dried with two alcohol washes with photoflo.
One idea that occurs to me is that the alcohol drove the water out from the surface of the emulsion thus creating a "crust" that trapped the water underneath. When you spritzed it, the "crusty" top layer re-humidified, softened and alloweed the trapped water to be released. I'm also wondering whether the long time you zapped it with the hair dryer made the "crusty" layer harder and maintained the trapped water underneath, like leaving a pie too long in the oven.
Photoflo has propylene glycol in it which is like a slight oil slick that prevents water from easily passing through it, especially when baked. But its not a huge effect. To see life without the Photoflo.... get some Baby Shampoo and mix a few drops with a litre of water. Remember also that Photoflo is really quite yummy! for fungus and such as I first stated, and once populated with them, the love continues!... as they also think emulsion is just wonderful!! a real desert taste treat! Which of course brings us to.... more cool HoloTricks!..... This Week, we investigate...> Alternative Holographic Processing, via Critters! (such as E coli!) : )
Shoot a Hologram, develop it, stop it, fix it, rinse it, but don't bleach it. Prepare a solution of watery E coli (be careful, but resourceful... you will find most people do not like to contribute such 'resources' even in the name of science or art, unless its verbal/written, which will not help with this great work), and dip the Hologram in it... let it sit over night (or so). Now, take it out and dip it in a mild solution of Formaldehyde.... then rinse the heck out of it. The bacteria should have munched on the emulsion but left alone the areas with silver in them. When you rinse and then dry the film, the areas that were munched! should collapse, while the areas with silver should remain supported! The difference in shrinkability, leads to the surface of the emulsion mirroring the volume of the support under it and so ...an analog matrix transformation is formed...
>>>>>>>>>>>>>Insto-Surface Relief Holograms!
...... ready to metal plate and Emboss with!
And what I find especially cool .... is that IF this idea is full of ****!, ....no one can say so by posting that 'four letter word', as the site will disinfect it! and thus deny them the satisfaction thereof! lol
The efficasy of Ecoli to do the job of providing a ultra natural, and ecologically wonderful! 'Surface Relief Hologram', can be augmented through the use of 'Pseudomonas' (another form of bacteria that consumes hydrocarbons)....especially if the Ecoli bath contains some raw oil slick and nasty sewage! Here is a seperate application of 'Pseudomonas' .... little do they know they are evolving the Ultimate Holographic Processing Solution for the 21st Century!
"Tumeo found oil-eating Pseudomonas on a diesel spill between two storage tanks at McMurdo Station. Since no
natural sources of oil have been found on Antarctica, Tumeo thinks the bacteria he found may have hitched a ride to
the continent on an oil tanker. The multinational Antarctic Treaty prohibits exotic species from being introduced to the
continent, but since Pseudomonas are already there, Tumeo is hoping to use them to clean up some of the fuel spills
that have occurred since McMurdo Station opened in the 1950's.
His work, which is featured in a recent issue of the British journal New Scientist, involves 12 wooden boxes. Into
some, he's added the following unsavory ingredients: a cubic foot of diesel-soaked soil, sewage, and surfactants,
which are chemicals that break the surface tension of the soil to allow bacteria easier access to the diesel fuel.
Tumeo's goal is to create an environment in which the bacteria thrive. At the South Pole, and in Alaska, this might
include warming the soil, because at temperatures below freezing Pseudomonas work about as well as squirt guns.
Other bacterial boosts include adding oxygen to soil to stimulate the aerobic creatures, and mixing in waste water to
provide other nutrients."
AND...why?! is Silver the perfect exclusionary template to resist attack from the awful and smelly bacteria I hypothesis?? Well because of such properties as described below:
"Silver is a powerful, natural shield and antibiotic that has been used for thousands of years. Ancient Greeks lined their eating and drinking vessels with silver, as did many other cultures throughout the world. Pioneers of the American West would put a silver dollar in a jug of milk to keep it fresh without refrigeration. Did you ever wonder why silverware was made from silver? One of the properties of silver is that it kills bacteria on contact in six minutes or less. It may be that gold and silver were first used as valued currency because of their medical properties. In Biblical times, herdsmen would often “bury” ingots in their wells and fiercely defend this “sweet water”. "
But having bacteria make a Hologram is such a cool idea! From bacteria that exists, to genetically manipulated bacteria, to nanomachines..... HoloEVOLUTION at work. So, its disgusting..... someday it will be the state of the art nonetheless and you'll all say you heard about that ****, 10 years ago! You'll SEE! : )
It would make an interesting experiment but you may be the only person on this list that has the equipment to do it. God knows I'm not going to be handling e-coli in my kitchen or office any time soon.
Basement Bombers of the 60's, went to entrepreneurial garage operations in the 70's..... Many of us use the kitchen table to achieve our great works, but remember that Carlson (Xerox) invented his techniques by tying up the bathtub for months on end! (His wife had issues with this..of course). I say THIS project is less of a kitchen or office project, and more in line with Carlson's choice. But nonetheless, I considered this process because of a fantasy. MANY... people I've spoken to in life had the same fantasy... what if one were stranded away from standard resources.... could one still achieve what one wished. Sometimes its a trip into the medieval past, or sometimes its on a desert island.... its interesting to consider what it would take to make a solar oven, to bake sand into glass, to melt or draw coins, to make mirrors, to make rudimentary photographic products, to create a microwave strip down converter to signal one's presence to a satellite or off shore ship, to distill water, to water proof a hut or storage container, to create a refrigeration method, etc. etc. This bacteriological method of processing.... could turn your last year of desperate loneliness stranded on a barren desert isle... into a nifty show of Holographic snapshots at some Los Angeles Museum, to be viewed by thousands of grammar school kids, ....wondering what the heck their teacher wants them to write, in an after field trip report, about such a group of oddities, found packaged on that island, with your bones draped over their waterproof box, means to them...personally, especially after they see the scientific analysis placard, and read that the Holograms were developed with ****, as they all smiled at each other, and gave a collective.... YUCK...!!
YES, I think that is impetus enough to try such a grass roots technique, and so master its most delicate embouchure!
Have you tried not drying the film with a hair dryer. I just soak the film in a water/photoflo bath for about a minute and let it hang, if it's film, or lean it against a wall, if it's glass. A 4"x5" takes about an hour or two to dry. I know you're anxious to see the final result, but think of spending all day at work in the anticipation of coming home to a perfect hologram in the evening! Of course, you could hang it in the ceiling of your car and let the wind dry it. Then you may be the envy of your colleagues as you walk into the office with your hologram, but you'll probably get bloody strange looks from other motorists when they see bits of plastic dangling from your car ceiling!
Yes, I tried that test this morning and it's still ongoing.
I've got one deep red hologram that was treated to an alcohol bath and air dried and another yellow-green that was treated to a simple photo-flo distilled water spritz & squeegee after the post-bleach rinse.
I've got a "before" digital pic that I'll use to compare with an "after" that I'll take later today.
It looks like it's not the acetic acid. I exposed a sheet of film this morning and cut it in half so that I could test slightly differing dev times as well as removal of the acetic acid bath.
It looks like it's not the acetic acid that causing or encouraging the ongoing shrinkage. After 10 hours the two halves are still the same color.
Ok, I bagged up a hologram with a hygrometer and some dessicant for 24 hours and according to the hygrometer the humidity never went below 47%. I also didn't notice much of a color shift either (there was a little though).
The acetic acid bath seems safe enough as far as color shifting goes. Two holograms that were processed the same except for leaving that bath out on one, result in holograms of equal quality and color.
I've been focused on making a piece worthy of consignment and now that I have that (and hope to have a sale soon) I can focus on what's happening with the color.
A few experiments to do...
1) Change out the photo-flo for baby shampoo.
2) Try a 25% alcohol bath before moving on to 50 & 100%
3) ... ? (profit!)
What's come in mind is that for MBDCG with TMG (see recipe of Jeff Blyth), we need to keep plates in 60% RH environment, so we can use Sodium Nitrite (probably not Ammonium Nitrate because ammonium can maybe diffuse in DCG)
I notice that they don't understand the mechanism of 'crust' formation either. Having thought a little about it I was wondering if the alcohol somehow polymerised using the water molecules to form long chains?
In any case, I was about to suggest that you might try a final warm alcohol bath, say about 20 secs in alcohol at about 50 - 60 deg F (if you do try this, watch the temp doesn't go above about 80. The flash point of alcohol - the point where the fumes start combusting - is about 80). If this does break up the surface, by controlling temp and/or time it might be a sensitive color control mechanism.
"I notice that they don't understand the mechanism of 'crust' formation either. Having
thought a little about it I was wondering if the alcohol somehow polymerised using the
water molecules to form long chains?"
I have also been wondering about that curious drying behavior for quite a while. Sergey
Vorobyov described it already in SPIE 3358 (Sixth Int. Symposium on Display
Holography), p. 69:
"For Russian photoplates we have used drying by ethanol. The plate is consecutively dipped
in baths containing 50%, 80% and 100% ethanol for 1-2 mins and constantly agitated.
However, this process by itself does not give stable results.
The analysis of the drying process shows that only complete and homogeneous removal of the
water from the surface of the emulsion layer guarantees a high quality of the final
hologram. The presence of water inside of the emulsion layer does not influence the
uniformity of the hologram. However a thin layer of surface water is separated with large
effort from the surface and frequently remains even after processing in 100% ethanol.
Consequently coloured stripes and spots appear on the hologram."
Maybe the huge wavelength shift towards the IR we encountered on PFG-03 (when we were carrying out our SHSG tests) relates to that "drying problem".
Its always seemed straight forward to me.... dehydrating the surface, closes the pores, locking in moisture.... I do the same thing with 'witch hazel' (14% isopropyl) on my face, following shaving.
Of course as all astute shavers recognize, it also toughens up the follicles and dries out the skin... but careful examination notes, that surface hairs twist and one gets a regional twitchy feel on one's skin! And so do the long chains of protein, twist and mesh, so further strangulating the osmosis of fluids to the surface and impeding the penetration of even higher concentrations of alcohol. With thick (hard) emulsions, I heat the black of the glass while hanging the emulsion upside down at an angle, and then when I see the Hologram scatter slightly in red.... I then dip it and go from there.... slowly lowering it into my bathes. Warm alcohol to match the warm glass assures less distortion. I've also brought the color to where I wanted it (plus maybe 5-10 nm) and then shoved the glass emulsion into boiling alcohol! to freeze it 5-10 nm lower. Some scream STRESS! at me, I say.... try it. lol
> Maybe the huge wavelength shift towards the IR we encountered on PFG-03 (when we were carrying out our SHSG tests) relates to that "drying problem".
Re: Lower it into Boiling Oil! lol (I mean alcohol).
August 14 2003, 8:13 PM
"Of course as all astute shavers recognize, it also toughens up the follicles and dries out the skin... but careful examination notes, that surface hairs twist and one gets a regional twitchy feel on one's skin! And so do the long chains of protein, twist and mesh, so further strangulating the osmosis of fluids to the surface and impeding the penetration of even higher concentrations of alcohol."
Subsequent to alcohol dehydration, the emulsion looks like turned inside-out: its surface is mainly constituted by hydrophobic compounds.
"With thick (hard) emulsions, I heat the black of the glass while hanging the emulsion upside down at an angle, and then when I see the Hologram scatter slightly in red.... I then dip it and go from there.... slowly lowering it into my bathes. Warm alcohol to match the warm glass assures less distortion. I've also brought the color to where I wanted it (plus maybe 5-10 nm) and then shoved the glass emulsion into boiling alcohol! to freeze it 5-10 nm lower. Some scream STRESS! at me, I say.... try it. lol"
I would only scream CAUTION - due to the fire hazard. Otherwise, the use of hot alcohol baths has some tradition in DCG/SHSG technology.
> Maybe the huge wavelength shift towards the IR we encountered on PFG-03 (when we were carrying out our SHSG tests) relates to that "drying problem".
You 'froze it' where it stood."
Sure. The difficulty is to explain the action of different alcohols. Methanol for example, is said to cause a smaller wavelength shift...
Re: Re: Re: Lower it into Boiling Oil! lol (I mean alcohol).
August 15 2003, 3:29 AM
It is well-known gelatin being a very incoherent complex stuff, consists of a heterogeneous mixture of hydrolysis products of collagen. So the "compounds" refer to different amino acids that form polypeptide chains. The most important amino acids are: glycine, proline and hydroxyproline. Incidentally, I learnt there was one explicitly hydrophobic amino acid: phenylalanine.
Speaking of the geometrical form of the polypeptide chain Zelikman/Levi ("Making and coating of photographic emulsions", Focal Press London/New York 1964, p. 41) point out:
"The geometrical form of the polypeptide chain may be represented by an extended zigzag line with alternating side chains pointing in different directions (hydrophobic side chains lie predominantly on one side of the plane of the polypeptide chain and hydrophilic side chains on the other). (...) From 25 to 50% of all the side chains consist entirely of hydrocarbon groups and are distinctly hydrophobic. The remaining side chains, also hydrophobic in character, partially contain polar groups. Apart from glycine, where the radical is hydrogen, about one half of the total number of amino-acid groups in gelatin contain non-polar hydrocarbon groups whereas the rest have polar radicals."
Frankly, I ignore if this plays into the problems of "alcohol dried" gelatin layers. I simply never quite found an explanation what happens when a wet gelatin layer is "dried" by alcohol. All I know is there must be some difference between "air dried" and "alcohol dried" layers . The observation that it takes much longer to wet (with water) an "alcohol dried" layer seems to stress that. How come?
Re: Re: Re: Re: Lower it into Boiling Oil! lol (I mean alcohol).
August 15 2003, 6:55 AM
Okay, I knew all of that of course but..... this,
> "The geometrical form of the polypeptide chain may be represented by an extended zigzag line with alternating side chains pointing in different directions (hydrophobic side chains lie predominantly on one side of the plane of the polypeptide chain and hydrophilic side chains on the other).
I had not read or heard of.... I am investigating furthur. Thanks.
Re: Re: Re: Re: Lower it into Boiling Oil! lol (I mean alcohol).
August 15 2003, 8:10 AM
Could the hydrophobic side chains 'bend around' and couple with the hydrophyllic side chains to create a sort of 'gelatin cylinder'? Actually the idea is too crazy, even for me!
I was further thinking of the polymerisation of alcohol. Could the gelatin be cross linking with the alcohol acting as a catalyst? Then the different forms of alcohol may create different amounts of polymerisation and so different densities of 'crust'.
> Could the hydrophobic side chains 'bend around' and couple with the hydrophyllic side chains to create a sort of 'gelatin cylinder'?
Kind of like mobius micro tubes? I don't think so. But the isopropyl may contribute HO- (hydroxyl) segments which complete the chains and thus make the edge pretty fully hydrophobic??... or thus, sealed.
> I was further thinking of the polymerization of alcohol. Could the gelatin be cross linking with the alcohol acting as a catalyst? Then the different forms of alcohol may create different amounts of polymerization and so different densities of 'crust'.
Not cross linking in the standard way... but the surface tension of PURE methyl alcohol (dynes/cm) is lower then ethyl, or iso. (lowest of the three) alcohol UNTIL water is mixed with it... then it gains in molecular immobility, reversing the order, when in contact with gelatin, ...as the increased tension, forces water to homopolar status thus forcing it to 'bridge' the interfaces of the gelatin pores (gelatin = 8.3 dyes/cm) so shrinking the effective conduits for water to pass. At the same time, as we all know,gelatin is 'expanded' by water and ....dehydrated by alcohol, which shrinks the pore spacing directly. Drainage then, is an issue of consequence.
A 'wetting agent' would discharge the surface energy, by relaxing the bridging angles, and open the conduits...but then, so would the addition of most any of the myrid members of gelatin's reactive functional group. Unfiltered water is a great way to experiment with these, but expect no predictability.... lol
Deterministically, the process of drainage might benefit by the addition of an anti hardening agent such as Peptain enzyme, a drop or two of surfacant, and a drop or two of a commercial antistatic compound such as POLYACRYLAMIDE HYDROXYPROPYLTRIMONIUM CHLORIDE, which is used widely in the pharmaceuticals industry along with its viscosity controlling agent...gelatin! ( I figure, if she thinks its good enough to kiss it on her lips...its probably good enough to drain your Holographic emulsions with...know what I mean? )
I don't think either there is crosslinking involved here - since the process does not look like being irreversible.
"...but the surface tension of PURE methyl alcohol (dynes/cm) is lower then ethyl, or iso. (lowest of the three) alcohol UNTIL water is mixed with it... then it gains in molecular immobility, reversing the order, when in contact with gelatin, ...as the increased tension, forces water to homopolar status thus forcing it to 'bridge' the interfaces of the gelatin pores (gelatin = 8.3 dyes/cm) so shrinking the effective conduits for water to pass. At the same time, as we all know,gelatin is 'expanded' by water and ....dehydrated by alcohol, which shrinks the pore spacing directly. Drainage then, is an issue of consequence."
I meanwhile recall one of the Cambridge group's (Jeff Blyth) papers about holographic alcohol sensors. If I am not misled, they somewhere state that pure methanol actually fully penetrates a gelatin layer. They showed that methanol had a greater capacity to leave the gelatin swollen than isopropanol or ethanol.
> meanwhile recall one of the Cambridge group's (Jeff Blyth) papers about holographic alcohol sensors. If I am not misled, they somewhere state that pure methanol actually fully penetrates a gelatin layer. They showed that methanol had a greater capacity to leave the gelatin swollen than isopropanol or ethanol.
As the % purity of methanol goes up, its surface tension drops ...... I figured a static bath with increasing local water dilution... thereby raising the tension over a short time, but with a fresh stream of methanol flowing by, that pretty well negates that predilection. Higher temps. also increase mobility.
What did you think about the use of the cosmetic industry 'anti-static' compound?
Also, what about a dilute Histamine (an amino acid derivative formed by decarboxylation of histidine.) bath, to dilate the gelatin and increase mean water permeability.
"What did you think about the use of the cosmetic industry 'anti-static' compound?"
Yes, that's something we also had looked into (actually, there are many parallels between cosmetic and photographic ingredients) - particularly the use of quaternary ammonium salts. They can be found in shampoos and in most silver halide emulsions. At larger quantities they seem to affect the swelling behavior of gelatin.
"Also, what about a dilute Histamine (an amino acid derivative formed by decarboxylation of histidine.) bath, to dilate the gelatin and increase mean water permeability."
I do not know much about Histamine but I am aware of the effect of certain enzymes like trypsine on gelatin.
if I prepair my glassplate by protonizing the surface first, bevor coating the gelatinelayer on it, the gelatinelayer comes on it with the prehardener Cr3salt. The thikness is controled and fixed to not more, not less than 2 microns on the glas. When the layer is dry, it coms in a minute bath of formaline (1% in H20. then dry. This methode give stable results in gelatinelayer compliance. I think about the diffiusion constant of a layer say 30 microns to such of 2 microns. The 2 micronlayer would be much faster and easely saturated. This serves a uniformely chemical movement in thinn layer. Compared this fact to a 30 micron thik one, the thik layer will be nonuniform and irregularely served by the used chemicals?
Diffraction is also better served by the thinner layer.
"if I prepair my glassplate by protonizing the surface first, bevor coating the gelatinelayer on it, the gelatinelayer comes on it with the prehardener Cr3salt. The thikness is controled and fixed to not more, not less than 2 microns on the glas. When the layer is dry, it coms in a minute bath of formaline (1% in H20. then dry. This methode give stable results in gelatinelayer compliance. I think about the diffiusion constant of a layer say 30 microns to such of 2 microns. The 2 micronlayer would be much faster and easely saturated. This serves a uniformely chemical movement in thinn layer. Compared this fact to a 30 micron thik one, the thik layer will be nonuniform and irregularely served by the used chemicals?
Diffraction is also better served by the thinner layer."
That's for DCG, I suppose.
Apropos, nice to hear from you again, Horst (it took some 20 years - and the Internet to make it happen again! Are you still listening to the (electronically) translated cries of the bats in Casta...? Send me a mail (martinm "AT" SoftHome.net).
