Milkyness in dcg

Dichromated Gelatin.
Tony DCG
Posts: 147
Joined: Thu Jan 08, 2015 1:47 pm

Milkyness in dcg

Post by Tony DCG » Thu Feb 21, 2013 11:43 am

Tony DCG wrote:milan what gelitan are you using again?
A while ago I tryed some 190 bloom strength hoping for some better broadband results but no matter what I did I would get whitening.
holomaker wrote:And, my last batch of the plates are with too thick emulsion and too much dichromate in it (100:12:3), so for recording at 450 nm, often I am getting terrible UV shifting (I can't say blue shifting, because laser is already blue). Tried to skip 70% alcohol bath in order to get broadband reflection hologram, but what I got is just whole plate broadband, while object is really not visible.
Sounds like you have a lot of issues you need to sort out. IMO I would reccomend a systematic approuch. Examples:
If you are unsure about coating thickness, try a veil coating, apply as normal but allow it to sit vertical for say 1 minute. This will give you a thinner coating on top and thick one the bottom. Cut film into strips horizantally so you can have a good sample of thicknesses. Looking at your ratios 100:12:3 you should be fine. In fact for BB you could go up to 6 AmDi.

You can the mask your laser light using a cardboard card and vary your exposure time. Go big something like your nominal time (say 1 minute). Try 30 seconds, 1 minutes, 2 minutes, 3 minutes.

Then with either with light fixing or with chemicals exposure you can vary fix time ie mask a third of the plate, light fix it, the exposure the next third (along with the first third) etc. This will bracket your fix time.

Lastly you can vary your IPA %s as well if you wish.

As far as environment, invest in a cheap humidifier. Try to acheive 40-50% RH and stay around 70-75'F in room temperature. Try to eliminate that variable. This is for coating and shooting.

This can be done with one (maybe 2) large 11"x9"" plate and should get you in the ballpark as far as parameters. It would be great to publish these results to the forum and allow us to verify you are getting expect results.

I think every DCG newie should go though this process. Then make good notes, seal the plates and use it as you change your process.
Just my thoughts :)
Good luck!!

MilanKarakas

Milkyness in dcg

Post by MilanKarakas » Thu Feb 21, 2013 8:56 pm

Tony DCG wrote:milan what gelitan are you using again?
A while ago I tryed some 190 bloom strength hoping for some better broadband results but no matter what I did I would get whitening.
Seems that both of my gelatin type has its own problems: Dr.Oetker, when in cold water almost instantly dissolves, or at least it looks like that. And I had a lot of problem with this type with mold coating. Another type is Podravka's Dolcela, of unknown Bloom. It has different appearance in cold water, for example; 12 grams in 100 ml of water swell so that whole thing does not move. After temperature reaches about 30C, then it become more liquid, and at about 35C completely dissolves. Then I slowly increase temperature to 45C and mix there for a long period.

Out there are two contradictory informations, where one source says "mixing at least 45 minutes", while other source said opposite: "as short as possible". I don't know what is the truth.

Last time I mixed it very slowly, over 3 hours. Then added KDi (I have not AmDi), and continues to mix another 30 minutes or so. Then keeping 45C, while preparing plates at 38C. Then moving double boiler inside laminar flow hood and adjust boiler temperature to 38C and then filtering in applicator bottle, maintaining this new temperature. After pouring liquid over the plate, moving plate up so that I have room for next one. Noticed that no matter how well pre-heat plate at 38C or bit more, it cools so quickly. Veil solidify even before it reaches bottom. If I do it quickly, then somehow I am able to manage good coating.

After wiping off most of the liquid, plate stays there (above the rest), while excess liquid is filtered and slowly filtered back in the applicator bottle. Often I have just enough room for applying to two 20x40 cm plates. Remaining liquid is then kept in aluminum foil and refrigerated at about 3-5C for next use.

I noticed that next time, whole thing did not dissolve at 35C, but more close to 40C or so. Still, I am not overheating over 45C as many documents recommending.
Tony DCG wrote:
MilanKarakas wrote:And, my last batch of the plates are with too thick emulsion and too much dichromate in it (100:12:3), so for recording at 450 nm, often I am getting terrible UV shifting (I can't say blue shifting, because laser is already blue). Tried to skip 70% alcohol bath in order to get broadband reflection hologram, but what I got is just whole plate broadband, while object is really not visible.
Sounds like you have a lot of issues you need to sort out. IMO I would reccomend a systematic approuch. Examples:
If you are unsure about coating thickness, try a veil coating, apply as normal but allow it to sit vertical for say 1 minute. This will give you a thinner coating on top and thick one the bottom. Cut film into strips horizantally so you can have a good sample of thicknesses. Looking at your ratios 100:12:3 you should be fine. In fact for BB you could go up to 6 AmDi.
I think first issue can be solved as Dave Battin recommended: to heat whole plate (with hair drier) for a while until dense and very viscous bottom part of the plate goes more down. Seems that it gels in just few seconds after application. There are two reasons: temperature of the glass plate drops by itself too quickly, and by fast evaporation rate of the liquid gelatin/KDi mixture (in connection with dry air). Waiting of 1 minute can't help if there is already gelled film.

In the past, once I tried heat mixture up to 70C, but then got different set of problems. And it dries even faster than from 45C (also connected with low humidity).
Tony DCG wrote:You can the mask your laser light and vary your exposure time. Go big something like your nominal time (say 1 minute). Try 30 seconds, 1 minutes, 2 minutes, 3 minutes.
Right now, my setup is made so that I am shooting transmission holograms. I feel that it is less prone to blue shifting problem. At least object is visible at various exposure time. When shooting deep scene with too long exposure, it happens that very deep part of the scene is visible, while bright and close object is completely invisible (for reflection hologram).:

http://www.flickr.com/photos/milan_kara ... hotostream

Here is visible only package of C vitamin, while figure in the front looks completely dark. It is good sign of the overexposure. I am not sure in beam ratio, but when measuring what come to the plate from the reference beam, I am trying to get the same reading of light what come from the object. Maybe I did not understand it well, or object beam should be equal, 1/2 of that of reference beam, or something else?

And, instead blocking part of the plate (which is hard for transmission hologram without disturbing everything), I rather shoot many small cut plates with various times. And, seems that I have still problem with coherence stability with this blue laser; sometimes the same exposure, one plate looks okay, while another with lack of depth, or lack of complete scene.

Tried also SBR, but whole time then should be reduced dramatically, since lot of light cause terrible UV shifting. Only where beam is weaker, this part is somewhat visible, and mostly milky.
Tony DCG wrote:
Then with either with light fixing or with chemicals exposure you can vary fix time ie mask a third of the plate, light fix it, the exposure the next third (along with the first third) etc. This will bracket your fix time.

Lastly you can vary your IPA %s as well if you wish.

As far as environment, invest in a cheap humidifier. Try to acheive 40-50% RH and stay around 70-75'F in room temperature. Try to eliminate that variable. This is for coating and shooting.

This can be done with one (maybe 2) large 11"x9"" plate and should get you in the ballpark as far as parameters. It would be great to publish these results to the forum and allow us to verify you are getting expect results.

I think every DCG newie should go though this process. Then make good notes, seal the plates and use it as you change your process.
Just my thoughts :)
Good luck!!
Yes. I think last time I changed too much variables at once. Few attempts to make mold coating completely failed due to too rough surface. Probably after all, this "Nigrin, NanoTec" is not proper surfactant, or I do some other mistake. Then I decide to do simple veil coat, which looks promising at first. I will stay at veil coat, but will try to do something different about humidity and temperature.

All of that should wait few days until my flu gone. Now I feel still weak and have high body temperature.

Thank you for your advice, I will let you know how it goes when will do next batch of the plates.

Best--
milan

Johnfp

Milkyness in dcg

Post by Johnfp » Fri Feb 22, 2013 9:15 am

I read this twice but I have ask, what type of fixing are you using post exposure, just light fixing?

MilanKarakas

Milkyness in dcg

Post by MilanKarakas » Fri Feb 22, 2013 9:51 am

Johnfp wrote:I read this twice but I have ask, what type of fixing are you using post exposure, just light fixing?
No. I tried, but it not working good to me. So far, the best is heat fixing. Baking for 2-4 minutes at 100C. This gives me clear emulsion, but if baked too hot or too long, then no hologram on it.

Edit: I tried light fixing with 40W spot halogen lamp, with steps of 15 seconds and partially covered plate. The best hardening is at about 90 seconds, but got somewhat washed out hologram (not good DE). Then tried light fixing at opposite side of the hologram (emulsion side), bit different result. Then tried both side. No matter how long light hardening, some milkiness remains, but too much light hardening also cause disappearing of the hologram. Probably into the UV spectra.

Best--
milan

Tony DCG
Posts: 147
Joined: Thu Jan 08, 2015 1:47 pm

Milkyness in dcg

Post by Tony DCG » Fri Feb 22, 2013 10:53 am

Thanks milan on your progress. It is great to see some DCG post and your passion is in the right place.

There are many layers to your situation and will be tough to get you on track without a level of control. Basicly meaning if this was Martha Stewart's cake baking forum (might have more followers ;) ) and you said "well I don't have white wheat flour but rye flour, I'm not using sugar but I do have honey and the eggs I use are that from a platypus", I think it would be tough to make that cake palatable.

Your gel mix time is OK. I'm from the school of shorter is better, mix no more than 20 minutes although you would only see suble changes if you go longer. If your gel solidifies before it hit bottom and your glass is warm then there is something really odd about your gel. This should never happen and I have tryed Bloom Strengths of 190 to 290 and never saw that problem. Make sure that the plate is laying lenght wise meaning the 20cm is vertical and the 40cm is horizonal.

John, if your out there, have you worked with KDi? That might be a whole new ball game as it pretains to crosslinking. Since it is not as sensitive as AmDi your exposure time, fix time and post processing might be very different than AmDi. I am not sure what your exposure times are nor what laser you are using, although I think you need green to red wavelengths (right?). Whitening is also a function of no or low crosslinking.

milan, if possible try to look at John's recipe either on his web site or in holowiki. See what is different and if you like let us know.
Also, if you need gelatin I would be happy to send you some. AmDi might not be possible but best to start somewhere. I don't mind sensing it overseas.

Best of luck to you!!

Johnfp

Milkyness in dcg

Post by Johnfp » Fri Feb 22, 2013 11:58 am

Milan
Can you get some Kodak Rapid Fixer?
Or some Sodium Metabisulfate and Alum?
I have much better and more consistant resulte with chemical hardening.

I am leaning hard toward your post exposure hardening process that is causing the milkiness.


-------------------------------------------------------------

Yes Tony, I have woked with KDi. I was told it is slightly more sensitive and better for broadband holograms (actually white). When I used it I never really noticed any difference to speak of.

I remember Jeff saying the AmDi release Amonium which KDi does not and this Amonium cause a PH change I think or a loss of "material" of the amonium itself evaporting. But like I said I seem to have used them both and could not tell a big difference.

Tony DCG
Posts: 147
Joined: Thu Jan 08, 2015 1:47 pm

Milkyness in dcg

Post by Tony DCG » Fri Feb 22, 2013 2:11 pm

Here is an old post from Kiffdino, if you can see if you can look this thread up, might offer some clues.

He had 220 bloom gel

http://holoforum.org/oldforum/viewtopic ... &start=120

Hey guys. Heres an update. Ive been doing lots and lots of testing. Changing pretty much all paremeters.

My Coatings are getting better and I have tried out various Gelatine concetrations.
I had the best results with 14g of Gelatin dissolved in 100ml of Water.
I obeserved that thicker gelatin layers can take higher Kdi concentrations, but the Holograms come out dimmer.
Still shooting green with my cohrent 315m, even though i had to turn the power down to 80% output power because for some reason the laser is unstable at full power.
The ready light at the analog controller goes of all the time an it never stabalizes, thats a new problem. Havent figured out why it does that.
Doing Vail Coating.
I coat first, put them in the fridge after 4 hours drying and sensetize the plates before I shoot.
Kdi Concentration @ 3.75g in 100ml of water.

So these are the last ones i made, everything at room temperature, except the laast alcohol baths is heated to about 30°C.

settle 13 min
Exposure 3 min
dark 5 min
chemical fix 1 min until all yellow gone
2 Waterbaths each 1 min
ISO standard, high diffraction in last bath
hairdryer 5 min
oven 10 min

The plate that has the blue II written in one corner has received an aditional light fixing after the dark reaction.
50 Watt halogen light at 80cm distance for 1 min.

On both plates, cristilization is visible. I didn't have these problems with the thicker coated plates. I'll try to fix that with more soap in the sensetization bath.

Your last comments havent been unnoticed. I tried changing the temperature of the washing bath on a test a week ago. But i didnt control the temperature closely. I just heated it until it felt warm.
The result was a VERY milky plate with enormous noise, hologram was barely visibly but the layer was extremely bright. Maybe if i find a way to fine tune the temperature in the water baths, i will achieve higher brightness levels.
AttachmentsP1010149x.jpg (22.1 KiB) Viewed 632 timesP1010133x.jpg (23.02 KiB) Viewed 632 times

MilanKarakas

Milkyness in dcg

Post by MilanKarakas » Fri Feb 22, 2013 8:20 pm

Tony DCG wrote:Thanks milan on your progress. It is great to see some DCG post and your passion is in the right place.
Thanks Tony. I am trying my best to get back on track after all that troubles with my laser(s). Now, I want to solve gelatin 'mystery'... and later will back to laser(s).
Tony DCG wrote:There are many layers to your situation and will be tough to get you on track without a level of control. Basicly meaning if this was Martha Stewart's cake baking forum (might have more followers ;) ) and you said "well I don't have white wheat flour but rye flour, I'm not using sugar but I do have honey and the eggs I use are that from a platypus", I think it would be tough to make that cake palatable.
Exactly it is how I started: first read many 'cook-books', then started my own way. This is because, as you said, sometimes can't follow exact recipe because of missing (or wrong) ingredients.
Tony DCG wrote:Your gel mix time is OK. I'm from the school of shorter is better, mix no more than 20 minutes although you would only see suble changes if you go longer. If your gel solidifies before it hit bottom and your glass is warm then there is something really odd about your gel. This should never happen and I have tryed Bloom Strengths of 190 to 290 and never saw that problem. Make sure that the plate is laying lenght wise meaning the 20cm is vertical and the 40cm is horizonal.
Next time I will cut that plate to half. I have old stock of 20x40 cm plates bought long time ago for capacitor purpose (Tesla coil). Fortunately, I did not use all of that plate on capacitors, so now I have plenty of glass for experimenting for a while.
Tony DCG wrote:John, if your out there, have you worked with KDi? That might be a whole new ball game as it pretains to crosslinking. Since it is not as sensitive as AmDi your exposure time, fix time and post processing might be very different than AmDi. I am not sure what your exposure times are nor what laser you are using, although I think you need green to red wavelengths (right?). Whitening is also a function of no or low crosslinking.
I think something is related in differences between KDi and AmDi, but that is not strictly and directly related to sensitivity, nor post-processing.

I asked my friend chemist what he think about possibility that gelatin with AmDi mixed in retain water more easily than KDi, and whether AmDi is more hygroscopic. He said that it is possible, but not sure. If so, then next scenario is possible: What if gelation time and way of gelation (refrigerating, or keeping in humid area) differ for that two chemicals mixed in? What if rapid drying of the surface with water/gelatin/KDi mix make 'impenetrable membrane' of partially or no cross-bonded chemicals that make collagen structure (helices and triple helices)? What if layer close to the glass somehow manage to 'renaturates', while the rest close to surface not? Something about that is mentioned the gelatin manual, which Joe Farina posted relatively recently in this topic:

http://holoforum.org/forum/viewtopic.ph ... =650#p5898

Direct link:

http://www.gelatin-gmia.com/images/GMIA ... l_2012.pdf

At page 8, there is few probably most important sentences:

"Gel Strength – The formation of thermoreversible gels in water is one of gelatin’s most important properties. When an aqueous solution of gelatin with a concentration greater than approximately 0.5% is cooled to approximately 35-40°C it first increases in viscosity, and then later forms a gel." (emphasis in bold text)

So, what I got is actually not yet a gel, but just mixture of amino acids with high viscosity, which resemble gel, but not even close. In the continuation, there is something also important:

"The rigidity or strength of the gel depends upon gelatin concentration, the intrinsic strength of the gelatin, pH, temperature, and the presence of any additives. The intrinsic strength of gelatin is a function of both structure and molecular mass."

That is maybe related of water concentration of gelatin vs. amount of dichromate. But, still that part did not yet get to the most important part, for which I am not sure how it works:

"The first step in gelation is the formation of locally ordered regions caused by the partial random return (renaturation) of gelatin to collagen-like helices (collagen fold)."

The first step! How long it takes to all of that amino acids to form collagen-like helices? What if some of amino acids are not cross-bonded, and got lose during last hot alcohol bath? My very last plate (before flu hit me hard) come out with thin coating on glass side after last alcohol bath. Something is for sure lost from the emulsion side during dehydration. I did not paid attention to that earlier, but I bet I saw that. This doesn't bothered me as long as hologram looks okay.

Does anyone else noticed such thin (and somewhat milky) coat after last alc. bath on the glass side of the plate? And if yes, does this plate (and few other before that one) come out milky?

One sentence skipped, and then the continuation:

"Hydrophobic, hydrogen, and electrostatic bonds may be involved in the crossbonding. Since these bonds are disrupted on heating, the gel is thermoreversible. Formation of the crossbonds is the slowest part of the process, so that under ideal conditions the strength of the gel increases with time as more crossbonds are formed. The total effect is a time-dependent increase in average molecular mass and in order (38,39)."

I think most important part is worth to 'paint' red. I think my last plates turns out milky because lack of time for such cross-bonding to happen. Note on next page of this manual that this holds for 6.67% of the gelatin!!!

What I do on my plates is initially 12% of the gelatin, BUT that percentage holds until water evaporates, mostly from the surface. As film dries, water as a 'transport' mechanism vanishes, partially cross-bonded amino acids remains, just 'sitting there' until dichromate attempting to cross-linking (and perhaps cross-bonding as well). Chemical, light and thermal hardening maybe helps dichromate to harden this part, but if just few weak bonds remains, it is also possible that such parts get lose and become lost in alcohol bath(s), and maybe later (during hot air drying) - distorting surface of the film even more (and not only at surface).
Tony DCG wrote:milan, if possible try to look at John's recipe either on his web site or in holowiki. See what is different and if you like let us know.
Also, if you need gelatin I would be happy to send you some. AmDi might not be possible but best to start somewhere. I don't mind sensing it overseas.

Best of luck to you!!
Everything is different in small quantities. From AmDi to KDi, to many other variations. Some subtle, almost unnoticed, some bit bigger. I think I will first pay attention on forming proper gel structure, and later on post-exposure fixing.

Best--

milan

MilanKarakas

Milkyness in dcg

Post by MilanKarakas » Fri Feb 22, 2013 9:21 pm

Johnfp wrote:Milan
Can you get some Kodak Rapid Fixer?
Not really. Tried few local sources, but did not found anything. On eBay, there is some offer for about $13, but shipping is overkill, over $500 from USA to Croatia! I think that in Europe maybe somewhere exist some supplier which is more close to me, but also afraid that price may be high for shipping.
Johnfp wrote:Or some Sodium Metabisulfate and Alum?
Yes, I have Sodium Metabisulfite, Potassium Metabisulfite (may I use this one instead first one?), and I have small amount of Potassium Alum (aside my own DIY alum, which is not properly neutralized with NaOH after aluminum is 'etched' in H2SO4).

Just need some recipe, or amounts: how much of each chemical to mix into water to get decent DIY hardener?

Johnfp wrote:I have much better and more consistant resulte with chemical hardening.
Lat time I tried one plate immersing in Sidium Metabisulfite, and it looks okay at first look, but lack of hologram (got just less milky plate, but something else was wrong, perhaps laser). Then made mistake and add very acid alum with lot of H2SO4, then whole thing begin to peel of the emulsion. Then gave up of further experimenting until get proper recipe. Maybe Sodium Metabisulfite alone suffice, I don't know.
Johnfp wrote:I am leaning hard toward your post exposure hardening process that is causing the milkiness.
I am not sure in anything. If so, then after really cold water of first bath (about 15C), plate is milky. Increasing temperature did not immediately make more milkiness, until some high temperature is reached (I think about 28C or so). My point is: at wide range of water bath temperature, milkiness is constant. Only baking gives me very clear plates, but then no hologram is visible (and I am pretty sure it did not goes into UV range).
Johnfp wrote:-------------------------------------------------------------

Yes Tony, I have woked with KDi. I was told it is slightly more sensitive and better for broadband holograms (actually white). When I used it I never really noticed any difference to speak of.

I remember Jeff saying the AmDi release Amonium which KDi does not and this Amonium cause a PH change I think or a loss of "material" of the amonium itself evaporting. But like I said I seem to have used them both and could not tell a big difference.
If I remember correctly about Jeff Blythe speach, he mentioned that issue about G307 formula, where baking procedure is essential for increasing sensitivity for green laser, and in connection with glycerine. Not sure how it will reflect if AmDi is used and hardened by baking at 100C (without glycerine in emulsion).

Best--
milan

MilanKarakas

Milkyness in dcg

Post by MilanKarakas » Fri Feb 22, 2013 9:38 pm

Tony DCG wrote:Here is an old post from Kiffdino, if you can see if you can look this thread up, might offer some clues.
Yes, thanks Tony. I think first clue is in way of preparing the plates. The main difference is that plates were in refrigerator for four hours. And after releasing mold, already cold plate did not loosing water so fast as is in the case with freshly coated hot plate (cca. 38C). I think I leaved plates for 30 minutes, but that suffice to gelatin to begin its job connecting all amino acids together, then continuing this job at relative higher humidity than now (at this time it was autumn).

In my previous post, I mentioned suspecting that gelatin alone should be 'in good health', or properly gelled - and that every other related issues maybe are secondary. I remember my first attempt to make G307 is somewhat better, without much milkiness, but at this time I had different set of problems (crystallization of the KDi after dip-n-shoot method), problem with my laser, and so on.

Next time I will try coat two big plates, one leaving in the kitchen cabinet, and another one put into refrigerator for some longer period (maybe 12 hours). After that, I can compare the results.
Tony DCG wrote: He had 220 bloom gel

http://holoforum.org/oldforum/viewtopic ... &start=120

Hey guys. Heres an update. Ive been doing lots and lots of testing. Changing pretty much all paremeters.

My Coatings are getting better and I have tried out various Gelatine concetrations.
I had the best results with 14g of Gelatin dissolved in 100ml of Water.
I obeserved that thicker gelatin layers can take higher Kdi concentrations, but the Holograms come out dimmer.
Still shooting green with my cohrent 315m, even though i had to turn the power down to 80% output power because for some reason the laser is unstable at full power.
The ready light at the analog controller goes of all the time an it never stabalizes, thats a new problem. Havent figured out why it does that.
Doing Vail Coating.
I coat first, put them in the fridge after 4 hours drying and sensetize the plates before I shoot.
Kdi Concentration @ 3.75g in 100ml of water.

So these are the last ones i made, everything at room temperature, except the laast alcohol baths is heated to about 30°C.

settle 13 min
Exposure 3 min
dark 5 min
chemical fix 1 min until all yellow gone
2 Waterbaths each 1 min
ISO standard, high diffraction in last bath
hairdryer 5 min
oven 10 min

The plate that has the blue II written in one corner has received an aditional light fixing after the dark reaction.
50 Watt halogen light at 80cm distance for 1 min.

On both plates, cristilization is visible. I didn't have these problems with the thicker coated plates. I'll try to fix that with more soap in the sensetization bath.

Your last comments havent been unnoticed. I tried changing the temperature of the washing bath on a test a week ago. But i didnt control the temperature closely. I just heated it until it felt warm.
The result was a VERY milky plate with enormous noise, hologram was barely visibly but the layer was extremely bright. Maybe if i find a way to fine tune the temperature in the water baths, i will achieve higher brightness levels.
AttachmentsP1010149x.jpg (22.1 KiB) Viewed 632 timesP1010133x.jpg (23.02 KiB) Viewed 632 times
Yes, it differ from my last batch of the plates, and way of preparation in many details. I hope soon solve 'the mystery' of milky plates all the time...

Best--
milan

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