Dip-N-Shoot DCG film plates.

jeff-blyth · Post by **jeff-blyth** » Sun Mar 14, 2010 2:37 pm

manalokos wrote:Hello Tony

The two spots are some kind of dirt or faint crystallization on the emulsion
that gave a bit of a different color, but they are as bright as the other parts I believe...

I'll be making some more plates tonight, I still have to get a hold on mold coating,
and to be able to put more dichromate into the gelatin to lower exposure times I'll follow uncle Dave's advice.

It seems that AmDi is more soluble in water than Kdi:

units of solubility in g/100g H2O at 20ºC

Ammonium dichromate = 35.6
Potassium dichromate = 12.3
Sodium dichromate = 183

See here:
http://en.wikipedia.org/wiki/Solubility_table

And even more, the sodium dichromate seems super soluble in water, would it have the same behaviour
as the Kdi and Amdi so it would be suitable for holography with a great increase in sensibility?
Has anyone tried it?

Best regards
Filipe

Hi Filipe,
We went over this ground 3 years ago here:
http://www.holographyforum.org/phpBB2/v ... 2&start=15

(2nd page of thread)
Jeff

manalokos · Post by **manalokos** » Mon Mar 15, 2010 1:38 am

Hello Jeff!

That is great!
What is your opinion? Is it better than Kdi?
Is the possibility of making a higher concentration solution
resulting in increased sensibility or not at all?

Thanks

Best regards
Filipe

jeff-blyth · Post by **jeff-blyth** » Mon Mar 15, 2010 12:52 pm

Which dichromate?
Dave’s (as usual) very practical answer for making do with what most folks here already have available seems good to me as a means of packing in as much AmDi as possible without crystallization. I specifically used KDi for the “G307” process for 532nm lasers because it required a baking step at 100C or so and that caused some ammonia gas to come off AmDi leaving some ferociously reactive chromic acid and that caused problems (violet to black holograms). Were you to want to order a fresh supply of dichromate then I would try going for a reasonably good grade (low heavy metal impurities) of sodium dichromate because you can then really pack that stuff in without crystallization occurring.
However this is all if you have 532nm line, otherwise for short wavelengths like say the increasingly available 405nm LD you have a hugely greater absorption and you therefore need to cut the dichromate concentration right down hugely or no light will come back from your object, (but the photosensitivity with 405nm can approach AgBr levels!).
Jeff

manalokos · Post by **manalokos** » Mon Mar 15, 2010 1:47 pm

Thanks for the reply Jeff,

I ordered 200g of NaDi and 100 of AmDi to test... I don't know the purity
of the product, but I believe neither does the seller!

Yes, the sodium might be great for super concentrations without crystallization!
I always have trouble with crystals, yesterday I tried a very quick soapy water bath
after the KDi dip, it stopped most of the crystals, but gave some unevenness to the gelatin coating...

Why do you guys call "G307" to that process? It is a quite fancy name!

Best regards
Filipe

jeff-blyth · Post by **jeff-blyth** » Mon Mar 15, 2010 3:28 pm

manalokos wrote:Thanks for the reply Jeff,

I ordered 200g of NaDi and 100 of AmDi to test... I don't know the purity
of the product, but I believe neither does the seller!

Yes, the sodium might be great for super concentrations without crystallization!
I always have trouble with crystals, yesterday I tried a very quick soapy water bath
after the KDi dip, it stopped most of the crystals, but gave some unevenness to the gelatin coating...

Why do you guys call "G307" to that process? It is a quite fancy name!

Best regards
Filipe

I was working on a paper for the 7th International Symposium on Display Holography 2006. My "lab book" is just Excel files. The formula starting on line 307
was coated and formulation details were sent over the pond to John Pecora to run his tests on. I think he chose to refer to it by this line number with G for gelatin.
We need a short name for everything and it is more specific than say "Witches' brew No. 14".
jeff

manalokos · Post by **manalokos** » Wed Mar 17, 2010 2:03 am

Hello!

Just ended my session today,
in my dark box I have some plates coated with double thickness gel
dipped in Kdi, very yellow, I've had a lot of problems with these!
They peel of if they receive heat from my finger while holding them,
maybe because the glass expands and the gel does not, or some more complicated reaction,
anyway I've been very frustrated with the results, milkyness is the word, even with
5 minutes UV light hardening, saturated alum solution hardening...etc.

I also had a faint yellow plate that had a "plastic scotch tape thickness" gelatin
and was there waiting to be forgotten, as it was many many days old...
I was getting dim results with the thick very yellow plates, to I tried this one with 15 minute
exposure... if I was getting dim holos because of the lack of laser power, this one would be even fainter,
but no, it was bright and clear! So I guess it doesn't matter much the yellowness of the plate alone,
but the ratio between yellowness and thickness, or the amount of Kdi for the ammount of gel...

Here are the results of this week:

Seashels 6x6cm. thick emulsion (this one was not so bad!):

: hhhh3.jpg (125.2 KiB) Viewed 2333 times

My girlfriend's picture, silver print on pebble, 6x6cm.:

: hhhh4.jpg (152.88 KiB) Viewed 2333 times

And the movie and picture of the big 14x10cm gears from an old clock.
I noticed that the hologram has a blue ghost copy, what could be doing this? (check the movie)

: hhhh1.jpg (123.71 KiB) Viewed 2333 times

: hhhh2.jpg (161.5 KiB) Viewed 2333 times

Next plates will be with quite thin coatings!

jeff-blyth wrote:
manalokos wrote:We need a short name for everything and it is more specific than say "Witches' brew No. 14".
jeff

Thanks for the answer Jeff, it is always nice to know the origin of the name!

Best regards
Filipe

JohnFP · Post by **JohnFP** » Wed Mar 17, 2010 12:57 pm

To be honest, I am a little confused by the suggestion of putting as much AmDi in the plate as you can for a bright SBR hologram in DCG. Optimally for SBR you want about a reading 50:50 ratio of object to reference lighting (not the actual ratio as I will explain). This is because the object diffuses the light and randomly polarizes the light. Diffusion obviously nets a light loss and the random polarizion only allows parts of the object that are reflect the same polarization to interfere with the reference beam. Of course, if the polarization of the object is only off by a few degrees, then some interference will occure all the way to a polarization off the object that is 90 Degrees rotated from the polarization of the reference that will not interfere at all. So loosely saying 100% interfereing falling off to 0% interfering nets about 50% interfering. Diffusion cuts it down more. And now the strong yellow provides even less light. Not to mention if you are off brewster a little even more loss. Reflections are best at about 2:1 - 4:1 (actual, not reading) I have found for DCG. If you elliminate the deep yellow altogether, you are probably already at 4:1 depending on object. So I would suggest cutting way back on the amount of AmDi and use a longer exposure if you are not having movement problems for brighter holograms. Seems like your already at long exposures.
Anyway, just a suggestion.
Peace.

dave battin · Post by **dave battin** » Wed Mar 17, 2010 2:53 pm

I'm not sure i understand what you are trying to say above John, could you simplify your answer a bit? when shooting in the green region the amount of light that goes thru the plate is way less than you are use to when you shoot dcg holograms in the blue region.

Felipe is doing a good job as we can see in his photos and all i know from a green point of view(30mw @532nm), you need as much Dichromate as possible to achieve the shortest exposure times ..............as he’s doing 15 minuet exposures now. :wall:

dave battin · Post by **dave battin** » Wed Mar 17, 2010 5:08 pm

opps sorry, this is what i meant to say

dave battin wrote:I'm not sure i understand what you are trying to say above John, could you simplify your answer a bit? when shooting in the green region the amount of light that goes thru the plate is way more than you are use to when shooting in the blue region.

Felipe is doing a good job as we can see in his photos and all i know from a green point of view(30mw @532nm), you need as much Dichromate as possible to achieve the shortest exposure times ..............as he’s doing 15 minuet exposures now. :wall:

JohnFP · Post by **JohnFP** » Wed Mar 17, 2010 6:01 pm

Dave, I shot in 514 as much as I shot in 488, did you forget? I did a lot of research in all wavelengths an Argon Ion could produce. Please feel free to visit my website look at color test, wavelenght tests, etc. 532 is not that far off from 514.

I agree that if you want to keep your exposure to a minimum that, sure load the plate with AmDi. But he is having crystalization problems and is going to give up more of the optimal light ratio for a bright SBR.

But, here is what I was trying to say, simply, I hope...

For the brightest SBR hologram in DCG, we want try to keep the effective light level ratios around 4:1 (ref:obj). Lower ratio and you get noise, higher ratio and you lose brightness.

I was pointing out that if Filipe is not having movement problems, he may not need to increase AmDi, but rather increase exposure time a little bit. But I will stay quiet as he is doing quite well.

Excellent job Filipe, seriously.