Milkyness in dcg

Dichromated Gelatin.
Dinesh

Milkyness in dcg

Post by Dinesh » Fri Mar 01, 2013 2:02 pm

No worries! Please continue with Milan's problem. Sorry to interrupt.

MilanKarakas

Milkyness in dcg

Post by MilanKarakas » Fri Mar 01, 2013 3:38 pm

Tony DCG wrote:
MilanKarakas wrote:I just wanted to be sure that there is no condensation on upper surface, while humidity is pretty high (over 85% measured). As temperature goes down, humidity will goes dow slowly as well.
I would be surprised if this works. That is some very high humdity. I'm not sure what you wish to accomplish in trying this but it could be interesting.
This is not my idea. I read next document:

DCG Masters for Single Beam Photopolymer Copies
Richard D. Rallison

Where at page 2 he said next:

"To make master quality film for reflection masters mix an 8-30-350 formula as per instructions in reference 1 and let it get old and hard before using it. In my lab the film becomes hard enough from dark reaction in about 1 week. We work at about 75 degrees F (24C) and 55% RH. The hardening can be reduced to 4 hours if done at 150 degrees F (66C) in nearly saturated circulating air. Some experimenting with time and conditions is suggested to determine the best hardness for your lab. The ageing dramatically reduces the bulk scatter noise produced by processing in hot alcohol. The film is hard enough when bulk scatter disappears and is to hard when only a weak image is produced with 100 mj/cm*cm at 488 nm."

Tony DCG wrote:If you look at the great centers of DCG like Utah, New Mexico (USA) where they mass produce DCG, the humidity is very low. This can be argued of coarse but I think ideally you want low RH to dry film. Now if you wish to have your film more sensitive meaning less exposure time, then you can shoot in high temperature and high humidity. I've have heard theroies as to why that is but basiclly it comes down to control. Film stores longer in a low RH low temp environment. Anyway, no matter. It is great you are trying things out. You will adopt your own ideas based on experiements and in the end you will be better for it.
No, sensitivity is not an issue at the moment, but yes you are right (article about storage time, and about sensitivity):

Notes for tutorial IV:

DCG and other non-silver holographic materials,
Richard D. Rallison, Ph.D.


"Storage after coating - DCG stores well at low humidity in a refrigerator or freezer but containers must prevent contaminaton, condensation, freezer burn and frost which can all destroy surface quality. Firm of 10 to 20 microns or more store best and are good for at least a year. At room temperature and 50% RH, thin films are good for few hours, thick films typically last a week or more. The addition of a small quantity of TMG to the mixtrue will greatly increase storage time at room temperature by increasing the pH."

And, then:

"Esposure characteristics - DCG is most sensitive in a hot and moist environment. At 50% RH and 68 degrees F (20C) it may require 60 mj/cm^2 fo 488 nm light, while at 75% and 80F (27C) 4 mj/cm^2 will do the same job. At 441 nm less than 1 mj is enough and at 514 or 532, 50 to 100 may be necessary. The percentage of dichromate affects speed more or less lineary, a 25% mixture is typical but mixtures of from 10 to 30 percent are necessary to control color. Gross overexposure will cause a decrease in efficiency all the way to zero. Overexposure causes an initial increase then a decrease in bandwith and a blue shift plus a compression of contrast or dynamic range."

So, from 50% RH to 75% RH, and from 20C to 27C, sensitivity increases 15 times! Not 'just slightly', but drastically. And for blue light, figures are even better.

But my concern is currently about proper "annealing" or proper "aging" of the emulsion (in hope to get less milk, more image).
Tony DCG wrote:I'm happy you are trying a different gelatin. That's where my money is. I will again offer some of mine if you would like. I again say this so that you can minimize the amount of variables you have. If you have know good gelatin, you look at other parts of your process if the problem persist.
You are also right about different gelatin type. Perhaps all that idea about messing with aging and different way of drying and dealing with the emulsion is futile if gelatin I have is by default bad for the holographic purpose. Or too soft, or has too much additives (I bet too much additives, and too soft as well).

Maybe you are right about all of that. If gelatin is wrong, then no matter what I try it will give me the same bad results. But, I want to be sure that my procedure is correct.
Tony DCG wrote:As always, best of luck and thanks for posting!
Thank you for good ideas,

Best--
milan

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

Milkyness in dcg

Post by Tony DCG » Fri Mar 01, 2013 5:08 pm

[/
MilanKarakas wrote:But my concern is currently about proper "annealing" or proper "aging" of the emulsion (in hope to get less milk, more image).
MilanKarakas wrote:DCG Masters for Single Beam Photopolymer CopiesRichard D. Rallison
Last edited by Anonymous on Fri Mar 01, 2013 5:14 pm, edited 1 time in total.

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

Milkyness in dcg

Post by Tony DCG » Fri Mar 01, 2013 5:10 pm

Tony DCG wrote:[/
MilanKarakas wrote:But my concern is currently about proper "annealing" or proper "aging" of the emulsion (in hope to get less milk, more image).
MilanKarakas wrote:DCG Masters for Single Beam Photopolymer CopiesRichard D. Rallison
R Rollison was a great DCG holographer so who am I to foo foo what he is saying. If your goal is narrow band holograms then indeed this works fine. I simply store mine in a cooler (depending on weather I might regulate it with a cooling system) and some dissicant to keep it dry. A week is fine although even after a month it seems to work fine. If your goal is to get less milkiness then just age it. IMO humidity and heat ages film but not in a good way it will desensitize it so be careful. I guess heating is OK but again IMO results will vary, by how much is hard to say. Richard found a method that works for him as I did and as you will.

This is where I started. State of the art simple. http://www.holograms3d.com/MakingHologr ... graphy.htm


[/quote="MilanKarakas"]Maybe you are right about all of that. If gelatin is wrong, then no matter what I try it will give me the same bad results. But, I want to be sure that my procedure is correct.

Yes I hear you :) Been there ;) . You sometimes have to kiss a lot of ugly girls before you get a pretty one:)

Keep up the fine work!!

holomaker
Posts: 673
Joined: Wed Jan 07, 2015 8:01 am

Milkyness in dcg

Post by holomaker » Thu Mar 14, 2013 8:15 am

Tony DCG wrote: You sometimes have to kiss a lot of ugly girls before you get a pretty one:)
HOLY S%#& ...... How did i miss this one. Its the best quote of the thread! RFLOL ! Thanks Tony (and the rest of you guys too!)

ahgu
Posts: 23
Joined: Tue Dec 08, 2015 11:30 am

Re: Milkyness in dcg

Post by ahgu » Fri Apr 27, 2018 11:43 am

Joe,

Can you give me the ratio in weight? Not sure if the % is in mole?




I'm using a post-exposure bath which works well, as follows:

Part 1: Sodium Metabisulfite (1% solution in water)
Part 2: Aluminum Sulfate (0.2% solution in water)

User avatar
admin_jsfisher
Site Admin
Posts: 94
Joined: Sun Jan 04, 2015 12:35 am

Re: Milkyness in dcg

Post by admin_jsfisher » Fri Apr 27, 2018 12:19 pm

ahgu,
You may have missed the dates on the other posts in this thread. They are from five or so years past.

/JSFisher

Post Reply