Refridgerating DCG

This is a forum to share experiences and ideas about holography.
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JohnFP

Refridgerating DCG

Post by JohnFP »

I made some plates Saturday, let them cure for about 4 hours or so, then put them in the fridge. Sunday I made some holograms (they all turn out quite well for being out of the lab for what, almost 2 years) and I seem to think that they acted like young plates, like 4 hours old..

Has anyone else noticed that the refridgerating stops or greatly slows the aging process of DCG?

So if basically if I want to use a mature plate, I would have to manually mature it after I take it out of the fridge. I don't want to pre fridge mature the plates as then I would imagine it would cut down on length of time they would stay fresh in the frige.

Any thoughts?
Joe Farina

Refridgerating DCG

Post by Joe Farina »

Glad you're back in the fray, John. Yes, that's it exactly, refrigeration greatly slows the ageing process of DCG.
JohnFP

Refridgerating DCG

Post by JohnFP »

Here is one for you all.

Let's say I make plates and let them cure for 4 hours then put them in the fridge (mine is set to about 38F).

What is the relationship on aging to time in fridge?

In other words, plates put in fridge are 4 hours old. Do they cure/age 1 hour for every day day in the frigde or 1 hour for every week in the fridge, etc?

Anyone do any baselining with this?

I can usually tell how mature my plate are simply by processing them. So I will try to keep an eye out for this. Although surely without specifically studying this it will not be very scientifically accurate but I may be able to get an approximation. I'd love some input.

John
Joe Farina

Refridgerating DCG

Post by Joe Farina »

Sounds like a good thing to investigate.

In the booklet by Richard Rallison that I received as part of a tutorial on DCG, he states:

"DCG stores well at low humidity in a refrigerator or freezer but containers must prevent contamination, condensation, freezer burn and frost which can all destroy surface quality. Film 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 a few hours, thick films typically last a week or more. The addition of a small quantity of TMG to the mixture will greatly increase storage time at room temperature by increasing the pH."

There are a lot of things in this statement which would benefit from some controlled testing. Note for example the huge difference in storage times allowed at room temperature for thin versus thick coatings. In Rallison's writings, I get the impression that a thin coating might be somewhere around 5 microns, a "typical" or average thickness might be about 10 microns, and a thick coating would be about 20 microns or more. The addition of TMG is also an interesting alternative to refrigeration, but refrigeration works so well, that any extra substance introduced into the layer which would cause further shrinkage upon processing seems to be of dubious value. Also, TMG is hard to find.
Martin

Refridgerating DCG

Post by Martin »

Joe Farina wrote:Sounds like a good thing to investigate.

In the booklet by Richard Rallison that I received as part of a tutorial on DCG, he states:

"DCG stores well at low humidity in a refrigerator or freezer but containers must prevent contamination, condensation, freezer burn and frost which can all destroy surface quality. Film 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 a few hours, thick films typically last a week or more. The addition of a small quantity of TMG to the mixture will greatly increase storage time at room temperature by increasing the pH."

I've always been wondering about the quantity of TMG involved here. Since TMG is highly alkaline the good keeping properties of that mixture may simply stem from the dichromate being changed to chromate. If that was the case one might consider coating "DCG" plates with chromate rather than dichromate. Such plates might be stocked for an extended period of time. Maybe - not sure if that is doable - prior to exposing them holographically, it would be possible to put the plates in an acid environment (to turn the chromate into dichromate, in order to get better speed).
JohnFP

Refridgerating DCG

Post by JohnFP »

I will say, I think I like thick coatings better anyway. I think you can play/tune/change them more. I see this on the outside of my plates when I veil coat then spin.

I think for my next batch I may veil and then set the plate on a perfectly level surface such that the coating comes out thicker and skip the spin altogether.
Dutchelm05

Refridgerating DCG

Post by Dutchelm05 »

JohnFP wrote:Let's say I make plates and let them cure for 4 hours then put them in the fridge (mine is set to about 38F).

What is the relationship on aging to time in fridge?

In other words, plates put in fridge are 4 hours old. Do they cure/age 1 hour for every day day in the frigde or 1 hour for every week in the fridge, etc?

Anyone do any baselining with this?

I can usually tell how mature my plate are simply by processing them. So I will try to keep an eye out for this. Although surely without specifically studying this it will not be very scientifically accurate but I may be able to get an approximation. I'd love some input
I suppose the best way to do this is coat a plate and cut it in 4 pieces and then shoot one after 4 hours, that's your reference. Then place one in the frig and one in room temp and humidity and one say in a dessicant bag. Wait a week and try them.

The problem of coarse is determining how hard they are. All will require different fix time so it may require many plates to home in on it. There would be several variables that might change the outcome.

I think it would be hard to qauntify this. DCG is a moving target and while aging in one factor there are may others that also effect outcome. Temp and humidity before and during exposure as will as processing will effect the outcome. I once heard that DCG can even cycle meaning day 2 works good, day 3 not as good, and day 4 is good again. The black art of it makes it hard to isolate one varible. But we can try :angel: :?

I can say that placing plates in the frig preserves them very well. I use plates that are 2 weeks old and they as good as the day they were made.

So good to have you back John.
If you need verification on any test, let me know.

Tony
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