Kodak rapid fix working life.

Steven · Post by **Steven** » Tue May 13, 2014 1:11 pm

For those that use Kodak rapid fix in their DCG processing, at what point do you determine that your working solution needs replacing?

I'm trying to figure out how many 4inch x 6inch DCG plates a half litre of working solution (diluted 1-7 per paper) will process.

Many thanks,
Steven.

dannybee · Post by **dannybee** » Tue May 13, 2014 10:46 pm

you will kind know if its too weak, but it will last a long time, when you put your plates into the fixer you will see the dichromate going into the fixer (its a blue green color) when that stops happening to time to use a new batch, i reuse my fixer bath till its too weak some change it every time you do a new setup

Steven · Post by **Steven** » Wed May 14, 2014 7:43 am

dannybee wrote:you will kind know if its too weak, but it will last a long time, when you put your plates into the fixer you will see the dichromate going into the fixer (its a blue green color) when that stops happening to time to use a new batch, i reuse my fixer bath till its too weak some change it every time you do a new setup

Thanks for that Danny.

holomaker · Post by **holomaker** » Thu May 15, 2014 6:26 am

Yes I to gauge the use by a test exposure and also the amount of blue the fixer as well, you will only get a feel for this by experience. .....

Steven · Post by **Steven** » Thu May 15, 2014 1:17 pm

holomaker wrote:Yes I to gauge the use by a test exposure and also the amount of blue the fixer as well, you will only get a feel for this by experience. .....

Thanks for that Dave.
Do you agitate the plate while it's in the fixing bath?
I found that if I don't get the agitation right, it can result in a variation of hardness across the plate.

Steven.

Joe Farina · Post by **Joe Farina** » Fri May 16, 2014 8:12 am

Steven wrote:I found that if I don't get the agitation right, it can result in a variation...

Yes, the question of agitation is a very good one. It's my feeling that agitation is good for just about everything in DCG. The problem is how to agitate.

I'm working on a homemade tray rocker. I have a portable griddle with thermostat, like this one:

http://www.amazon.com/Presto-07039-Elec ... le+griddle

I'm experimenting with keeping my (covered) processing trays (i.e., Lock & Lock) on top of a thick aluminum slab (to even out the heating) and have this on top of the griddle. I've found that the liquid temperatures are quite stable, and the temps can be varied individually by keeping some kind thermally-insulating material under each tray. The thickness of this material can be varied to change the temperature of the liquids in each tray. But the liquids need some kind of circulation, and I'm working on this now. My idea was to rock the griddle. I'm still trying to figure out how to do this, maybe by taking a couple of hot water bottles (a miniature "water bed") placing a board on top of them, then the griddle on top of that. Then find a mechanical way to rock the board, maybe by using a gear reduction motor (slow speed, maybe ~14rpm) with some kind of gear system to get the necessary up/down rocking.

jsfisher · Post by **jsfisher** » Fri May 16, 2014 1:31 pm

Side-to-side may be just as easy to do as a rocking motion. The advantage of side-to-side is that all the trays get sloshed around equally while with rocking it depends on distance from the pivot point.

Steven · Post by **Steven** » Fri May 16, 2014 3:24 pm

Joe Farina wrote:
Steven wrote:I found that if I don't get the agitation right, it can result in a variation...
Yes, the question of agitation is a very good one. It's my feeling that agitation is good for just about everything in DCG. The problem is how to agitate.
<snipped>

Hi Joe,
My method of agitation in the IPA baths is to hold the two side edges of my plate between thumb and forefinger and to plunge the plate down into the IPA flat (horizontal).
While holding the plate tightly, I move (force) the plate up and down rapidly through the liquid.
Like yourself, I use lock & lock containers for all my IPA baths, the depth of the IPA in my containers is about 1.5 - 2 inches.
I only agitate for about thirty seconds in the IPA baths, then clip the lids back on as I don't have an extractor system for the vapour.
I have found that the first IPA bath after the swelling water bath is the most critical of the IPA baths re agitation.

My fixing bath is a traditional photo development tray, which I agitate by rocking from end to end.
Maybe using a larger development tray and larger quantity of fixer would give me more consistent results.
What do the professional holographers out there do?

I do have an old large Salton hot tray, but I don't use it for heating IPA. I use it for heating my glass moulds when I'm coating, which I'm doing this evening

Well I have a couple of plates that need processing, so I'm going to mix up some fresh rapid fixer and try my up and down agitation method in a clip & lock container.
I will let you know how I get on.

Steven.

Joe Farina · Post by **Joe Farina** » Sat May 17, 2014 5:37 am

Thanks, Steven, for sharing some of your methods.

Due to the thickness of my DCG films, my processing times tend to be rather long, so I'm looking for ways to standardize/automate them. Rocker platforms often appear on eBay, I was wondering if anyone here has experience with them, such as:

http://www.youtube.com/watch?v=Hw2EsubyKTw

Steven · Post by **Steven** » Sat May 17, 2014 7:47 pm

Joe Farina wrote:Thanks, Steven, for sharing some of your methods.

Due to the thickness of my DCG films, my processing times tend to be rather long, so I'm looking for ways to standardize/automate them. Rocker platforms often appear on eBay, I was wondering if anyone here has experience with them, such as:

http://www.youtube.com/watch?v=Hw2EsubyKTw

You are welcome.
They are the methods I use, they may not be the right ones though

I'm not sure if using a mechanical rocker/agitator would introduce a form of regular patterning in your processed work.
There is an advantage to having some randomness in our agitation.

I'm processing for narrow band, so my bath times tend to be long like yours.
I'm using mould coating with 56µm shims and a 30g/200ml mix. I guess my coatings are about 9-11µm when dry.
I would like to try a coating of around 15-20µm, but I don't want to make it by adding more gelatin to the mix as it would take far too long to filter

Well I tried the up/down agitation with a couple of plates in a new fixer bath last night.
I think the results are better than just rocking in a tray, but it does require a larger volume of fixer.

Now off to prep and sensitize a couple of plates.

Steven.