Holographyforum.org / holowiki.org

Hello everyone !

I’m having difficulties in achieving a uniform drying of my silver halides emulsions ( using kodak flo) i somehow still get some stains/color-shifted zones.

I was considering drying in alcool baths, like for DCG... Anyone tried already ?

Are you talking about reflection holograms or transmission holograms?

Drying in alcohol works well for Agfa plates. It doesn't seem to work so well for Slavich plates.

The issue may be that you're not setting up the plates to dry vertically. After the photo-flo, you have to prop the plates vertically, or at an angle, with a paper towel underneath to absorb the water as it flows off the plate. If you simply let the plate dry by evaporation, some parts of the plate will dry faster than other parts, causing discolouration. Also, if you agitate, you'll get bubbles, which will also cause discolouration.

For Slavich plates, I use a few drops of photoflo in about 250 mls of water (about 2% - 3%). dip the plate into the photoflo, shake (not agitate) the plate a couple of times, and place it at a small angle with a paper towel underneath. The paper towel is to absorb the solution, so it doesn't collect at the bottom of the plate and get re-absorbed.

Alcohol drying of Slavich plates is described by Sergey Vorobyov here:
http://www.holography.ru/les11eng.htm

Anyway, I have no direct experience with it, I do not use Slavich plates any more.

Thank you for sharing that link Petr. I would add the following comments. Long before the 1980 paper referenced by McGrew’s paper in the link, Andreas Graube at Hughes Research and Rich Rallison in Utah (and maybe others) detailed their usage of alcohol drying of gelatin based holograms. In 1976 & 77, I studied with Steve Benton, who was then at Polaroid before he later became head of the MIT Spatial Imaging group, and he taught us the 4 step alcohol drying process referred to in the link. He taught us to use a 100% alcohol spray on the plate though rather than using a brush. This would eliminate the “glass splinter” concern. In 1976 & 1977 we used the less expensive methanol until we realized how much safer ethanol is. This was for drying transmission holograms and, at the time was not recommended for reflection holograms. Another issue re glass splinters- it wasn’t until the early 1980s that Agfa began smoothing the edges of all their glass plates. Typically, Agfa produced plates in 1 meter square format and cut them down for smaller sizes which is what led to the glass splinters in the emulsion. If you come across a batch of old unexposed Agfa plates you can get a very rough estimate of their age by checking the edges. The Millimask line (exactly the same emulsion as 8E56HD) made for the electronics photomasking industry back then always had smooth edges as did the Kodak HRP UltraFlat line.

Here are a couple of samples of normal vs alcohol drying on some Agfa 8E56HD film in contact with coins, done the other week:
CWC2 developer, bleach in a rehalogenating bleach, see here:http://edweslystudio.com/Formulae/Bleac ... leach.html. The one on the left was washed in water after the bleach, soaked in Ilfotol, then air dried; the one on the right, washed after bleach, then 2' in 50% IPA, 70%, then 100%, all at room temperature, about 20C. Blown dry with a hair dryer. Interesting upshift in color.

Ilfotol is the Ilford equivalent of Kodak Photo-Flo, but I have been having to dilute it 1:100 or even 1:50 to eliminate drying marks. I can tell if the dilution is successful by looking at the film base and seeing if the water flows off smoothly. I don't use tap water, but the steam distilled kind that is found at the grocery store, which I would hope is mineral free.

Thank you folk so much for your links and explanations

I reduced concentration of the flo in my a rincing bath in which (and in all baths) I now agitate my plate emulsion facing down to prevent splinters or particles deposit and had vertical drying ( without hair blower ) and my problem seems solved

Be careful, agitating with the emulsion down is a good way to wear a hole in the emulsion.