Adding alcohol to the gelatin?

[jsfisher]

In the early pages of Silver-Halide Recording Materials: For Holography and Their Processing, Hans I. Bjelkhagen describes the silver-halide emulsion manufacturing process. On page 35, I found this:

V) Coating. The final step consists of coating the emulsion on a suitable substrate. The emulsion is melted, after which certain solutions, known as doctors, are often added to facilitate coating and to modify the physical and sensitometric properties of the film. Alcohol, for example, may be added to reduce froth formed during coating; glycerin, to make the dry film more pliable; surface active agents, such as saponin, to make the film more easily wetted by the processing solutions, etc. The doctored emulsion in liquid form is then piped to a coating machine where it is applied to the substrate material.

I've underlined the part I thought interesting. If alcohol reduces froth formation in the warmed, liquid gelatin, might it also reduce bubble formation? Sounds like it would be worth a little experimentation.

[holomaker]

If alcohol reduces froth formation in the warmed, liquid gelatin, might it also reduce bubble formation? Sounds like it would be worth a little experimentation.

Better to practice not having any bubbles to begin with, John what method do you coat with?

[dannybee]

In the early pages of Silver-Halide Recording Materials: For Holography and Their Processing, Hans I. Bjelkhagen describes the silver-halide emulsion manufacturing process. On page 35, I found this:

V) Coating. The final step consists of coating the emulsion on a suitable substrate. The emulsion is melted, after which certain solutions, known as doctors, are often added to facilitate coating and to modify the physical and sensitometric properties of the film. Alcohol, for example, may be added to reduce froth formed during coating; glycerin, to make the dry film more pliable; surface active agents, such as saponin, to make the film more easily wetted by the processing solutions, etc. The doctored emulsion in liquid form is then piped to a coating machine where it is applied to the substrate material.

I've underlined the part I thought interesting. If alcohol reduces froth formation in the warmed, liquid gelatin, might it also reduce bubble formation? Sounds like it would be worth a little experimentation.

I Have use ISO (alcohol) in my mix it does help .. a small amount

[holomaker]

John what method do you coat with?

[jsfisher]

John what method do you coat with?

Veil. Sometimes with a 78 rpm spin afterwards. To date, I've played only with very small plates--2.5x2.5" plates reclaimed from less successful silver-halide attempts and 3x2" microscope slides.

[holomaker]

When you transfer you emultion to the plate use a pipett and you wont have bubbles .

John when you spin coat such a small plate the pulling action dosent work so well as the center of the plate gets very little force, if you make larger plates (and then cut them smaller) i think you will have an easier time coating..............

[dannybee]

alcohol is a wetting agent

[Johnfp]

Danny, does that mean you had trouble with the emulsion sticking to the glass when alcohol was added?

[Johnfp]

jsfisher,
do you filter the emulsion through a coffee filter or two after cooking? That usually take care of all the bubbles and any fine particles that would cause a pit in your final hologram.

[dannybee]

Danny, does that mean you had trouble with the emulsion sticking to the glass when alcohol was added?

not that I recall, it does the same as adding photo flow (a wetting agent) but a bit better.