Refractive index of gelatin

[alanrockwood]

What is the approximate refractive index of gelatin in a film?

Thanks.

 

[Europan]

http://www.geocities.ws/physicsexperiments/toate/4.pdf

 

[Nodda Duma]

It should be around 1.35-1.4 but I'll dig into my references.

 

[RobC]

why would you want to know this?

 

[Nodda Duma]

I dug around for a bit and found some information from the use of gelatin film for holography (where precise index of refraction values for gelatin really does matter).

From "Silver-Halide Recording Materials: For Holography and their Processing" by Hans Bjelkhagen, pg 242 (published 2013):

Dry, pure gelatin has a refractive index of about 1.54. A holographic raw emulsion has a higher refractive index on average since it also contains silver bromide. Bryngdahl [6.81] reported that the Kodak 649-F emulsion undergoes a change from 1.61 to 1.56, and the Agfa 8E75 emulsion from 1.63 to 1.53 during (amplitude) processing, both measured at 633nm. Syms and Solymar [6.82] found that the Agfa 8E56 emulsion had a refraction index of 1.62 before processing and 1.59 after bleaching, a drop of 2%. These values are the real values of the index...

So a bit higher than I thought it would be, but it makes sense intuitively. For lower wavelengths (ie towards the blue end), the index will be higher than the values measured at 633nm. So the other bit of information you'll need is the Abbe number..ie dispersion, which will provide you information on how the index changes as a function of wavelength.

-Jason

 

[alanrockwood]

why would you want to know this?

I want to compare the refractive index of film to the index of mounting fluid. The closer the two match the lower will be the amount of reflection at the interface. Also, a similar consideration applies to the difference between mounting fluid and glass. (Actually it's a little more complicated than this, since there would two interfaces in close proximity, but I won't go into that.)

 

[Mustafa Umut Sarac]

Alan , if mounting fluid irritates you , you can buy a anti newton spray or hair spray and spray to film and than directly mount it . I dont know whether it was for drum scanner or enlarger . You can mount also with acetate film on top of film. Its bit difficult but highest quality comes from it. Glass - fluid - film - fluid - acetate - very thin - You have to have a film mounting jig with pressure roller to remove the fluid and stay with thin layers. You can do that with taping the acetate and strech and press with other hand on to matrix to remove the unnecassary fluid and clean clean clean and look with a loop to finding errors. Strech, tape and clean.