Blackening the emulsion for reflexion holograms

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thycore
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Blackening the emulsion for reflexion holograms

Post by thycore » Mon Dec 30, 2019 10:04 am

Hi there,

An old (and closed) topic on the forum : https://holowiki.org/forum/viewtopic.ph ... cb6#p57579

Refers as a technique from Jeff Blyth to use Sodium Borohydride (Tétrahydruroborate de sodium in french) to blackens the rear part of the emulsion after it's been developed, bleached and dryied. I can't wait to test this technique, I ordered some NaBH4 on eBay.

The formula provided for this blackening bath is as follows :

650ml methanol
350ml dionized water
0.5g sodium borohydride

Any idea if Isopropyl alcool (IPA) can be used instead of Methanol ? (I have like tons of this at home..)

Steven
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Re: Blackening the emulsion for reflexion holograms

Post by Steven » Wed Jan 01, 2020 11:33 pm

I have tried the blacking agent you have described over thirty years ago, but I never tried it with IPA.
It did work and as far as I can remember, the film fizzes when placed in the solution.

Steven.
Success through failure - the amateur DCG holographer's path to enlightenment.

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thycore
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Re: Blackening the emulsion for reflexion holograms

Post by thycore » Thu Jan 02, 2020 2:05 pm

Okay, not sure if fizzing is a good or bad thing but I take this is not a desirable effect xD

Steven
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Re: Blackening the emulsion for reflexion holograms

Post by Steven » Fri Jan 03, 2020 9:43 pm

I think that the fizzing was just part of the chemical process taking place.
The blackening agent did work quite well.
Success through failure - the amateur DCG holographer's path to enlightenment.

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thycore
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Re: Blackening the emulsion for reflexion holograms

Post by thycore » Sat Jan 04, 2020 3:57 am

We should add a section « Blackening » in the wiki part of the website to write this down :-) I’ve been struggling with laminoir or black paint for like 2 years with pathetically discussable results xD

BobH
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Re: Blackening the emulsion for reflexion holograms

Post by BobH » Sat Jan 04, 2020 9:53 am

What difficulties have you had with paint? A solution may be to seal the hologram with epoxy or RTV (like Ron & Bernadette Olson use), and a piece of glass. Then paint the back. Use a piece of smoked or black glass and you may not need to paint.

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thycore
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Re: Blackening the emulsion for reflexion holograms

Post by thycore » Sun Jan 05, 2020 6:23 pm

I’m using holographic film from an antique Holofilm250PAR lot. These films does not like to keep the paint on it, probably due to flexibility, the paint tends to scale out ( damaging the hologram by the same way).

I simply like to idea that a chemical process exists to make it just perfect easily :-)

Sergio
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Re: Blackening the emulsion for reflexion holograms

Post by Sergio » Mon Jan 06, 2020 4:31 pm

The Liquitex Professional Spray Paint is water based and can perform perfectly:

https://www.amazon.com/Liquitex-Profess ... lp_pl_dp_3

Also by Montana colors:

https://www.sprayplanet.com/products/mt ... rbon-black

This one I did not test but for Liquitex it is OK.

soda
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Re: Blackening the emulsion for reflexion holograms

Post by soda » Tue Jan 07, 2020 12:05 pm

The best way how to handle the holofilm250 I found use few drops of LOCA uv glue (cheap on ebay for cell phone repair) to sandwich it to glass and press the sandwich firmly, then irradiate it by the UV lamp (or direct sun). Then the hologram can be used as master from the other side, or simply paint the back glass to black. An acrylate based black spray also can be applied directly to the emulsion side.

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thycore
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Re: Blackening the emulsion for reflexion holograms

Post by thycore » Tue Jan 07, 2020 3:33 pm

What exactly does UV on this film ? Do you use it on freshly developed / bleached film ? Is it acting like a « fixer » ?

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