Holographyforum.org / holowiki.org

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..)

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.

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

I think that the fizzing was just part of the chemical process taking place.
The blackening agent did work quite well.

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

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.

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

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.

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.

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