>But any way you cut it, ammonium dichromate is a nasty substance that just
>loves to crosslink collagen; of which there is plenty in the human body.
>So be careful with this stuff.
Yes, quite. If you've seen the "Erin Brockovitch" (sp?) movie, the
substance that was getting into the groundwater (and ruining people) was
hexavalent chromium, which is the ammonium, potassium, sodium, etc.,
dichromates.
I believe that the information on chromated gelatin over at the
holography site includes something regarding mixing waste dichromate
solutions and wash water containing dichromates with used photographic
developer, which changes it to an insoluble form. This drastically
reduces it's impact.
I used to be involved in the corporate use of this process on a
relatively small scale, and they eventually had to stop and find a
replacement. An industrial silkscreen-making goop (diazo?) ended up being
the thing, it dropped right into the process (being sprayed on, resisting
acetone, coming off with bleach, etc). The toughest part was figuring out
how to measure it out for amounts much smaller than the one-gallon kit.
In the above process, I was aware that a competing company would add
Elmer's white glue to the mix when they had adhesion problems with the
plain gelatin/dichromate mixture. I'm not sure if they realized that the
glue was also crosslinking.
The green pigment may not be the best choice for sensitizing (the
base mixture requires UV). Look on the holography site for information on
red-sensitive DCG - although then you'll have to use a dark green
safelight, which gives rise to the phrase "working in the green
darkness". It's probably easier to come up with enough UV, I expose UV
sensitive resist with a cheap 500 watt halogen with the UV shield glass
removed (~4 minutes at 18 inches through an old glass-topped photo
contact printer).