--- In
Homebrew_PCBs@yahoogroups.com, "lmri2071" <lmri2071@...> wrote:
>
>
> I had this idea about seven years ago. But at that time the Laser Diodes
> of 405nm were impossible to obtain (USD$4000).
...
I have been experimenting with ammonium di-(or bi- same thing) chromate and gelatin emulsions off and on for about a year and a half. Though I don't know the chemistry very well, it seems that potassium, sodium or ammonium dichromate all have the ability to crosslink (harden) any number of organic materials when exposed to light.
I use fish-gelatin (aka fish-glue) which was once used to make the masks in TV picture tubes and other chemical milling processes. It is a kind of gelatin made from fish from Northern oceans. Due to its amino acid composition remains liquid at room temperature. I have no special reason to think that it is necessary. It wasn't terribly expensive, but then neither is Knorr's at the grocer's.
The Dichromates are indeed hazardous, as is any form of hexavalent chromium. Much of the negative experience with it comes from the plating industry, I believe.
That said, I worked with it a lot during my squandered youth, experimenting with gum-bichromate printing of photos. I gave that up one day when I inhaled enough of the powder to give me a headache and make me nauseous. I'm much more careful now.
The induction period for most chemical carcinogens is hopefully less than twenty years. Now forty years on I believe that something else will probably get me first.
-- Dave