Photochromism

I've seen cars get paint jobs that change colors. Is this what your mean?

hey, just curios, but in flourescein video, you extract the water from the ether, with saltwater. was there any reason you didnt here, or any favorbel with the magnesiumsulfate method, becuz the one this saltwater look easyer.

Martin Kalum

In alternative process photography (which I've dabbed a bit amateurishly in) the coating of paper with a photosensitive mix is usually done with a "pusher". Which is a straight-edge spatula with which you push around the paper a small puddle of the chemical. Gives much better results than a brush.

Silviu T

You could consider spraying it on, or use surface tension/gravity to create a thin coating of soluted DNBP, and then either roll the paper over it only ever contating one line perpendicular to the movement of hte roll, or just fold it onto the glasss/puddle by slightly bowing the paper out towards it so it slightly gradually makes contact with the glass that has the puddle ov solvent with dnbp on it. Also think about/look at how printers handle such tasks, just consider the printing to be ov something that leaves a uniform surface, not fine dots or such....

Super interesting!

Thor Correia

that was very interesting!

Adam Rak

Something interesting I found is that a *lot* of things are photochromic. For example, PCB solder mask (it's not sure if it's just solder mask or also related to PCB substrate Tg--in any case it's useful for quickly gauging how hot it is), and to my sheer surprise... TiO2! Try it yourself: put some TiO2 in a test tube and blast it with a heat gun. My sample, which I got from a chemicals supplier and which was reasonably pure (and if it wasn't and it's some impurity, I think I still have it and might be able to send it to a lab), got very visibly yellow at around 200 °C.

Catherine

Man I have had a terrible day but watching this video was a great end to it

Slip0824

I was going to suggest the same, use a polymer binder. Maybe gelatin like Brian suggested, polyvinyl alcohol, or polyvinyl acetate (wood glue)

Gabriel J.

also as for your heat gun/water reset, you know what the melting point is? melting the crystals im sure is whats happening, and they are crystalizing with the water.

Adric Menning

its interesting that you got the reverse reaction in the epoxy, as i recall the epoxy often has uv blockers in it, to limit damage/yellowing, i found it greatly changed some of my glow in the dark powders, there was some obvious florescence under long wave light before it got to the powder, and not charging the powder as much, oddly it was a very uranium glass sort of glow.

Adric Menning

Very nice, especially the discovery of the reverse photochromism in epoxy. That was unexpected. As for ideas on coating paper to make temporary pictures. One idea would be to use the epoxy mixture, and use it as a negative paper (no wait I got confused: it would actually make positives out of a positive print: it starts dark, the regions shaded would stay dark and the regions exposed to UV would become discolored). With epoxy you may want to use a heavier paper or even cardboard (and even metal sheet, such as an aluminum plate). Another idea would be to mix an actual emulsion, either based on gelatin, PVA or polyacrylamide. You could mix an acrylamide gel, such as it's used for SDS-PAGE (no need for SDS though)and seal it between 2 glass plates to prevent evaporation of water. So much exploration of the subject is possible. And indeed, the reverse action of heat/water may have to do with changes between one crystal structure and another. I can't find any info about the different crystal structures of DNBP though. I appreciate your interest in photography and photochemistry - did you take that Pripyat photo yourself? That means you've been there. Little factoid, in April 1986 I was living within 300 miles of Pripyat. :)

Silviu T

Cool video! I'll be honest... I have nothing of value to add to the chemistry, but I'm doing my best to learn. Thanks for the engaging, entertaining content!

Adam Longmire

Try mixing the DNBP with a simple polymer like gelatin then coat some gloss cardstock or poster board with it. I remember doing that in Highschool with a silver salt to make a crude photopaper. Not sure if the DNBP would react with the gelatin but it might be worth a shot. Water color paper is porous so not ideal if you want everything exposed to light.

Brian Reddeman

I loved it!! When the color came back in the paper when you added water, my gut feeling says chrystalline water. That the heat gun waporated the chrystalline water. Still I'm not sure though. But still good work, and I think you do a important job by educating! :)

Alf-Marius Dahl Bysveen