2
$\begingroup$

I'm producing thin sheets of liquid (50 to 100 microns) from a nozzle and trying to photograph them. I think it would help if I could color the water. However, typically as water becomes more of a thin film it tends to lose color. I'm wondering if anyone has any thoughts on this. I think white would be a particularly good color. Food coloring containing titanium dioxide might work. I know that just using milk will work, but it's a mess to deal with because I am dealing with sprays traveling at a minimum 5 meters per second.

$\endgroup$

2 Answers 2

1
$\begingroup$

Use fluorescein or other fluorescent dye, along with an effective UV filter (AKA haze or skylight filter) on the lens and an ultraviolet source, such as a xenon strobe (speed light) or UV flashlight. A UV-transmission filter on the strobe can increase contrast, and can be made cheaply, but might not be needed. Because fluorescence makes the fluid become a source of light, it is quite obvious against a dark background. You can even use most laundry detergents, which contain blue-fluorescing dyes -- though foaming might be a nuisance.

See this image of fluorescent soap bubbles or this one. Soap bubble film may be just a few hundred nm thick, yet show clearly with fluorescence. Also watch a demo of strobe illumination of water droplets using sodium fluorescein for contrast. In the video, notice, in particular, that the stream tends to break into pairs of droplets, one perhaps a millimeter in diameter, and the sibling, just a few microns across, but all clearly visible!

Choose a near-UV light source and fluorescent dye for safety, since shorter wavelengths are more damaging to eyes and skin. A search for UV flashlight returned items from US$10 and up, some of which might be suitable. Most were in the 395 to 365 nm spectrum, relatively innocuous.

$\endgroup$
6
  • $\begingroup$ I should have mentioned that I am taking pictures in the dark using a microsecond flash so that I can freeze the water. I don't know if a flash would work in conjunction with a black light. I'll have to do some internet research to see if anyone has tried that. $\endgroup$
    – Bob D.
    Commented May 6, 2020 at 19:22
  • $\begingroup$ Xenon strobes (speed lights) provide ample UV... no extra black light needed, then. $\endgroup$ Commented May 6, 2020 at 19:26
  • $\begingroup$ Oh, well that would be great. Thirty years ago, I used coumaric acid and it produced a nice green fluorescence. But I don't remember whether it was ortho, para or meta. $\endgroup$
    – Bob D.
    Commented May 7, 2020 at 1:13
  • $\begingroup$ My apologies. I should have read your first response more carefully. You provided this information before as well as a lot of reference info. Thanks so much. If this works, it should be really cool! $\endgroup$
    – Bob D.
    Commented May 7, 2020 at 1:22
  • $\begingroup$ @BobD, you didn't make any error reading the original... after you pointed out the use of strobes, I edited the answer. Best wishes for the photos; perhaps post one as part of your question, if the answer was of help. $\endgroup$ Commented May 7, 2020 at 2:26
0
$\begingroup$

Methylene Blue produces a very intense colour at quite low concentrations. It's also very cheap from places like eBay.It is also relatively non toxic

$\endgroup$
2
  • $\begingroup$ "Methylene Blue produces a very intense colour at quite low concentrations. It's also very cheap from places like eBay.It is also relatively non toxic" Thanks. I'm also looking in to the "ouzo effect". $\endgroup$
    – Bob D.
    Commented May 6, 2020 at 17:44
  • $\begingroup$ @BobD. Maybe try oil in water emulsion of metal cutting fluid? $\endgroup$ Commented May 6, 2020 at 18:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.