This is a first for me, but it’s incredibly easy to do with the right tools. You’re looking at crystallized citric acid! No trickery here, and the recipe is extremely simple.
First, make a mixture of distilled water and Isopropyl Alcohol, 1:1 ratio should be fine, and you don’t need very much. I made about 100ml worth, and that was more than enough. Next, add in citric acid powder. This can be easily purchased for a few dollars on Amazon – it’s used as a food preservative. How much? I put in a heaping spoonful. The idea is that you want to saturate the liquid with the dissolved citric acid, so that it will crystalize as the water / alcohol mixture evaporates. It takes less than 10 minutes for all the powder to dissolve.
Next, use a syringe, pipette, or eyedropper to place some droplets of this liquid on a microscope slide. Don’t have slides handy? Take the glass out of a picture frame! Works just as well. You can try placing circular drops, and even spread them out with whatever you used to place the droplet with some smudging. The thinner, the better.
Now, wait a few hours.
Next, we need two polarizing filters – one on your light source, and one on your camera. Here’s a behind-the-scenes image that showcases the somewhat haphazard arrangement I’m using: donkom.ca/bts/citricacidbts.jpg . The effect we’re after here only shows itself when we polarize our light source, then polarize the light on the other side of the subject in the opposite direction. Normally, we’d see nothing – the crossed polarizers would block most of the light, which is exactly how variable neutral density filters work. However, what if something between the two filters mucks about with the direction of the polarized light?
We call the effect “birefringence”. Certain materials will have a different refractive index (light will bend to a greater or lesser degree when passing through) based on the direction of the polarized light. Biaxial materials will have three refractive indices that correspond to the principal angles of the crystal. I won’t go deeper here, as I feel I’m even losing myself in the explanation: simply put, polarized white light reveals crazy colours, and subtracting the original unaffected light, or simply adjusting the direction of polarized light on either side of the subject will give you different colours.
This was shot using the new Novoflex CASTEL-Micro automated focusing rail, which I prefer over the Cognisyst Stackshot in terms of absolute accuracy in movement and calibration. The image is stacked mostly because I’m not using a proper microscope and the slide isn’t perfectly parallel to the focal plane of the camera. I’m also shooting with a Novoflex tube lens and a Mitutoyo 10x objective. This type of imagery can be easily done with a Canon MP-E 65mm or Laowa 25mm super macro lens that gets up to 5x magnification, and crop to taste.
And yes, a full comprehensive write-up will be included in my upcoming book: skycrystals.ca/product/pre-order-macro-photography-the-un...