The Two Sides of Vitamin C

Vitamin C or ascorbic acid, as it is known, is essential for our health. To look at it's just a white powder - nothing remarkable but observe crystals under crossed polarized light and it is transformed into a blaze of colours.

One winter evening I decided to try it for myself. I dissolved vitamin C powder in warm water till I had a fairly concentrated solution. I added a few drops to a microscope slide and lowered a cover slip over the liquid to give a thin even layer. As it cooled crystals soon began to form and I watched the process under low power, fascinating in itself.

I had bought some polarizing filters from ebay for just a few pounds and tried them out. I placed one above the microscope light source over the condenser and the second I rotated above the sample until all light was blocked out. Now I moved the crystals in to view and carefully focused on them. I had seen pictures of the crystals under cross polarized light before but I was still unprepared for what I saw. Colourless crystals had been transformed into blazing multi coloured patterns everywhere I looked. Peacock feathers, firework displays, pyschedelic patterns - so many variations that I took hundreds of photos. Each time I tried it I saw different variations , some on a common theme but all subtely different. My favourites are posted here. Maginifications vary from 40x to 200x.

How does it work? A polarizing filter lets light through vibrating in one direction only. The second filter is oriented so it only lets light through which is vibrating at 90 degrees to the light from the first filter.The scientific term for this setup is cross-polarization So no light gets through. If you place a substance between the two filters which can affect the path of the polarized light rays from the first filter some will get through split down into various wavelengths or colours. Such a substance is Vitamin C and it is said to have birefrigent properties. I am experimenting with other substances and will post my results in the future.

The Science of Soap Bubbles

Have you ever noticed the swirling colours in a soap bubble? I wondered if it was possible to photograph them under the microscope using washing up liquid. I put a few drops of washing up liquid  and water on a watch glass and  added a drop or two of glycerine to make the bubbles last longer. I used a pipette to create various sized bubbles by blowing air through the mixture. I was able to create suitable sized bubbles about half inch across.

Using 60x magnification with the stereomicroscope I could see patterns starting to form after several seconds but the lighting was causing unwanted patterns in the picture. I needed a diffuser so I used a plastic diffuser plate from an old slide viewer and focused on the bright reflection of the light on the bubble surface. The resulting photos are shown here. The patterns are beautiful starting with pinks and greens and progressing to blues and yellows before the bubble pops.

These two images show a predominance of pinks and greens because the bubble film is relatively thick.

Here yellows and pale blues are starting to form as the bubble thickness decreases with time.

Now for the science.  A soap bubble consists of 3 layers. A top layer of soap molecules, a central layer of water molecules and an inner layer of soap molecules. When light strikes the outer surface of the bubble about 4% of the light is reflected back. More light is reflected back from the inner surface and because the thickness of the film is in the region of light wavelengths interference between the two can occur. The type of interference depends on the thickness of the bubble film and the particular wavelength of the light.  If two reflected waves line up (ie in phase) the interference is constructive. If they don't then the interference is destructive. So the beautiful colours you see in a soap bubble are intereference patterns.

Therefore, everywhere you see yellow, the film is just the right thickness to destructively remove the blue light waves. Where you see cyan, the red light has been destructively removed. And where you see magenta, the green light has been destructively removed. The progression from pinks and greens to blues and yellows occurs as the bubble thickness decreases with time.

This image was taken shortly before the bubble burst. Note the blues and yellows.

Just before the bubble bursts deep blues and yellows appear as the film gets thin.

A bubble planet.

Dove's Foot Cranesbill - Geranium molle

Dove's Foot Cranesbill - Meiji EMT  30x 

I've often seen these tiny pink flowers in the local parkland and wondered what they were. Closer examination revealed colourful purple stamens loaded with pollen. I discovered that they were a type of wild geranium which always make good photographic subjects. The name Cranesbill derives from the Fruit's resemblance to the bill of a Crane.

Dove's Foot Cranesbill - Meiji EMT  60x 

 Pink stamen and anthers bearing spherical shaped pollen.

Dove's Foot Cranesbill  - Apex Researcher Microscope,  Canon 550d , 100x 54 images Stacked with PS5

Dove's Foot Cranesbill  - Apex Researcher Microscope,  Canon 550d , 200x 51 images Stacked with PS5

Bubble Art

Apex Researcher Microscope 40x, Brightfield, Rheinberg Filter.

Bubbles are fascinating. These photos are all of air bubbles in water to which a drop of washing up liquid has been added. My method is simple: I just put a small amount of tap water on a watch glass. Add one drop of washing up liquid and use a pipette to blow air back and forth through the mixture until a good load of bubbles have formed of all different sizes. I put the watch glass on a microscope slide and place that on the microscope stage. It is then easy to move the watch glass using the stage movement controls. I use the microscope's lamp as normal as the light source and place Rheinberg filters (which are basically circular pieces of transparent coloured plastic) of various colour combinations for the coloring effects, above it.

Meiji EMT microscope 60x, Brightfield illumination with Rheinberg Filter.

 You can learn a lot of physics from studying bubbles. In fact there are scientists at Cambridge  and other Universities who study them for a living! The science can then be applied to many other problems. Here is a video explaining why bubbles are the shape they are. and another hour long documentary called "Pop!" about you guessed it - Bubbles!!! Basically bubbles are spherical because that is the lowest energy configuration and gives the largest enclosed volume for the smallest surface area but interesting things happen when bubbles join... see the above videos.