Home-made Shock diamond Is there any way of creating a "home-made" effect of shock diamond phenomenon that I could take a picture of? If so, How could I make one?
 A: Sorry Dan, the answer is "NO"...
Shock diamonds are produced when there's a huge difference between the exit pressure and the ambient pressure. A series of shocks and expansion fans form to match the radial distribution of the flow's exit pressure to the ambient environment. Much more simply, those phenomena are very necessary (and the only ones available) to introduce a discontinuous change in the flow properties.
In aeronautics, we say "Mach" ($v$ to $c$ ratio) only when something attains a good percent of the speed of sound in that medium (which here is air). That "supersonic" property should be noted because these are seen only during blasts of gas (at a nozzle, a vent or artillery) at supersonic speeds which are impossible to attain while sitting at home and watching TV. In order to do such things, you'll require a large space, loads of fuel and mainly "an afterburner"...
Note: I mentioned that you simply can't create those diamonds. But, you could do a lot of things in photography. Like, picturing some cool flame torches in oxy-acetylene (or an alkane) welding torch and do some tricks using whatever you've got good in image effects. Or, you could blend some to create diamonds like these people.
If you still wanna see a shock, you'd need something like the Schlieren apparatus. Balloon pops & bull whips also produce shocks. They can be photographed using the schlieren, and so if you have access to a supersonic testing laboratory (where these experiments are quite common), you may end up in something cool. In jet aircrafts, the visualization is provided by the flames and so, a schlieren is not required in that case.
Last year, we used the apparatus to visualize those shocks. Here's a grey-scale image of the exit. Shocks can't be seen (for they're of the size of a few molecules), but the dense cones indicate the region behind those shocks where there's a giant bunching up of the fluid molecules...

A: You definitely can! Shock diamonds form even through pressure differences as small as 60 psi. 
Don't believe me? Try it for yourself. Take a can of compressed gas (like computer duster) and spray it and carefully look at the gas coming out of the front... You will notice a subtle but never the less present shock diamond pattern. To make the pattern more clear try shining a bright POINT SOURCE light (like a laser beam that has been spread out with a lens) so that the shadow of the gas coming out is clearly visible. You will see the shock diamonds much more clearly if you look at the shadow of the gas! I've done tons of experiments with this and it's awesome! 
A: I don't have a picture but I do have this video I made which I think should help. https://www.youtube.com/watch?v=-eGTuNfc_kk
Ty
