It's going to be a gas unless you hit the right pressure. Here is a phase diagram for CO2: http://stevengoddard.files.wordpress.com/2010/09/co2_phase_diagram.gif and H2O so that you may compare and see what's at work: http://chemwiki.ucdavis.edu/@api/deki/files/2657/=Phase_Diagram_H2O.jpg To be supercritical CO2 must be at 304K under ~73atm of pressure. (73 times atmospheric pressure, that is alot) I have a hard time believing that a normal test tube can withstand such pressure. I am guessing the one used in the video was a specialized version, and is likely not THAT cheap. Also, the fact that the CO2 is boiling off tells me it's unlikely that 73atm could even build up in that tube--that amount of dry ice probably doesn't even have the capacity to send pressure that high, perhaps locally but no throughout the sample. The idea behind supercritical extractions is that things are selectively soluble at different pressures/temperatures in CO2 above the critical point. Without precise control over the temp/pressure almost all of the utility gained by using this as a solvent is lost. Butane begins to look a lot better economically for a number of reasons. This is essentially why more people aren't doing this already.