This is a much better video of how to make ultrasound gel than the one I originally published. Thanks to Christopher Snyder for putting it together, playing the piano and getting my sister to play the guitar for the sound track. It makes the process of boiling water and adding guar gum feel noble and inspiring.
The guar gum recipe here works better than several other thickeners I tried. See this article for details:
http://whyisamericanhealthcaresoexpensive.blogspot.com/2013/02/how-to-make-your-own-ultrasound-gel.html