I found this interesting black and tan video demonstration at the doingsciencetostuff blog. Really shows the principle of density-based layering at work. Check it out at http://blog.doingsciencetostuff.com/2013/09/21/epic-black-and-tan/
We would love to post your pictures in this blog. Send them to firstname.lastname@example.org
Click here to request a PDF copy of our instructions booklet.