To actually "Cast" a blank ? I would say no . It would be to thick to ever cure correctly . To build up a blank to finish sized can be done . I've done it several times .
The first blanks I made were CA blanks. What I did was drill a 5 inch deep 3/4" hole in a piece of 2 x 4 then inserted some dried rose petals and then poured in some minwax hardner and applied some pressure with a press and a bolt inside the hole to compress the material. I did that several times until the hole was full then I let it dry for several days. After that I cut off the 2 x 4 mold on the band close enough to expose the 4 sides of the blank. Then I soaked in some thin CA several times. After that you can drill and turn the blank but it will still need CA as you turn. I made several pens using this method; corn, colored wood flakes, colored rice, crushed lentils, bird seed and others but once I discovered Alumilite I stuck to it. There is is a detailed article on how to do this in the 2008 Woodturning Design magazine, Title of the article is "Phoenix Pens"
Hey Kruzzer, casting isn't all that difficult, if you have the patience. I think that using a good medium (PR or Alumilite, Silmar, etc), having a pressure pot, but that is not absolutely necessary. Take a look at Grub32's You Tube videos where he uses a drill press to shake the bubbles out) He gives a lot of good hints on casting PR.