Milliput Standard Yellow GreyMilliput is a epoxy putty used by modellers for all kind of applications. Each package contains two separate bars, one of which is a hardener. Upon mixing an equal quantity of each different bar the material starts to harden, and hardens fully in 90 minutes, after which it can be carved, sanded, drilled, and sculpted over. If you are interrupted while you are mixing Milliput, you can put the Milliput into a deep freezer until you can get back to work.