We recommend that a small amount of Gentoo is mixed and applied to glass or aluminum as a test, to verify that the user is performing the mixing and curing processes properly.  Three performance tests can be performed to determine if the Gentoo is working as it should.  Please see testing procedures at http://tinyurl.com/gentoofaq1and the video at http://tinyurl.com/gentoofaq2.  UltraTech has typically used borosilicate glass or brushed aluminum as the standard test substrates.