Here are the set of test tiles for lower in the kiln, for the second, hot firing (1200 centigrade). Glazing half of each tile to see if it is indeed the glaze which causes the melting, as I suspect. 

Here are test pieces in the kiln after biscuit firing; annoyingly, one piece exploded - a shame, as they were in pairs (4 colours slip + 1 base clay, one of the pair for lower in the kiln, one higher. So be it. 

Sgraffito tile of a cheerful girl, ceramic with coloured glaze

Colour test tile for green glazes. I find these tests with sgraffito scribbles more helpful than just lines or dots, and people seem to find them quite tactile, stroking and picking them up without thinking.

Colour test for orange and yellow glaze, with and without clear glaze.