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.

seen from Malaysia
seen from United States
seen from China

seen from Germany
seen from Iraq
seen from Germany

seen from Germany

seen from Italy
seen from Malaysia

seen from Netherlands
seen from Netherlands

seen from United States
seen from Malaysia

seen from United States
seen from Germany
seen from United States

seen from India
seen from China
seen from United Kingdom
seen from India
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.