In reality , it was sand . Sand used to make the finest glass . After the war , the Barcid king had ordered that no glass was to be given to outsiders at any cost . Thus , over the years , glass had become scarce and the process of glass making lost to the world .
Question: What may be the reason glass has become scarce and the process of making glass making be lost to the world ?
The answer to the above question:


The Barcid King did n't want the glass from his sand to go to outsiders .