Sweat runs down Adan Marin's wrinkled face as he blows into a blob of molten glass, creating a perfect, delicate sphere within the blue and orange flames of his torch. Marin is one of the godfathers of the glassblowing trade in the Mexican village of Tlalpujahua, which makes tens of millions of ornaments each year to decorate Christmas trees in American and Canadian homes. Even mid-winter, the sun shines strong in this village in the western state of Michoacan. But it might…