Tempered glass is a tier 1 rare combine (needing lapis or copper); the recipe is in the Artisan Components Volumes 5&6 rare book. You also need the rare Artisan Refining Volume 4 to refine the lapis/copper beforehand; the loam used to make the glass is a by-product of refining the lapis/copper.
http://eq2.eqtraders.com/recipes/show_recipe.php?recipe=1013
Is that the one you're looking for?