Just when the foodiverse grew weary of molecular gastronomy and its requisite gimmickry, bar wizard Dave Arnold stepped up to the centrifuge at Booker and Dax and made kitchen chemistry trendy again. But mad-science cocktails come at a double-digit price; for home experimentalists, there’s Molecule-R’s Cocktail R-Evolution molecular-mixology kit ($59.99 at the Brooklyn Kitchen, 100 Frost St., at Meeker Ave., Williamsburg; 718-389-2982). Equipped with lab tools and food additives like xanthan gum and soy lecithin, spirit tinkerers can learn from a 30-recipe DVD how to fashion blue-curaçao foam on the rocks, as seen here; a gin with tonic-spiked orbs; and even quivery mojito bubbles.