Start with fully frozen seedless grapes and a blender whose instructions permit ice crushing. The short preparation estimate begins after the grapes are frozen; it cannot turn a fresh bunch into slush in ten minutes. If you are freezing grapes yourself, wash and prepare them first and leave the full freezing allowance before the time you want to serve.
Use short pulses before the longer blend, stopping the machine to scrape as its instructions require. Have both large glasses and spoons ready, since the texture softens while it stands. Do not force a household blender beyond its load or ice instructions. If you need several rounds, plan them separately so each pair of drinks can be served promptly.
Timing and servings are estimates. Equipment, ingredients and portion sizes affect the result.
