Baristas always recommend prewarming porcelain cups. Thats because a cold cup can reduce the temperature of freshly prepared coffee by as much as 10 degrees as soon as the beverage hits it. Ensuring that the cup is the right temperature is essential for helping the coffee aroma develop fully.JURAs practical, small cup warmer is the ideal partner to any automatic coffee machine. The cup warmer S keeps the cups inside it consistently at a temperature of around 55C. The cover also prevents heat loss, saving energy as a result.