Enfamil AR formula has added rice starch to reduce spit-up and increase a baby's feeling of fullness. However, the rice starch makes it more difficult to mix the powder into a smooth, clump-free formula. As of April 2011, the most common complaint about Enfamil AR powder on the Enfamil customer review message boards was "doesn't mix well." However, you can take steps to make your Enfamil AR powder free of clumps.
Measure an amount of boiled water (cooled to room-temperature) into a bottle that will accommodate the amount of formula you intend to feed your baby. Add one scoop of powdered formula for every two ounces of water in the bottle. Putting the powder in the water rather than pouring water over the powder lets the powder dissolve as it descends.
Cap the bottle as quickly as possible. The sooner you cap and shake the bottle, the less likely you are to get clumps. If you have a cap for the bottle, use it. If all you have is a nipple and collar, put the nipple on upside down. This will prevent the formula from clumping in the nipple when you shake it.
Shake the bottle from side to side for five seconds. Turn the bottle upside down and right-side up with a vigorous shaking motion for 10 seconds. This will allow currents to break up the clumps from multiple directions.
Let the bottle sit for five minutes before feeding it to your baby. This will help hydrate the starch, making it more liquid and helping it flow through the nipple. Do not let it sit at room temperature for more than two hours. Turn the nipple right-side up immediately before feeding.
Whisk the formula with a clean wire whisk after you let the formula sit, if you are making large quantities in advance. This is impractical for single feedings, as the whisk will not fit into the bottle, but is ideal for larger amounts of formula mixed in a larger container.
Because the formula should sit for five minutes, study your baby's hunger cues so you can begin preparing the bottle before he or she starts to cry. Wakefulness, lip-smacking and sucking on fingers are signs of hunger in a newborn. Always use sterile bottles and utensils when feeding your baby. Your baby's mouth will introduce bacteria into the bottle. If any formula remains one hour after you begin a feeding, discard it.