A method includes flowing a hydrating liquid in an extensional flow regime through an elongated passageway of an extender, wherein a flow rate of the hydrating liquid and a diameter of the elongated passageway are sufficient to achieve a Reynolds number of 20,000 or greater. A hydratable additive is added to the hydrating liquid in the elongated passageway to produce a mixture comprising the hydratable additive that is at least partially hydrated.