Delayed viscosity well treatment methods and fluids

A well treatment method includes forming a well treatment fluid by combining ingredients including a polymer, a crosslinker, an acidifying substance, and a base fluid. Crosslinking increases viscosity of the fluid during a development time. A pH decrease is controlled during the development time using the acidifying substance. The method also includes delaying the development time of the viscosity increase by controlling the pH decrease. A well treatment method includes forming a well treatment fluid by combining ingredients including a hydratable polymer, a crosslinker, an acidifying substance, and a base fluid. The method includes delaying development time of a viscosity increase by controlling a pH decrease without adding further acidifying substance after combining the polymer, crosslinker, acidifying substance, and base fluid. A well treatment fluid formulated with ingredients include a base fluid, a polymer, a crosslinker, and an acidifying substance. The acidifying substance is configured to delay development time.