What is Mt. Redoubt's magma composition?

Well, this is kind of tricky, because the mountain has created a broad diversity of rocks: andesite, basalt and dacite, with relatively silicic andesite dominant in recent eruptions. This is kind of acid magma, which is less hot and more viscous than basic magma, like in Hawaii for example. If you want an indication of the viscosity of lava, just check the eruption: if it's a big bang, it's likely acid. If it just flows, it's probably basic, and less viscous