Yes you can definitely wash your face post treatment but just do it very gently. Do not use any retinols, acids, vitamin c or topical exfoliates for at last 3 days post treatment.
After Voluma injections, the product may be moldable for a few hours. We usually recommend being gentle to the area. The questions remain of what is 'normal'? if normal means gentle soap with care not to apply pressure to the injected areas then yes, it's safe.