What was found
PRIOR TO LIFT OFF, TURNED BLEED AIR HEAT AND VENT ON TO DEFOG WINDSCREEN. DURING THE TAKEOFF AND CLIMB OUT PHASE OF FLIGHT, A BURNING ODOR AND VISIBLE SMOKE WAS DETECTED IN COCKPIT. TURNED OFF THE BLEED AIR, AS WELL AS OPENED FRESH AIR VENT. ABORTED FLIGHT AND ENTERED DOWNWIND FOR RETURN TO BASE. ODOR AND SMOKE DISSIPATED SHORTLY AFTER A NORMAL LANDING. ACFT OUT OF SERVICE. INSPECTED ACFT AND FOUND RESIDUAL COMPRESSOR WASH SOAP IN THE MIXING VALVE. EXCESS SOAP REMOVED FROM THE VALVE WITH NO FURTHER DEFECTS NOTED.