Please read the airframe and engine manufactures manual for the aircraft YOU operate. Do not listen to crew room myths.
"It requires far less heat to prevent the formation of ice than it does to remove ice once it has formed."
De-Icing Procedures.
In the event of ice actually forming in the carburettor, use the following de-icing procedures, in sequence.
1. Place mixture control in Auto-Rich.
2. Apply full caburettor heat. Hold fully on for 30 seconds or until carburettor air temperature rises to 38 deg C.
3. Adjust heat controls to maintain 32 deg C carb air temperature.
In the event of ice taking such a hold that 38 deg C air temp cannot be maintained, then -
4. Carburettor heat full cold.
5. Alcohol ON for one minute.
6 Alcohol Off.
7. Carburettor heat ON to maintain 32 deg C.
If the alcohol has failed to remove the ice, it can be cleared, as a last resort, by causing the engine to backfire, as follows -
8. Place carburettor heat control full cold.
9. Throttle to fully open.
10. Move the mixture control slowly towards Idle Cut-Off until engine backfires.
11. When ice has cleared return engine controls to normal settings and maintain 32 deg C air temperature.
The drastic procedure of leaning the mixture to the point of engine back firing, in an effort to dislodge throttle ice already formed, is only employed in extreme emergency.
N.B. When using this procedure carburettor heat controls must be in full cold position, otherwise damage to the control shutters will result.
The old girl would actually backfire itself if the carby got too choked with ice. That, combined with the ice flinging off the props and hitting the side of the fuselage was enough to sometimes arouse the F/O
These are laid down procedures for (some) radial engines. DO NOT try them if they are not authorised for your aircraft.