Carefully remove the cylinder from the revolver: place the hammer on half cock, remove the wedge, then rotate the cylinder so that the loading lever plunger presses against the web between two chambers and use the lever to remove the barrel assembly. Then remove the cylinder. Be sure the gun is pointed away from yourself and anyone else in the room while doing this.
The cylinder is removed so that, if a chamber is ignited while the caps are being removed the ball will not reach full velocity. While it will cause damage or injury, the effect will be much less than if the ball travels through the barrel and reaches full velocity.
With the cylinder on the bench open end down, carefully remove each cap from the nipple. Once the caps are removed the probability of a chamber being ignited is greatly reduced, but you still need to exercise caution. Next, remove each nipple with the nipple wrench. Hold the cylinder over a towel or large vessel to collect the ball and powder. Insert a small wood or metal dowel (3/16" diameter) into the nipple hole and slowly but firmly push the powder column and ball out of each cylinder.