Immediately after pick up the walnuts should be washed to remove any dirt or husks still clinging to the shells. Dirt on the outside of the shells can indicate that the kernel inside may be second grade. Washing at this point of the harvest is very important to maximise the financial return on the crop. Washing techniques include:

NB. Do not wash the walnuts in an onion bag and then leave the walnuts out to dry while still wet inside the bag. The same is appropriate for plastic buckets or any container that will not allow air to get around the walnuts - they will go mouldy very quickly and be of no value as a food item.