You should avoid washing natural ropes, i.e. jute and hemp ropes, because their strength and structure suffer. Primarily wiping with a damp rag, if needed. But if the ropes get wet or you have to wash them (hand wash with water), then dry it on pulled really tight. Otherwise, the ropes may thicken.
If the ropes dry out during use (the oil transfers to the skin or clothes over time), then it is worth oiling them. Oiling is done by moistening a rag with oil and pulling the rope through it twice. As an oil, we recommend jojoba oil, because it absorbs well and does not go rancid in the same way as other natural vegetable oils.
On the other hand, if you know that the ropes need better protection against dirt, then you should wax them. The benefit of the wax is that the dirt and the water used for wiping with a damp rag are not absorbed so well inside the rope. Waxing is done by rubbing and warming the wax in your hands. Then pull the rope through your hands.
You can find oil and wax for the maintenance at:
https://shibarijerry.com/product-category/shibari-accessories/