Is it permissible to add water to milk when making yogurt intended for sale?

It is permissible to sell yogurt to which water has been added if its production cannot be completed without it, for mixing water with milk to extract butter is an improvement, not a deception. However, if its production can be completed without adding water, then it is not permissible to sell it, unless the amount of water added is known and clarified to the buyers. This is because not knowing the amount of water makes it an unknown sale and involves gharar (excessive uncertainty), and the Prophet, peace and blessings be upon him, forbade the sale of milk mixed with water if it was for sale.