True tung oil is a natural substance but will dry hard. Be careful with tung oils as woodwork finishes sold as "tung oil finish" is not only tung oil. There are other chemicals in there. Personally I would not use it on a pipe. Look up tried and true wood finishes. Their original is a very good product, totally natural, with no driers. you could eat it. It is commonly used as butcher block finish. you can see examples of this finish on wood if you look up Christian Becksvoort woodworking. He recommends tried and true. Ive used it on furniture and if you follow the application instructions it provides an exceptional warm natural look and feel. Another option would be mineral oil and beeswak mixed, which is also a common butcher block "finish". Personally I would just stick with wax though.