Vases can be difficult – because of the way the printer operates anything other than a single player print tends to show surface marks – either a visible join if the head moves up at the same point on each circle. or more irregular marks if the slicer generates a path where the vertical movement is more random. The marks are particularly visible if printing a shiny surface. Slicers have a ‘vase mode’ to overcome this, but it operates by following a spiral path, and the walls can only be one layer thick, which reduces the strength and also makes it likely that it will not be completely watertight. The vase in this picture was printed in vase mode, and looks good, but it does tend to leak slightly. Some people report that altering slicer settings can help, or they use a larger diameter extruder to print this type of object, but changing the extruder for different jobs is quite a job, and not one I would undertake, and the alternative of a second printer with a larger extruder is not practical for me (though at least one person on the web does do this!). The last possibility I plan to try in the next day or so is to fill the vase with liquid resin after printing, then immediately empty it. This won’t do much if anything fro the strength, but it may make it more watertight.
This is only a short version of the things that can be tried, but so far none of the things I have tried have solved the problem, so I await the results of the test with some resin with interest.