I have two concave disks from a farm implement I wish to use to make bird baths, decorated inside & probably outside as well with some mosaic pattern of broken china, glass, beads, etc. I am looking for an adhesive that is non-toxic to birds and will hold underwater. It would be nice to leave them outside (zone 5)through the winter as well. There are so many different kinds for sale I don't know what would be best. Any suggestions? Thank you all for a wonderful site.