The Parting of Lot and Abraham is about their literal parting - Abraham took his family to Canaan, as God wanted him to, whereas Lot went to Sodom, and defied God's wishes. Now, having this in mind, maybe this mosaic does symbolize B. heaven, as Abraham and his family would go to heaven eventually, because they obeyed God's orders and wishes.
Binders used for watercolor paints commonly are natural gum or synthetic glycol,
tempera is usually glutinous material such as egg yolk
