There are various adhesives available today each of which has its advantages.
The strongest readily available adhesive, it can be diluted to the required strength, and dries to form a flexible product. It can provide a degree of moisture resistance if your finished product is to be used in a bathroom etc.
A cheap adhesive, traditionally associated with papier-mâché making, produces a strong less flexible finished product than PVA. Most wallpaper pastes contain anti-fungicides so rubber gloves should be worn when handling the papier-mâché.
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