We have not been able to personally test every last one of Weldbond's claims, but our store customers tell us it's "the BEST glue EVAH!". (Our store customers have Boston accents.) They tell us it's especially great for mosaics.
According to Weldbond: "This glue is non-flammable, non-toxic & dries clear. It can also be used as a primer for porous surfaces. It is highly water-resistant and impervious to petroleum, oil, grease, salt, moulds and fungi, alkali's, and weak acids. Weldbond withstands all climatic conditions after curing. It is non-staining and will not become brittle with age. Weldbond is also used by Nasa for Escape Suites on space shuttle flights." (What does that even mean? Escape Suites?)