Sodium Ammonia Etch and Tetra-etch/ Natrex both use Sodium to strip the Fluorine atoms from a carbon chain. To break down the Sodium however, different chemicals are used. A Sodium Ammonia etch uses Anhydrous Ammonia to break down Sodium into a state that can etch, while Tetra-etch/ Natrex use Tetrafuranapelene.
Material etched with a Sodium Ammonia etch will be bondable from 2 to 8 months depending on packaging and storage. Other methods of etching will be bondable from 4 hours to about 11days depending on process, packaging and storage.(These processes lose bondability from exposure to light and air.)
Clean up for a Sodium Ammonia etch is a simple water rinse at an ambient temperature, then air dried with fans. Other etching methods require rinses in expensive N-Butal Alchohol, Then rinsed with hot water baths.