- Plastic resin that serves to adhere a stool sample onto a slide - Normally incorporated into the Schaudinn’s solution - Main advantage: preservation of protozoan cyst and trophozoites for permanent staining - Stool preserved in PVA can be concentrated using FECT - Modified PVA: using non-mercuric compounds such as copper sulfate or zinc sulfate (used with trichrome stain) - Disadvantage: use of mercuric chloride