The basic constituent of reversible hydrocolloid impression material is:: (A) Agar, (B) Alginic acid, (C) Gelatin, (D) Alginate
Answer is A. Composition
Agar, a polysaccharide extracted from certain types of seaweed, is the main active ingredient in the material, while water is the major constituent in the agar impression material. A small percentage of borax is added to strengthen the gel. Since borax is a potent retarder for the setting of gypsum, an accelerator such as potassium sulfate is added to counteract the effect of borax.