Which statement about reversible hydrocolloids is incorrect?

The material being referred to in the context of reversible hydrocolloids is primarily composed of agar, which typically consists of about 4-5% agar and 95-96% water. Therefore, the statement about it being 85% agar and 15% water is incorrect, as it overstates the concentration of agar in the hydrocolloid mixture.

Understanding the composition is essential because it directly affects the properties and behavior of the hydrocolloid when used for impressions. Proper handling and preparation of reversible hydrocolloids are critical in dental procedures to ensure accurate and effective impressions.

The other statements showcase characteristics that are indeed true for reversible hydrocolloids. They can be reused since they become fluid again when reheated, they require cooling to set properly, and they are typically used in special trays designed to hold the material firmly and uniformly in place during the impression process.