Other methods involve absorption onto beads coated with an absorbent material and filtration. Soy fabrics are moisture absorbent, anti-bacterial, and UV resistant. Nylon is less absorbent than wool or cotton. In 1986, thin diapers made with absorbent gelling material were released. High frequencies are passively shielded and damped by radar absorbent material. The fiber is very strong, absorbent, and dries faster than cotton. Another principal use is as a drying agent or absorbent. In an absorption refrigerator, a suitable combination of refrigerant and absorbent is used. A gradient between the absorbent and the liquid is essential for imbibition. Bentonite is used in industry and emergency response as a chemical absorbent and container sealant. The single-effect absorption cycle uses water as the refrigerant and lithium bromide as the absorbent. One major use is as an absorbent in surgical dressings. This is more common with darker hair colors and persons with dry absorbent skin. In front they had a rubber collar that was clamped around the absorbent canister. It can be reduced by desiccating or baking the chamber, and removing absorbent materials.