Handling Resin Blocks

Abstract

Epoxides have excellent sectioning properties. Glass or diamond knives can be used and for semithin sections the knives can be used dry. 0.5-1 µm sections can be picked up in the jaws of fine forceps and floated on to the surface of droplets of distilled water on glass-slides. They are dried down with gentle heat (< 60°C, 2-24 hours) and, without adhesive, will generally stick firmly to the surface of the glass. Problems with wrinkling or creasing can sometimes be alleviated by wafting chloroform on a cottonwool bud over the section while it is on the water droplet, prior to drying down. The hydrophobic surface of glass-slides “subbed” with chrome-alum gelatin (Pappas, 1971) is particularly useful for creating very rounded water droplets with a high meniscus. When warmed the reduction in surface tension is often strong enough to pull out wrinkles without recourse to organic solvents. Gelatin is digested by proteolytic enzymes and, therefore, should be avoided if section proteolysis for immunocytochemistry or in situ hybridisation is envisaged.