When to use grease

Caustic solutions

When working with strong bases, especially hydroxides, the glass is attacked by the caustic solutions and this can result in the joints being permanently bonded together. The most common places requiring grease for using with caustics are:

• In refluxes between condensers and round bottom flasks (and any associated adapters)

• Glass taps in separating funnels (not teflon taps)

Glassware used under vacuum

Glassware that is going to be placed under vacuum, for example vacuum distillation kit, gas lines or Schlenk lines require liberal application of grease to avoid joins becoming seized. This is especially true if the joints will need to be manpulated whilst under vacuum, for example distillation pigs or Schlenk line taps.