Robust glass is a non-tradeable resource created by melting Red sandstone in a Robust glass machine which can be accessed after As a First Resort.... Making robust glass from ore has no crafting level requirement and grants no experience. Players with level 89 Crafting can create potion flasks from robust glass using a glassblowing pipe to receive 100 Crafting experience. While the assist system can not be used to craft the flasks, it is possible to use temporary skill boosts, from as low as level 83 Crafting. it is recommended to turn the ore into the glass first before you attempt this to make the most use of the boost.

Soda ash and buckets of sand are not required to make robust glass.