Introduction
[Gems of Science] attempted to produce synthetic rubies using the flux method in a household oven. A mixture of molybdenum oxide, chromium oxide, and aluminum oxide was used to incorporate the Cr3+ ions that give the aluminum oxide structure its red color.
Developments
The charcoal later added to the mixture reacted with the molybdenum, ruining the first batch, while silica-containing crucibles resulted in the formation of only very small crystals.
After the pure alumina crucibles broke, second-hand platinum crucibles were used instead.
Details
Once the rapid evaporation of the flux was balanced with additives and temperature cycles were applied, first small rubies and then larger ones measuring up to 10 mm were produced. However, the specimen cut for a ring was found to contain pockets of flux trapped inside the crystal.