Glassteel

The glassteel spell turns normal, non-magical crystal or glass into a transparent substance that has the tensile strength and unbreakability of actual steel. Only a relatively small volume of material can be affected, a maximum weight of 10 pounds per level of experience of the spellcaster, and it must form one whole object. The Armor Class of the substance is 1.

[Player's Handbook]

School: Alteration
Level: 8
Rarity: Common

Range: Touch
Components: V, S, M
Duration: Permanent
Casting Time: 8
Area of Effect: Object touched
Saving Throw: None

Material Components: a small piece of glass and a small piece of steel (consumed)