Lead crystal is glassware of higher lead content, either die-cast or manually blown and faceted. The content of lead makes the glass softer, enabling to polish and engrave it. The lead glass is of higher shine and the light reflects on the surface in all rainbow colours.
According to EU standards a product with less than 4% PbO2 content is glass. A product with more than 10% content may be called as crystal glass (lead glass). Lead crystal is a product with more than 24% PbO2 content. But according to US standards a product may be called lead crystal already from 1% PbO2 content.