The Difference Between Glass Cullet and Glass Slag

Iron Ore

• Glass slag has iron mixed into the composition of the glass as it is being shaped. This adds white streaks to the coloring of the finished piece. The glass blower shapes the glass to take advantage of the streaking to create patterns in the glass that are not on the surface and in danger of wearing off, but run through the glass itself.

Recycle Sources

• Glass slag is typically used to make lamps, knobs and other decorative items. Glass cullet is only created from recycled glass bottles. The bottles are broken and the pieces tumbled and polished to remove sharp edges.

Weight

• Glass slag is heavier than glass cullet pieces as they are made from discarded decorative objects that have a thicker glass body than bottles. When a retailer offers "glass rocks" for landscaping, they are usually referring to glass slag. Glass "sand, gravel or pebbles" refers to glass cullet.

Color and Opacity

• Both forms of recycled glass have even coloring. Glass cullet pieces will be more transparent, as glass bottles are transparent and the colors are muted. Glass slag is more opaque, streaked through with white and the colors are stronger.