Slack Wax is mixture of paraffin wax and oil originated from petroleum crude oil. Slack Wax oil content can range from 10% to 30%.

Slack Wax is produced during the production of Group I lube base oil. During production of Group I lube base oil, the feedstock firstly has to go through solvent extraction process to remove aromatics and the resultant product is called raffinate. The raffinate is then diluted with solvent like methyl-ethyl ketone (MEK) to lower its viscosity to improve low-temperature filterability. The diluted oil is then chilled to -10°C to -20°C. Wax crystals will form, precipitate and removed by filtration. The removed wax becomes Slack Wax.

The traditional usage of Paraffin Slack Wax is in the production of fully refined paraffin wax. And other major usage are for particle board and medium density fiberboard, cable filing compound , matches, candles, rust protective products and moisture vapor barriers.

With the continuous closure of Group I base oil plant which decrease supply, and new major applications for Slack Wax as feedstock for low sulfur fuel and Group III base oil plant, the price of Paraffin Slack Wax has since increased by a staggering 300% since early 2000s.