The legal term for the process of freeing slaves was manumission. Depending on the colonial power at the time manumission took various forms and had different processes. Manumission also granted different degrees of social freedom for former slaves.

It should be noted that it wasn’t a practice that was pursued regularly. More often than not it wasn’t simply done out of the kindness of the owner’s heart. After all, they were losing a part of their workforce. No, for an owner to release a slave from their service there was usually some incentive to do so—a fail-safe for losing a worker.

Terms of Manumission

Since it was often up to slave owners to be willing to part with a slave they often came up with the terms of freedom. Whether it was a set price to purchase their freedom (usually the case since it was easily manipulated) or after a certain amount of time in service, the owner made sure they were able to get something out of the deal.

The main exception to this was aged slaves. Once they became too old for heavy manual labor they could end up being released. Slaves who worked in close proximity of the owner while proving themselves to be useful to the family usually had higher chances of being released.

Even with freedom, slaves often ended up either back in the service of their former master or doing the same work. This was because job opportunities were slim and slaves were usually trained to specific skills. Even with marketable skills, a free slave could find themselves on another plantation working for a pauper’s pay.

There are some slaves who managed to make a life for themselves after being released. In a few cases the freed person would start their own farm, own some slaves of their own, or take up work in their trades.

Advantages For Slaveholders

The social advantage of manumission was that slaves worked towards the goal of potentially being released. Since most were illiterate and wouldn’t know the colony’s or state’s laws regarding manumission, slaves could end up working towards freedom that likely wouldn’t come. There was also a provision for slaves informing on other slaves who were planning rebellions or escapes.

In addition, there was a sense of “doing a good deed” in freeing a slave.

There was the legal fail-safe of their freedom being determined by a governing body or official. This played into merit-based manumission. The other method of freeing slaves pre-Emancipation was through a will as George Washington and Thomas Jefferson did. In Jefferson’s case only five of his 135 slaves were freed while the rest were sold.

REFERENCE
-http://www.history.org/history/teaching/enewsletter/volume3/february05/manumission.cfm