I remember hearing a PBS documentary make a claim that the babies of slaves on George Washington's Mount Vernon went naked in winter. I have been trying to verify, or even get a good citation, for this fact. (Any web reference to conditions of slaves owned by the Founding Fathers is also of interest.)
The material aspects of life for slaves at Mount Vernon--things like their quarters, clothing, food--were very similar to the way things were done on other large plantations in 18th century Virginia (places like Monticello or Sabine Hall). In the case of infants, mothers at Mount Vernon were given a new blanket at the time of the birth and baby clothes of some type were provided, as well. For sources on slave life at Mount Vernon, we suggest the following:
Delano, Marfe Ferguson. Master George's People: George Washington, His Slaves, and His Revolutionary Transformation. Washington, DC: National Geographic, 2013.
The George Washington Digital Encyclopedia: http://www.mountvernon.org/encyclopedia#Slavery
Schwarz, Philip J., editor. Slavery at the Home of George Washington. Mount Vernon, VA: The Mount Vernon Ladies' Association, 2001.
George Washington had in total about 300 slaves at the height of his slave-owning career, but only about 150 were directly his, the others being indirectly his since they were acquired through family connections and so on. I think Martha Washington brought many or maybe most of them to the marriage--a lot of George's wealth (land, etc.) came from marrying Martha.
In his will, Washington freed the approximately 150 slaves that were his to free. The others were not legally his, so he couldn't. That he, as a Virginia landowner and wealthy individual, did this was rather unusual and is noteworthy.
My source for this is Ron Chernow's "Washington: A Life." Here's an interview about the book where he mentions the above numbers of slaves: https://www.youtube.com/watch?v=8KLybZDahzQ
In other words, George Washington was far from the worst master a slave could have had. He was very much invested in the slave-owning soclal order that put him at the top of the food chain, but he did recognize slaves in a more humane way, as being more than live property like horses or hunting dogs. The interview above talks about Washington's feelings toward his slaves--demanding, but not wholly inhumane.