Shabbat 50: Normally Set-Aside Items

In Shabbat 49, the rabbis discussed a new Mishna that teaches us we may insulate a pot of hot food on Shabbat in clothing, produce, doves' wings, wood shavings, and the chaff of fine flax, with disagreement from Rabbi Yehuda.  Of course, the doves' wings stand out, and this is discussed.  A second Mishna from Daf 49  teaches us that we may insulate cooked food on erev Shabbat with wool fleece but we can only move the fleece by lifting the cover and the fleece will move by itself.  There is argument about what can be done if the fleece moves incorrectly once there is movement.

In today's daf, the rabbis continue this last conversation.   What is the intention when one placed the fleece on the food? Where did the fleece come from, a merchant's shelves or one's home, already prepared to use?  

The rabbis then consider how we would permit the use of items that are normally set-aside on Shabbat.  An example is the hard branches of a palm tree first designated as fire wood and then used for sitting.  Must the branches be tied at a certain time?  Other examples include going into the public domain with combed wool covering a wound as long as they are dipped in oil or tied with twine.  There are even some exceptions to this halacha.  Cleaning utensils is fine on Shabbat using agents like natron and sand, but using cream of tartar (white earth, chalk or limestone) is not allowed because it will smooth the utensil.  One of the more interesting examples is bringing soil into the home on Shabbat so that excrement and other filth can be covered over the day.