Is one allowed to mix in the liquid, which came out of the original mixture from sitting around.
Removing a Scab from One's Skin, Pulling Out a Non-bleeding Tooth, and Removing Warts, Pimples, etc. with a Utensil;
(Squeezing materials.) many different problems that arise with a spill on a tablecloth that has no plastic cover;
understanding the difference between tying and sewing in halacha;