1. One who sorts food from refuse, or if there were two food types placed in front of him and he sorts one from the other - with the aid of a sifter or strainer he is chayav (liable); with a cone or dish he is patur (not liable) but it is forbidden to do so, but if he sorts it with his hand in order to eat it immediately it is permitted. RAMA Whatever one separates for a meal he is immediately about to eat, is called “for immediate use” (Heb. לאלתר). [Hamagid; the R"i; Beis Yosef; Tur; the Rosh] Even when others are eating with him it is permitted. [Tosefos] Therefore it is permitted to separate the (good) leaves of a vegetable called lettuce from the moldy ones that one requires for the upcoming meal. [Beis Yosef Siman 321]
2. One who sorts food from waste by hand for later use, even for later on that day, is as if one is sorting for storage, and is chayav.
3. Two foods that are mixed may be sorted from each other and one may place (the other food in order) to eat immediately. RAMA: Two kinds of fish are categorized as two types of food and one is therefore forbidden to sort one from the other unless done by hand to eat right away. This is even if the pieces are large and each one is noticeable by itself. If however the pieces are all one type even if one sorts the big pieces from the small it is not called sorting. Even when two types are mixed and one sorts both together the big from the small or vice versa it is permitted because one is not sorting one type from another. [Terumas Hadeshen]. If one sorted and left it for later, even for that same day, for example in the morning in order to eat in the afternoon, one is chayav.
4. One who separates waste from food even with one hand is liable. RAMA: Even if there is more food (than waste) and it is more arduous to remove the food, nevertheless one must not remove the waste even if eating is imminent. (Beis Yosef).
5. One who separates Lupine from within its waste is liable because its waste sweetens them when cooked together, and it appears as if one is removing the waste from the food.
6. It is forbidden to separate through rubbing, yet one may rub with a modification; a small quantity with the tips of one’s fingers. RAMA: Even though one is separating the food from the stalks; but since it is done in a backhanded manner in order to eat it, it is permitted. Yet there are those who are stringent [Mordechai; Ra"n] and therefore it is forbidden to shell almonds or big nuts from their green shells (Mahar"il). It is correct to be stringent because it is possible to eat without shelling.
7. Food peeled before Shabbos must not be sifted with a cone (which Rashi explained to be a utensil whose one end is wide and the other is in the form of a spout. Legumes are inserted into the wide end, and shaking causes the food to roll out the spout and the refuse to remain inside) or with a plate (a large plate), or with both hands. One may sift using one hand with all one’s strength.
8. It is forbidden to soak Karshinim i.e. to soak them with water in order to remove the refuse. It is also forbidden to rub the Karshinim with one’s hand (when already in the water) to remove the peel because it is akin to borer. However one is permitted to place them inside a sieve even though the refuse slips out between the slits in the sieve.
9. It is forbidden to put dregs inside a strainer even when the strainer was hanging in place before Shabbos; but if the dregs were put inside before Shabbos it is permitted to pour water over them until the water becomes clear.
10. Clear wine and water may be filtered through a strainer RAMA: even if there are thin slivers of wood because it is drinkable as it is (Sma"g), but not through garments because of laundering, however wine and other liquids are permitted. If the liquid is opaque, be it wine or water, it is forbidden to strain. According to the Rambam it is forbidden to filter through a strainer whether clear wine or water and only clear liquids are permitted through garments, not opaque liquids. A barrel of wine directly from one’s vineyard may be stirred and poured through a garment as long as it is bubbling (it looks as if it is boiling).
11. When straining wine through a garment one must take care not to form an indentation in the cloth to collect the wine, because there must be a deviation from a weekday.
12. Whenever a garment is permitted to be used for straining wine, an Egyptian basket (made from types of reeds) may be used as well. However, one must take care not to raise the basket more than a tefach from the bottom of the Keili in (order to deviate from a weekday.
13. One must not wedge straw and splinters into the mouth of the Keili that is used for pouring wine from a barrel, because it makes a perfect strainer.
14. It is permitted to pour slowly from one Keili to another as long as one ceases pouring when he notices that it stops flowing and begins to trickle from within the waste. If one does not cease, the trickling will be a noticeable act of separating. (It is permitted to raise the Keili onto something to enable the wine to flow more freely). (Rokeach; Beis Yosef).
15. A strainer that has mustard placed inside it to strain may have an egg put inside even though the yolk falls through with the mustard and the albumen remains in the strainer.
16. Water with worms may be drunk through a cloth on Shabbos because Borer and Meshamer only apply when separating prior to eating or drinking, but while actually drinking it is permitted to block the refuse from entering one’s mouth because it is not similar to the Melacha at all.
17. Churning (extracting butter from milk) is a Toldah of Borer and therefore although one may put sesame and nuts into honey he must not churn them with his hand (see Siman 340:11). RAMA: One who spits into the wind on Shabbos and the wind disperses the saliva, is liable for Zoreh – Winnowing. [Mahar"il in the name of Or Zarua; Yerushalmi]