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- Merakaid is the action of sifting and removal of unwanted matter from a mixture using a sifter, sieve, or the like.  This Melacha is similar and overlaps with the halachot of Borer and Zoreh, see there for more practical examples.
- One can only violate this melacha using a sifting or straining device. 
- One of the practical issues that come up by miraked is the issue of filtering liquids on shabbos. see footnote 
- Using a strainer or colander, one may not separate noodles from soup, vegetables from a pot of water, or coleslaw from salad dressing. 
- One may not sift out clumps of powdered baby cereal from the finely ground cereal, clumps of sugar from finely ground sugar, or clumps of salt from finely ground salt. However, in these cases it is permissible to crush the clump. 
- One may not sift out clumps of confectioner sugar from powdered confectioner sugar, however, one may use a sieve to scatter the confectioner sugar on a cake. However, since a sieve is Muktzeh, if one has a non-Muktzeh scattering utensil in the house, one should use that. 
- According to Ashkenazim, one may not use a salt shaker which has rice kernels in it, placed there to absorb moisture, because in using the shaker one will be separating the salt from the rice.However, according to Sephardim, it is permissible to use such a salt shaker.
- If a tea kettle has a mixture of tea and tea leaves and at the spout of the kettle there is a mesh wiring that separate out the leaves, one may pour from the kettle as long as the tea leaves have settled to the bottom of the pot and aren't being separated from the liquid going through the spout. However, once the flow comes to a trickle one shouldn't pour from the kettle because in doing so one would be separating the tea from the tea leaves using a strainer. 
- A child who understands the holiness of Shabbat should not be let to play with a sifting toy which sifts out pebbles or dirt from the sand.
- Draining the dressing from salad using a slotted spoon is a violation of Merakaid.
- 39 Melachos (vol 2, pg 507)
- 39 Melachos (vol 2, pg 507)
- * The rashba (139b) explains that there are 3 levels of liquids. The 1st level is when something is tzalul (clear). This means most people would drink it the way it is and you are straining it to make it better. Therefore, even when using a real strainer it would still be permitted. The 2nd level is where most people try not to drink it that way, but there are people who would. In this case, we allow you to strain it using the handkerchief which serves as some sort of shinuy and this is the case of the mishna. The 3rd level of liquid is where no one would drink this liquid in its current state and when this is the case any straining would be prohibited.
- The Gemara in shabbos (138a) discusses the laws of mishamer. Mishamer is the issur of straining on shabbos. The gemara asks what av melachah must one use as a warning when he sees someone violating mishamer. Rabah says mishamer is a law in borer because you are taking ochel from psoles. R’ Zeira holds it is a law in miraked because the psoles is on top of the ochel. What are they arguing about? Rashi (138a) explains that everyone agrees that a warning of miraked would work and this is just a debate in whether borer is a good warning. Tosfot (73b) disagrees and says Rabah argues on whether miraked would work as well. If one were to warn from miraked, people would think he is kidding and not take his warning seriously. Many ask on Tosfot, how can Rabah only think borer would be a good warning, what is the difference between mishamer and miraked? The Chidushei Haran in shabbos (137b) explains that miraked is different from mishamer because it only applies by solid foods. The Biur Halachah (319:9) answers that miraked is different because it is something which is a process and does not happen immediately but mishamer happens instantaneously.* The mishna in shabbos (139b) says one may use a handkerchief to strain liquids. In the gemara, Zieri says one may use a real strainer to strain clear liquids, but he may not do so with cloudy liquids. We have to understand what Zieri is adding in the gemara. The chidushei Haran (139b) thinks that Zieri and the mishna are discussing the same case. When using a handkerchief there would be more of an issue because it could lead to squeezing liquids out of a cloth. However, to strain with a strainer would certainly be permitted. This is true when we are dealing with clear liquids. The rambam (8:14) feels that regardless of what kind of liquid we are dealing with, using a real strainer is always prohibited. Zieri was not discussing a real strainer, he was talking about a handkerchief and he was being stricter than the mishna. A strainer will always be prohibited. * The Shulchan Aruch (319:10) concludes that straining clear liquids in a real strainer would be permitted. This would mean that using a water filter would be allowed provided that we are dealing with clear liquids. The Biur Halachah (319:10) quotes the pri migadim that if one would not want to drink the water without the filter, it may be an issue on shabbos. * If we do not assume like the pri migadim and believe that we determine whether something is drinkable based on whether most people would drink it, there is an additional factor to keep in mind. If we are in a place where drinking the tap water would be prohibited, even though many of the people in the place would drink it, it may still be an issue. Though, in the general case where the water is basically drinkable without filtering, Shemiras Shabbos Kehilchasa (3:56) writes that it is permitted to use a built-in filter or a pitcher with a filter on shabbos.
- 39 Melachos (vol 2, pg 514)
- 39 Melachos (vol 2, pg 514)
- 39 Melachos (vol 2, pg 514-5)
- 39 Melachos (vol 2, pg 515) writes that it's forbidden. He also quotes Halachos of Shabbos (Rabbi Eider pg. 196) who quotes Rav Moshe and Rav Aharon Kotler as agreeing. Shemirat Shabbat KeHilchata 3:66 writes that it's better not to. Sh"t Az Nidberu 2:14, 4:23 however, is lenient
- Yalkut Yosef (Shabbat vol 3, pg 307), Daily Halacha by Rabbi Eli Mansour
- 39 Melachos (vol 2, pg 519)
- 39 Melachos (vol 2, pg 516)
- 39 Melachos (vol 2, pg 525)