Ain Eebud b’ochlin d’oraisa. However, the Rabonnon forbade preserving food by means of salt. This gezaira extends to making salt-solutions as well. You are allowed to make only a small amount of salt water. This is because it’s evident that your intention is to spice your food right now, not to preserve it for later. (ShA 2 – MB 8, 9)
Even when making a small quantity of salt water, it must not meet the ratio of 2 parts salt/ 1 part water. (ShA 2)
If you want to make a large quantity, you can add some oil into the salt (or into the water) **before** mixing the salt into the water. (MB 10)
**Salting vegetables**. Any vegetable that is normally salted has restrictions. You are not allowed to salt 4 or 5 cut pieces together unless you add vinegar or oil immediately afterwards. (ShA 3 – MB 14)
If you want plain salt, you can dip each piece into salt and eat them one by one. (ShA 3)
There are no restrictions regarding salting eggs for use on Shabbos. Do not salt eggs or meat to preserve for after Shabbos. (ShA 3, 5 – MB 21)
Grinding pepper in the normal way is the melacha of Tochayn. To grind pepper in a permitted way you must make two changes : instead of a pestle use the handle of a knife and instead of a mortar use a bowl or the table. Even still, you cannot grind for after Shabbos use. (ShA 7 – MB 23, 24, 25)
It is forbidden to chop up peppercorn with the blade of a knife. (ShA 25)
Grinding coarse salt has the same halachos as pepper. (ShA 8 – MB 27, 28)
You are allowed to crush a sugar cube as long as you don’t use a special grinding kli. (MB 30)
Ready-to-eat foods that do not grow from the ground are not subject to Tochayn. e.g. cooked meat, cheese. (ShA 9, 10)
You aren’t allowed to use a cheese grater on Shabbos (ShA 10)
You aren’t allowed to grind things with your teeth unless someone will be tasting it (i.e. yourself or a baby). (MB 36)
You are allowed to water harvested vegetables to prevent them from wilting. (ShA 11)
Potted plants are not allowed to be watered. (MB 37)
Chopping a vegetable into small pieces is Tochayn. Since we do not know how small is “small”, cut them into pieces a little bigger than usual. (ShA 12 – BeH “ham’chataych”)
You are allowed to make bread crumbs and matza meal – just not with a specialized utensil. Since they were originally ground flour, we apply the principle of “ain Tochayn achar Tochayn”. (Rama 12 – BeH “l’farayr”)
The Rama is lenient to chop up vegetables finely to eat right away – similar to the laws of Borer in Siman 319. If you see someone relying on the Rama, do not reprimand him. However, you should conduct yourself to cut the pieces bigger than usual. (Rama 12 – MB 45)
Even those who rely on the Rama should not chop the vegetables until the men leave the shul and the seuda will begin shortly. (MB 45)
And even those who rely on the Rama should not use a specialized chopping utensil. Therefore do not finely chop the onions into the herring using a “hak-messer” specially suited for the job. Rather use a regular knife. (MB 45)
Crumbling a dirt clod is Tochayn. (MB 45)
Making sawdust or metal filings is Tochayn. (MB 45)
Cutting logs into lumber is Mechataych. (MB 45)
Squeezing honey out of a honeycomb is Mefarayk. (MB 48)
The melacha of Losh is the act of stirring liquid into solid and thus forming a **thick mass**. Some poskim hold that merely pouring the liquid into the dry solid is already Losh. The minhag is to be machmir for this. (ShA 16 – MB 64 – ShaH 324:11)
Before Shabbos add a little bit of liquid to start the Losh process. (A few drops that do not wet everything is not enough.) Then , on Shabbos you can add more liquid. (ShA 16 – MB 65)
Stirring and kneading the mixture is also Losh unless you make a shinui – that is kneading a little at a time. Other thick mixtures that normally need vigorous mixing can be mixed gently as a shinui. (ShA 14, 15 – MB 58)
When making a **thin** mixture, Losh does not apply d’oraisa. All agree that you may add the liquid at first on Shabbos. However, do the shinui of mixing a little at a time. (MB 66, 44)
Another legitimate shinui for a **thin** mixture is to reverse the order. That is, put in the liquid and then the solid. Add another shinui by mixing with your finger or shake the container – don’t use a spoon. (Rama 16 – MB 66, 68)
Let’s say a sick person cannot chew the bread. You are allowed to crumble it for him and add liquid to clump it together a little at a time. (BeH “va’afeelu”)
Spitting or urinating on sand that does not belong to you is allowed. (MB 57)
When pushing sand onto a puddle of urine, push enough sand to ensure the Losh action is not apparent. (MB 57)
If you forget to pour the vinegar into the chopped horseradish before Shabbos, make a thin mixture and reverse the weekday order. To mix it, shake the container. (MB 68)
Losh does not apply when pouring liquids into big pieces of vegetable (lettuce). (MB 68)
Diced vegetables are subject to Losh. If you can’t add the liquid before Shabbos you can be maykil to add the liquid on Shabbos – relying on the shitta that merely pouring in the liquid is not Losh. Make two shinuim – reverse the order and mix by shaking the container. (MB 68 – ShaH 84)
When Seder night falls out on Shabbos and you did not add any liquid to the charoses before Shabbos, it’s best to make a thin mixture. (MB 68)
You aren’t allowed to beat raw eggs on Shabbos – it appears as if you want to fry them. (MB 68)
Mixing solids into drinks is not subject to Losh at all. (ShA 17)
Under the ban of taking medicine on Shabbos is **making** medicine on Shabbos (even without a melacha).. (ShA 17 – MB 70)
If a certain “remedy” is enjoyed even by some healthy individuals – it does not appear like refuah and is permitted. For the same reason, you may hide medicine in food and eat it normally – it does not appear as refuah. (ShA 18 – MB 72)
Certain medicines need to be taken for 3 days in a row, otherwise the patient can be in danger. If Shabbos is one of those days, he may make the medicine and take the medicine on Shabbos. (ShA 18)
Smoothing out wax and tar is the melacha of Memachayk. Memachayk on food is only d’rabbonon. (MB 80, 81)
Spreading food evenly onto bread is allowed. Even to spread out an apple topping or mashed potatoes to make the food look enticing is okay mayikar hadin. (If you are machmir you will get a beracha.) Memachayk on food is only ossur if you can't eat it otherwise. (Rama 18 – MB 81, 82 – BeH “b’maachal”)
Peeling garlic, onions, nuts, almonds, and apples is Borer unless you will be eating the fruit immediately. Even though you are removing the pessoles from the ochel, it’s muttar since there’s no other way to get to the inside. (Rama 18 – MB 84 – BeH “l’klofe”)
The Pri Megadim asks – most people eat the apple skin so it should be allowed to peel the apple (and likewise the turnip and carrot) even to leave for later. (ShaH 97)
If you open a plum and throw away the hard pit it is Borer unless you eat the fruit right away (or at least during that same meal). The same goes for apples. (MB 84)