May one make Tehina on Shabbos?
Adding water to pure Tehina: It is forbidden to make a normal texture of Tehina by placing water to pure Techina, if the Tehina did not have water mixed into to it before Shabbos. It is however permitted to add a large amount of water ]simultaneously-not drop by drop] to the Tehina and make it into a thin batter [i.e. a thinner mixture than usual], provided one does so with the two forms of irregularities. [One is to 1) Place the ingredients together in opposite order and 2) not mix the batter in a way that is usually done with a spoon or fork.] Some Poskim however rule it is permitted to make Tehina regularly on Shabbos, even if the mixture will not be thinner than usual. [Practically, one is not to make Tehina on Shabbos unless he follows the regulations mentioned above which are 1) Thinner batter than usual and 2) Place the ingredients together in opposite order and 3) Not mix the batter in a way that is usually done with a spoon or fork.]
Adding more water to a Techina dip: If water was mixed into the Tehina from before Shabbos and one now desires to make it thinner, it is allowed to be done so long as the Tehina will not thicken in the interim. Nevertheless, one may only mix the water using ones hands rather than a spoon, or use another form of irregularity.
Thickening it: If the Tehina is too liquidly, it remains forbidden [according to the main opinion above] to add any Tehina or other food to the mixture to make it thicker [unless the final batter will still be thinner than the way it is made during the week, and one uses the above two forms of irregularities].
 SSH”K [new edition]; Shabbos Kehalacha 22/60; Piskeiy Teshuvos 321/27-7 and footnote 270; And so is the ruling according to Tehila Ledavid 321/21 and Ketzos Hashulchan 130/3 footnote 8 in name of Igleiy Tal 30 that so is ruling according to Rebbe Yehuda, brought in Michaber 321/16; Implication of Biur Halacha 321 “Yachol Learbevo” which negates the explanation of P”M 321 M”Z 13 and implies that by Bar Gibul, even according to Rebbe Yossi there would be a prohibition in doing so; So rules also Chazon Ish 58/8-9; however see SSH”K 8/7 who allows adding other liquids to the food even if it was not mixed with external liquid before Shabbos; See Piskeiy Teshuvos 321/25
 The reason: This matter follows the same dispute as mentioned above [in Halacha 1]. According to the first opinion mentioned the mixture is already considered kneaded, and thus adding liquid is allowed. As according to the first opinion the prohibition of kneading is simply to join two items into one, which is accomplished even when kneading food with its own liquid. However according to the second opinion the mixture is not considered previously kneaded unless it was kneaded with a substance other than its own. As they hold that the main aspect of kneading is the adding of ingredients, and here no ingredients were added, as the food naturally came with it. Therefore according to them in the above cases remain forbidden to add water on Shabbos to the mixture. The final ruling: As was explained above we are stringent like both opinions, and thus this may not be done [unless made into a thin batter with an irregularity]. To note that if the food is Bar Gibul, then according to some Poskim this would be forbidden even according to Rebbe Yossi, as explained above from M”B.
 See above Q&A regarding the definition of a thin batter.
 Or Letziyon 2/33-7; Many Rabbanim including Yalkut Yosef; Rav Avraham Yosef; Rav Dov Lior; Tehila Ledavid 321/21 that so is ruling of first opinion in Michaber 321/15 as explained in P”M 321 M”Z 13 [brought in M”B 321/? and Biur Halacha ibid] that if the mustard was kneaded with its juice before Shabbos it may be kneaded even into a thick mixture on Shabbos with a Shinuiy.
The reason: As the Melacha of Lash is only when one connects pieces together and not when one dilutes a food.