As we have seen, the Torah prohibition of Lash applies to forming a thick mixture. This means that many discrete particles become one solid mass that will not flow or spread out if left on a plate or bowl. In contrast, it is not forbidden by Torah law to form a loose mixture that can be poured from utensil to utensil and that spreads outward if left on a plate or bowl. This is because making such a mixture does not involve kneading, but only stirring. However, since one might mistakenly assume that if one may make a loose batter he may also make a thick dough, the Sages created a fence around the Torah and forbade forming a loose mixture. But one may make such a mixture with a shinui that serves as a reminder that there is a prohibition involved, ensuring that no one will end up making a thick mixture.
The shinui may be in the order the ingredients are added to the mixing bowl. If normally the dry ingredients are added first, followed by the wet ingredients, the wet ingredients should be added first, followed by the dry ingredients. If normally the wet ingredients would be added first followed by the dry ingredients, that order should be reversed. When following this procedure, one must make sure to add the liquid all at once so that a thick mixture will not be formed in the process of making a loose one.
Some maintain that it is unnecessary to incorporate an additional shinui during the stirring stage, as long as the mixture is not stirred as vigorously as one does during the week. Others are more stringent and require a shinui during the stirring as well. For example, instead of stirring the batter using a circular motion, one may stir in straight lines, from side to side, or perpendicularly. Alternatively, one might mix the batter with one’s finger, by shaking the bowl, or by pouring the batter from bowl to bowl. Le-khatĥila it is proper to comply with all the poskim and change both the order the ingredients are added and the way the batter is stirred.
When the ingredients are not usually added in any particular order, the dry ingredients should be added first, followed by the wet ingredients. Additionally, the way the mixing is done should be changed.
One may add liquid to a thick mixture to make it thinner, since this is the opposite of kneading. Kneading leads to discrete units coalescing, while adding water weakens the cohesiveness of the component parts (BHL 321:15, s.v. “yakhol”).
According to this, water may be added to raw tahini, since that makes it more liquid. However, some prohibit doing so, since during the process there is a stage in which the mixture becomes a bit harder (SSK 8:31). Nevertheless, halakha in practice follows those who are lenient, since the eventual result is a loose mixture. Additionally, since the sesame seeds in the tahini were ground and mixed before Shabbat, according to many the prohibition of Lash no longer applies (SA 321:15). In order to avoid any doubt, it is proper to mix with a shinui.
. According to Derisha, a number of Rishonim maintain that changing the order of the ingredients is sufficient. However, Terumat Ha-deshen §53 maintains that one must also change the manner of stirring. SA 321:14 rules that one need not change the manner of stirring (Menuĥat Ahava 2:9:43; Ĥazon Ish 58:5 s.v. “u-mashma” seems inclined to rule this way as well). However, according to MB 321:57 and Ben Ish Ĥai, Year 2, Mishpatim 18, it is preferable to change the manner of stirring as well as the order of the ingredients.When the ingredients are not usually added in any set order, one should begin with the dry ingredients, according to Terumat Ha-deshen, Eliya Rabba, Tosefet Shabbat, and Ĥok Yaakov. However, according to Taz, since in such a case it is impossible to change the order of the ingredients, making such a mixture is simply prohibited. This disagreement is cited by MB 321:57. Since this is a rabbinic law, one may rely on those who are lenient (SSK 8:9; Menuĥat Ahava 2:9:39).