Thin and Thick Masses – Blila Raka and Blila Ava
- We mentioned that one of the criteria for the melacha of lisha to apply is that the substances must combine together to form a single mass. There are two distinct types of masses discussed in halacha, each of which has a different status when it comes to the leniencies we are about to discuss.
- Blila ava’ – a thick mass. This is a mass that cannot be poured from one utensil to another; for example tuna mixed with mayonnaise.
- ‘Blila raka’ – a thin mass. This is a more liquidy mass that can be poured from one utensil to another, for example a thin baby porridge.
- The Torah level prohibition of lisha applies only to making thick masses, whilst on a Rabbinic level one may not form thin masses in the normal way either. (SSK 8:8-9)
Making a Thin Mass – Blila Raka – with 2 Shinuyim
- Given its more lenient status, one is permitted to make a thin mass, if one employs two ‘shinuyim’, two changes from the normal manner of kneading a mixture, as follows:
- Shinuy 1: Reversing the normal order of adding the ingredients.
- For example, if on weekdays one would typically put the liquid substance in first and then add the dry substance, on Shabbos one should put the dry substance in first, and vice versa.
- Where one does not have a ‘normal’ order in adding the ingredients, one should add the dry substance first and pour the liquid substance in thereafter.
- Where the dry substance is being added first, one should ensure to subsequently pour in all the liquid in one go, without pause, to ensure that it immediately forms a thin mass, rather than pouring the liquid in slowly such that it initially forms a thick mass which is then thinned out.
- Shinuy 2: mixing the substances together in an atypical manner, for example with one’s finger, or by rocking the utensil they are in.
- Where one needs the help of a utensil such as a spoon, one should stir the mixture in a ‘criss-crossing’ fashion (eg making one stroke from north to south, followed by one east to west etc), ideally taking the utensil out of the mixture between each stroke. (SSK 8:9)
Making a Blila Ava – Thick Mass
- Ideally one should entirely refrain from making thick masses on Shabbos given their more stringent status.
- Where one is unable to make a thick mass prior to Shabbos as it will ruin by the time one needs it on Shabbos:
- Where possible, before Shabbos one should add enough of the liquid to the solid to saturate all the solid and stir it a little. Thereafter, one may add further liquid to the mass on Shabbos, ensuring to follow the two shinuyim outlined above.
- If even this small preparation is not possible before Shabbos, as the substance needs to be fresh eg for a baby, or if one forgot to do this preparation and is in need of the food on Shabbos, one may rely on the lenient views in the poskim who permit one to make a thick mixture on Shabbos, so long as one employs the two shinuyim above (of reversing the order of adding the ingredients and mixing them in an unusual fashion). For example, where needed for a young child, one may crumble a biscuit and mix it with cream cheese, using the two shinuyim (SSK 8:10-11, 18).
Exceptions to the Rules of Blila Raka and Blila Ava
- Fully liquid mixtures: Where the mixing of two substances together creates an entirely liquid mixture, this is not considered a ‘mass’ that is problematic under the laws of lisha and this may be done as usual on Shabbos.
- For example, there is no concern of lisha when making coffee, hot chocolate or baby formula (though one must be mindful of the halachos of bishul – cooking: cooked powders may be added to hot water in a kli sheni, uncooked powders may only be added into water in a kil shlishi) (SSK 8:13, 23, 29).
- When substances combine without mixing: where the very act of combining substances causes them to stick together into a mass, without need for stirring, these substances may not be combined even by employing the shinuyim outlined above (as a ‘shinuy’ made at the stage of mixing is already ‘too late’ to save one from the melacha).
- Therefore, one may not make use of powders that form into food when adding water, for example jelly, pudding or mashed potato powder. (SSK 8:29)
Thickening and Thinning Existing Mixtures
- Thinning out an existing mass: where different substances have previously been mixed together to form a single mass, it is permitted to add a liquid to this mass in order to thin it out on Shabbos, as this is in effect the opposite of the melacha of Lisha – lash is defined as causing items to combine together, whereas this is similar to separating them out.
- Nonetheless, this must be done with a mild ‘shinuy’, by stirring in a gentle rather than forceful manner, so that it does not look similar to lisha (SSK 8:7, BHL 321:15 DH Yachol).
- Thickening an existing mixture: by contrast, one may not thicken an existing mass, such as by adding more flour to an existing dough. (SSK 8:12)
