May one blow bubbles on Shabbos?
Blowing bubbles on Shabbos enters into the question of whether it transgresses the Molid prohibition due to it changing the form of the water into foam. Practically, the mainstream approach follows that it does not contain a Molid prohibition, and therefore children may blow bubbles on Shabbos. However, it is best for adults to abstain from doing so. Furthermore, some Poskim rule that even children who have reached the age of Chinuch are to avoid blowing bubbles on Shabbos.
 See SSH”K 16:30; Shabbos Kehalacha Vol. 3 17:79; Piskeiy Teshuvos 326:13 footnote 161
 Evident from Ketzos Hashulchan 146:32; SSH”K ibid in name of Rav SH”Z Aurbauch; Shabbos Kehalacha ibid; Piskeiy Teshuvos ibid although writes that initially one should not instruct children to do so and it is just that if they do so they do not have to be protested
The reason: Although it is forbidden on Shabbos to change the form of an item, such as to turn ice into water, due to the Molid/Nolad prohibition, nevertheless the Poskim rule that the formation of foam/bubbles that becomes created when using soap to wash hands/dishes does not fall under this prohibition as the foam has no real substance, and does not last at all. [So rules Ketzos Hashulchan 146 footnote 32; Tzitz Eliezer 6:34; -14; in length; Beir Moshe 8:247; SSH”K ibid in name of Rav SZ”A; Piskeiy Teshuvos ibid; However some are stringent in this: See Ginas Veradim [Halevi] O.C. Klall 3:14 regarding hard soap; Shevisas Hashabbos Dash 61; Az Nidbaru 10:16] For this reason, also the placing of toothpaste on one’s teeth [without a tooth brush] does not consist of a Nolad prohibition, even though it creates foam in the process, as the foam has no substance. [Ketzos Hashulchan 138 footnote 31]. Accordingly, it would be permitted here as well to blow bubbles, being that the bubbles hold no substance and do not last. However, Tzaruch Iyun, as in the case of blowing bubbles one has intent to create the foam and it is thus unlike the case discussed above in the Poskim regarding soap bubbles, in which case one has no intent for them to be made. [see Shabbos Kehalacha ibid; Piskeiy Teshuvos ibid] Nevertheless, it is clear that the Ketzos Hashulchan 146 footnote 32 learns it is permitted even a case that one intends to make the bubbles, as he also explains that it is permitted to make seltzer for this reason, even though one certainly has intent to create the bubbles.
 SSH”K ibid; Shabbos Kehalacha ibid
The reason: As one intends to make the bubble and it is hence unlike the case discussed regarding soap bubbles in which case one has no intent for them to be made. [SSH”K ibid; Piskeiy Teshuvos ibid]
 Shraga Hameir 7:44; Koveitz Mibeiys Halevy 6:44 in name of Rav Shmuel Wozner and Nishmas Shabbos 250, brought in Shabbos Kehalacha ibid footnote 192
 The reason: As nevertheless, one has intent to make the bubbles and it is hence similar to Molid Davar Chadash. [ibid]