We have these new baby bottles that have an indicator color strip to let you know if the liquid is too hot or too cold. This is something that is nice to have but we don’t really look at it much. Can I use such a bottle
Lechatchila on Shabbos?
A similar situation is with diapers that have a wetness indicator strip, but that color change is forever, meanwhile in these bottles the color goes back to its original status eventually.
Can this case, therefore be compared to photo chromatic lenses that Rav Moshe was Matir?
Thank you for looking at this question. Would you please provide some sources in your answer?
Such a bottle should not be used on shabbos according to most poskim. This is because when the hot water is placed inside the bottle it causes the color to change temporarily, which is tzoviah d’rabonon. This is similar to using a heat sensitive thermometer, which most poskim do not permit on shabbos. This is different that the wetness indicator strip on a diaper, because of a number of factors. The color of the diaper is not being changed by the adult, but only by the child, therefore the issue over there is not to give something forbidden to a child (called safinan b’yodayim). However there are instances when it is permitted such as in this instance because putting the diaper on the child will only cause the child to riun the color in a grama (causative and delayed) fashion, which is only d’rabonon, and it is also a psik riesha d’lo ispas lei, the child is not really benefiting from the actual change in color the child except for the fact that his parent knows that he has to be changed. Together with the fact that it is for the good of the child, and safinon b’yodayim would be permitted if the issur is only a d’rabonon for his benefit. Because of all these factors the color strip on the diaper is permitted.
Chut Shani Shabbos 1 pg. 147, Machazeh Eliyahu 1 -66,67, NIshmas Shabbos siman 328-339, Avnei Yoshpe 2- 38, Shmiras Shabbos Khilchoso 15-88 ftnt. 275 in the name of R’ S. Z. Auerach zt”l, M’bais Halevi 19 pg. 50, Chut Shani Shabbos 4 pg. 287.