Q. Due to the fear of the current contamination fears, many people who have guest for Shabbat avoid touching the challot with their hands when lifting them and cutting them for all. Since one has to place his two hands and the ten fingers on them and also lift them, can one do so using a thin paper napkin or is that a chatzitza (interposition)? What then should one do?
A. On some cases such as Tefilin or Bigdei Kehuna (clothing that Cohanim wear when they perform their service at the Beis Hamikdosh), water between them and the human body may be considered a chatzitza or interposition, since they actually may be required to touch the body. (Birkei Yosef O.H. 27: 8, Shaarei Teshuva O.H. 27: 5).
See also Chelkas Yaakov Y.D. 110, regarding a new born bechor that was delivered by using forceps if he is considered to be a Bechor.
Some Chassidic Rebbes have a tradition of lifting the challos by putting their hands under the tray holding them and since it is needed to hold them (some times there may be twelve challos) they are not considered a chatzitza.
See similar in regard to the utensils used for sprinkling the blood of the korbanos on Yom Kippur (Yuma 58a).
Horav Shlomo Miller’s Shlit’a opinion is that if the napkin is needed, it is not considered an interposition.
Rabbi A, Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a