2) The water of Netilas Yadayim must wash the entire hand. Therefore, before washing it is best to examine the hands to ensure that there isn’t any [significant]dirt that may cause the water not to cover that part of the hand, and thus be a Chatzitzah- separation (Mishna Berura Siman 161:1) If the item stuck to the hand is small and insignificant, and most people wouldn’t bother to remove such dirt, even if it bothers you personally, it isn’t a Chatzitza. imilarly, if the item is of the nature that most people would remove it, even if it doesn’t bother you personally, it is a Chatzitza and must be removed. (This is only the general rule, there are certain exceptions, which we will see shortly) 

3) One whose “hands on” profession leads to his/her hands regularly being stained (e.g. construction workers, butchers, painters, artists, Scribes etc.) may wash Netilas Yadayim on the soiled hands, if the cement, grime, ink etc. isn’t covering most of the hand, and it isn’t something that he/she usually bothers to remove while working. This is true, even if most other people would be bothered by similar grime, and would run to clean it off. (Shulchan Aruch Siman 161:2 and Mishna Berura S”K 11. See also Shu”t Teshuvos V’hanhagos Vol. 2 Siman117)

4) A Chatitzah (separation) only prevents proper washing if it is a tangible stain on top of the hand, such as dried ink, paint, cement etc. Simply having a small pen mark or similar stain which cannot be lifted off the hand, is not a problem and the hand may be washed. Similarly, wet ink or paint, which will move around as you wash your לע"נ היקר באדם ר' אברהם אלעזר בן דוד ז"ל והאשה החשובה מרים ריזל בת ר' משה דוב ע"ה hands, is not a Chatzitza, as the water is able to reach every part of the hand.(See Mishna Berura 161:14. See also Igros Moshe Orach Chaim Vol. 2 Siman 110) A wound that is healing and develops a scab is not a Chatzitza unless it bothers you and you regularly remove it. (Mishna Berura 161:16) Noticeable dirt on the fingernails, under the fingernails, or part of a fingernail that is loose and hanging is a Chatitzah and must be removed before washing Netilas Yadayim. If the dirt is insignificant, and not bothersome enough that people usually remove it, it isn’t a Chatitza. (See Shulchan Aruch HaRav 161:4 and Kaf HaChaim 161:4)

 5) Women (and men who wear rings) must remove their rings before washing, as the rings are usually removed when a woman kneads dough or otherwise handles messy things. However, if the hands were washed with the rings on, if the rings are loose fitting she doesn’t need to wash again, as B’dieved it isn’t a Chatzitza. (Mishna Berura 161:18. See also Shu”t Rivevos Ephraim Vol. 1 Siman 127 regarding a woman who never removes the ring at all even for kneading dough. See also Kaf HaChaim 161:32) Many women “hold” their rings between their teeth while washing and making a Bracha. This practice is not commendable as the mouth must be empty when saying Brachos. The best thing is to remove the rings and place them down on the counter or table before washing. 

6) Women who wear nail polish may wash on top of the nail polish, since they want the polish there, it is considered part of the hand and isn’t a Chatzitza (This Halacha is for hand washing only, and should not be applied for a woman going to the Mikvah, as in that case she needs to remove the nail polish). However, if the polish is cracking and brittle and she plans to remove it, she must do so before being able to wash Netilas Yadayim. Men may not wash on top of nail polish, even if they want it there, as it isn’t the norm for men to wear nail polish. One who has a band-aid on his/her hand must remove it for washing, lest it fall off during the meal. However, if by removing the band-aid it will cause pain or puss to develop, it is not a Chatzitza and may be left on. If the band-aid falls off or is removed during the meal, the hands must be rewashed before continuing to eat. (Mishna Berura Siman 162:71. See also Sha’ar HaTzion Os 58 where he debates whether the entire hand must be rewashed or just the place where the bandage was)