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Procedure of Urchatz
- One should wash one’s hands without a bracha before eating the Karpas. 
- This washing should be like washing for bread in all ways except that we don't say the beracha. 
- One should wash even if he uses a fork and doesn't touch the food with his hands. 
- The Karpas should be dipped in a vinegar or salt water, and then make a HaAdama on the Karpas. 
- One should eat less than a keziyat of Karpas so one won’t have to make a Bracha Achrona. 
- If one by accident made a Bracha on this washing one shouldn't be careful about keeping one's hands clean and obligate oneself in Netilat Yayadim for Rachsa. 
- One shouldn't talk between the washing and the eating for karpas.  It is for this reason that many recite the simanim "Urchatz Karpas" before washing his hands, since he should not speak after washing his hands. 
- It is proper to have in mind that one's washing for Urchatz doesn't exempt one from washing later for the meal. It is preferable to cause oneself to be obligated to have to wash for the meal before Rachsa.
- S”A 473:6. This is based on the gemara Pesachim 115a which states that before whatever is dipped in one of the seven liquids (wine, honey, oil, milk, dew, blood, water) requires washing your hands before eating it.
- According to most rishonim this is a legitimate rabbinic decree like washing for bread. This is quoted in the Rambam Berachot 6:1-2, Tur 473 quoting Rashi and the Geonim, Rosh Chullin 8:10. Peri Megadim Mishbetzot Zahav 158:4 and the Chazon Ish 125:4 quote Tosafot Pesachim 115a "shetibullo bikmashke" that this washing is only precautionary to prevent someone from violating the rabbinic prohibition of eating impure foods and therefore no beracha is recited. Therefore, the Tur 473 quotes the Maharam MiRotenberg who says that this doesn't apply today because there is no longer even a rabbinic prohibition to eat impure foods.
- Shulchan Aruch 158:4 and 473:6 rules that since it is a machloket rishonim one should wash without a beracha. The Gra 158:4 rules that one should wash and say a beracha but the Mishna Brurah 473:52 says even the Gra only says this when one eats a Kezayit or more. Magen Avraham 158:8 quotes the lechem chamudot in chullin perek kol habasar 41 that the custom is not to wash for moist foods and if you don't you have who to rely on. Aruch Hashulchan 158:4 wrote that we are lenient with this washing.
- Mishna Brurah 158:20, Ben Ish Chai Tazria halacha 16, and Kaf Hachayim 158:25 say that even though we don't say a beracha, one should be stringent in washing for this because most rishonim and achronim said that one must wash. The Ben Ish Chai Tazria Halacha 17 says to be machmir for even less than a Kezayit and his proof is that we eat less than a Kezayit of karpas and still wash for it. Mishna Brurah 158:20 says though that if it is less than a Kezayit there is no need to be stringent at all.
- Even those who aren't careful during the year usually wash on seder night. The Shaar Hatziyun 473:6 quotes the Chok Yaakov writes that the reason for this is to get the children to ask questions. The Taz 473:6 says there is no reason for this and that it should show people that they should be stringent during the whole year and not just seder night. The Levush 473:6 justifies the custom by saying that we act with greater purity out of our loves for the holiday and the obligation to dip. Rav Mordechai Breuer in Pirkei Moadot volume 1 page 180 quotes the netziv as explaining that on the seder night we attempt to imitate the pesach seder from the times of the beit hamikdash where according to everyone they would wash.
- Kaf Hachayim 473:106, Chazon Ovadia Pesach page 136, Mishna Brurah 158:20 quoting the pri megadim.
- Even though Mishna Brurah 158:14 is lenient in this case for during the year, Rav Tzvi Pesach Frank in Mikraei Kodesh 2:39 says to be machmir on seder night to arouse the children's curiosity. Nitei Gavriel (Pesach v. 2, p. 403)
- S”A 473:6
- S”A 473:6. The Maharil 25 quotes an argument between the Ri who says you would say a beracha acharona and the Rashbam says you wouldn't so we eat less than a Kezayit to avoid this problem. Rav Moshe Harari in his sefer mikraei kodesh page 206 footnote 4 says that is the yemenite custom to follow the Rambam Hilchot Chametz umatza 18:2 and eat more than a kezayit.
- Chazon Ovadyah (pg 64), Rivevot Efrayim 1:301, Beiur Halacha 475:1, Halichot Shlomo Pesach 9:26.
- Chazon Ovadia Pesach page 32.
- Seder Haaruch pg. 313
- Nitei Gavriel (Pesach v. 2, p. 403). See Pri Megadim M"Z 473:1