Question: How particular should one be to wear a silk kapoteh, and is there any times where silk is not necessary? What is our view on wearing a kapoteh which is partially silk, since silk can be quite costly.

Answer: One should wear a silk Kapota on Shabbos and Yom-Tov. A blend of wool and silk wouldn’t be considered a silk Kapota unless it’s made with a majority of silk (which to the best of my knowledge is usually not the case with most blended Kapotas available).

It should be noted that as a general rule the the money one spends on Shabbos and Yom-Tov clothing isn’t included in the amount of money one is destined to make throughout the year.

For the source of the custom see here.

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