# Passover questions (flour)
**URL:** https://boards.straightdope.com/t/passover-questions-flour/100611
**Category:** Factual Questions
**Created:** [March 28, 2002, 7:30pm UTC](https://boards.straightdope.com/t/passover-questions-flour/100611 "2002-03-28T19:30:04Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Moe](https://boards.straightdope.com/u/Moe)
#### Post date: [March 28, 2002, 7:30pm UTC](https://boards.straightdope.com/t/passover-questions-flour/100611/1 "2002-03-28T19:30:04Z")
Why is flour not kosher for passover? I understand that way back when, the Jews were unable to let the bread rise, thus forcing them to eat unleavened bread, but: -I thought that yeast was responsible for bread rising and -Matzah contains flour (though this flour is apparently differentiated as _simple_ flour). What if something contained flour but was still to remain unleavened, would that be considered unkosher?
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### Author:  [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)
#### Post date: [March 28, 2002, 7:38pm UTC](https://boards.straightdope.com/t/passover-questions-flour/100611/2 "2002-03-28T19:38:15Z")
From [this site](http://www.ou.org/chagim/pesach/pesachguide/maze/basic8.htm):
> [@](#):
>
> **Chametz**
> Fermented or leavened wheat, rye, oats, spelt and barley. When these grains come in contact with water, they leaven within 18 minutes. In the case of hot or salted water, leavening takes place instantly.
>
> Chametz may not be consumed either by eating or drinking, and may not be held in one’s possession, nor may any benefit be derived from Chametz. Grain flour is commonly produced from grains that have been washed and tempered. Tempering is the process by which grains are softened by soaking in water, and this flour and all products made with it are, therefore, chametz.
Hope this helps.