# How long for medium rare 2 pound roast beef and evaporation?
**URL:** https://community.anovaculinary.com/t/how-long-for-medium-rare-2-pound-roast-beef-and-evaporation/352
**Category:** Anova Precision® Cooker
**Tags:** beef, timetemp, steak
**Created:** [February 18, 2015, 12:26pm UTC](https://community.anovaculinary.com/t/how-long-for-medium-rare-2-pound-roast-beef-and-evaporation/352 "2015-02-18T12:26:33Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Gary1976](https://community.anovaculinary.com/u/Gary1976)
#### Post date: [February 18, 2015, 12:26pm UTC](https://community.anovaculinary.com/t/how-long-for-medium-rare-2-pound-roast-beef-and-evaporation/352/1 "2015-02-18T12:26:33Z")
Hi, I would like to know how long I need to cook a 2-pound (1kg) tenderloin roast beef. I see from recipes 2-48 hours, but I would need a bit more precision… I am also concerned about evaporation while leaving the Anova on throughout the night…
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### Author:  [@jordan](https://community.anovaculinary.com/u/jordan)
#### Post date: [February 18, 2015, 5:43pm UTC](https://community.anovaculinary.com/t/how-long-for-medium-rare-2-pound-roast-beef-and-evaporation/352/2 "2015-02-18T17:43:51Z")
@Gary1976 You’ll want to insulate the vessel you’re cooking in to avoid losing too much water - some of our community members have come up with some great solutions in this thread: [http://community.anovaculinary.com/discussion/comment/1532/#Comment\_1532](http://community.anovaculinary.com/discussion/comment/1532/#Comment_1532)
The sous vide cooking method is much more about the precision of temp rather than time, which is why you’re seeing a lot of variance in the recipe cook times. What is the thickness of the tenderloin you’re cooking?
If you take a look at Kenji’s recipe on Serious Eats, you’ll see a little more background on the technique for sous vide tenderloin: [Sous Vide: Beef Tenderloin with Lemon-Parsley Butter Recipe](http://www.seriouseats.com/recipes/2010/08/sous-vide-beef-tenderloin-with-lemon-parsley-butter.html)
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### Author:  [@psiu\_glen](https://community.anovaculinary.com/u/psiu_glen)
#### Post date: [February 24, 2015, 1:51am UTC](https://community.anovaculinary.com/t/how-long-for-medium-rare-2-pound-roast-beef-and-evaporation/352/3 "2015-02-24T01:51:09Z")
I have found that if I am planning that long of a cook, I will place some saran wrap over the top to help hold in the evaporation. Also, the evaporation is slow enough that you can simply add a couple of cups of water and it will only drop a few degrees before coming back up to temp.
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### Author:  [@jordan](https://community.anovaculinary.com/u/jordan)
#### Post date: [February 24, 2015, 6:16pm UTC](https://community.anovaculinary.com/t/how-long-for-medium-rare-2-pound-roast-beef-and-evaporation/352/4 "2015-02-24T18:16:15Z")
@psiu_glen True, great point! Haven’t tried saran wrap yet but will give it a go for longer cooks. Thanks!