Mashout madness

So, the true benefit of mashing out eludes me. I understand that the increased temp. halts all conversion while you sparge. But some folks mash for more than an hour, so what's the harm in a little conversion still occuring during the rinsing of the grain bed? Am I missing something abvious?

I always wondered the same thing. I have always batch sparged and just did my second run at the same temp as the first because I didn't want to get too hot and create tannin bitterness in my beer. I too, woul like to know what's up.

P.S. My beer has turned out pretty well even without the mashout.

Two benefit that I'm aware off are that it raises the temperature of the mash up to sparge temperatures, and decreases the viscosity of the mash. This is very useful when fly sparging, when the sparge water is added very slowly as the wort is being drained. In this case, without a mash out, the sparge temperature will probably not get above 160.
When I started doing a mash out (with a fly sparge), my efficiency increased from 75% to 85%.
On the rare occasions that I batch sparge, I also do a mash out. I know that adding 1g near boiling water is going to raise the temperature from mash temps to 168 - 170 so that each addition of sparge water can be at the same temperature. If I didn't mash out, I would have to calculate a different temperature for the first addition of sparge water.

-a.

I could see where thinning the mash out before fly sparging might help, but it doesn't seem that it would matter with a batch sparge.

What I really want to know, is why do you need to halt conversion? What are the benefits? Does anyone know.

Sea said:

What I really want to know, is why do you need to halt conversion? What are the benefits? Does anyone know.

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Keeping a beer true to style, you might need to mash out to stop all conversion so you don't go over the target OG.

that's all I can think of.

Increasing the temps increases the solubility of the sugar. For most people this just means a 1-5% increase in efficiency, but like ajf stated, it can be higher.