choosing mash temperature

I'm thinking of doing a partial mash this weekend and I'm trying to decide what temperature to use. This will be my third partial mash. It will be a stove top mash.

How do I choose the temperature? I want it to be on the malty side, but with enough fermentable sugars to get a decent ABV. Are there any guidelines for mash temperatures by style? Is there any way to calculate the percent of fermentable sugar to unfermentable based on mash temp?

Or is there some way to calculate FG based on mash temperature and efficiency?

what percentage of your fermentables are you getting from the partial mash as opposed to the extract? if its less than say 50%, i'd just shoot for 150-152 degres, mid range, as it won't matter that much. if more than 50% you can think more about it.
what style of beer is it and what extract are you using (pilsner, extra light, dark, etc.)?

Whew, that's a big question with a lot of factors that influence it. What's your grainbill? What style of beer are you doing? What yeast?

All the above factors help determine what temperature to mash at. However, generally you want to stay between 148 and 158. For example if you're using a high attenuating yeast you'll want to mash a little higher than normal, say 154, to leave some maltiness. If you're using a lot of crystal however, you may want to go a little lower. Unfortunately there really isn't a calculator or straight chart that tells you what temp to mash at, you just have to do some research on how the above factors influence your beer and make a decision.

I haven't finish my recipe yet, but here's what I'm thinking. I want to do a wheat beer with citrus flavors that contrast some richer malty flavors. I'm thinking Cascade for the hops, plus some orange peel. So I'm thinking of something like a Blue Moon but richer and more malty.

Another question. Would I gain anything by steeping the crystal malt separately from the mash. I'm thinking that crystal malt would have some unfermentable sugars that might get broken down by the mashing, but would be left in tact if steeped separately.

I agree with Telemark - I've done dozens of partial mashes with 4-5 lbs of grain (about 40 total) and experimented with mash temps from 148 to 154. It doesn't make a huge difference, the largest difference I've seen with the same recipe was a couple FG points. I make a lot of pales and prefer the slightly drier finish in those so I'll mash at 150, for a maltier style I might do 152-154. At least it makes me feel like I'm trying, even if it doesn't really matter much in the end. Of course it will make more of a difference if your partial mash is 60-70% of your recipe.

Not sure about separately steeping the Crystal, I've always thrown it into the mash.

By chagning temps you'll get more variation in mouthfeel than you will in fermentability. A beer that feels twice as thick in the mouth won't be half as fermentable.

That said, the temp you aim for depends on so many factors, and 154F on your system might be different from others. So the best advice I think you can get is to aim in between 148 and 158 and you'll have a good beer.

If you want it really light go 148, and if you want the fullest body go 158.

If you're still trying to dial it in, I'd aim for 153F. That's smack dab in the middle of the commonly acceptable range. So next time you can go up or down if you feel you need to tinker with it.

But don't be afraid that you'll end up with a 'bad' ABV, because I don't believe you will.

Cheers!