Originally Posted by ChessRockwell
With only crystal malts there's really not much need to even do a partial mash, you get everything you need from them by just steeping. With that said, I'd probably mash lower, like 152. You'll get enough unfermentables from the crystal and whatever extract you're using.
Mashing Crystal will get you more fermentables. Crystal does have starch that needs mashing to make it fermentable. If you steep Crystal, you might get 18 points/lb, but with mashing, you can get 30 points/lb with good efficiency.
Mashing crystal at lower temperatures makes it more fermentable than steeping too.
Don't dismiss the advantages of mashing crystal. However, it does not have any enzymes, so needs to be mashed with some base grains.
Originally Posted by Stauffbier
If you're looking for heavy body, then 155 will work. If you want it to be a bit more dry then lower that to 148-150. 45 minutes will likely be enough time for conversion, but you should really keep mashing until you get a good iodine test. Put some of the wort from the mash in a bowl and drop a few drops of iodine tincture in. If the iodine doesn't change color, then the sugar has been converted. If the iodine turns black/dark purple then let it mash longer.
I used iodine for my first mash. Never used it since then; too much hassle. If you get the temperatures correct, you will get conversion. 30 minutes is all that is needed.