In the days before modern highly-modified malt, it was often necessary to take extra steps in order for the starches to be adequately converted into well-conditioned wort. With today's malt, step-mashing is not a requirement, and can sometimes result in converting too many sugars to fermentable form, which it turn can result in very low finishing gravities, and thus, dried-out and thin-tasting beers. However, for certain styles, it is useful, and can result in excellent mash efficiency.
Step-mashing involves bringing the mash temperature up to a certain level, resting there for a period of time, increasing again, etc. In the hot water infusion method, the mash starts off with a low water/grain ratio. When the heat is required to be increased, hot water is added in amounts and temperatures calculated to result in a specific overall mash temp and water/grain ratio. A typical stepped mash can include several steps:
- Add initial hot water to achieve initial mash temp of 133f
- Hold 133f for 30 minutes [Then add hot water to increase overall mash temp to 149-155f]
- Hold 149-155f for 45 minutes [Then add hot water to increase overall mash temp to 158f]
- Hold 158f for 10-20 minutes, or until an iodine test indicates starch conversion is complete
- Add hot water to increase overall mash temp to 167f
- Sparge with 170f water
