Different kinds of malt and lactose are staged and ready to be added to the brewing process.
Boiling hot water, oats, barley, salt and other ingredients are added to the masher at the beginning of the brewing process.
The "mashing in" or mash process is where the ingredients like the milled grain are mixed with hot water, which is approximately 158° F (Fahrenheit) or 70° C (Celsius). Mashing is the brewer's term for the hot water steeping process which hydrates the barley, activates the malt enzymes, and converts the grain starches into fermentable sugars. Brewers monitor the mash temperatures very closely.