headshaker wrote:I'm used to beer mashing,so why can't boil a whisky mash and sparge and separate in in my mash tun?
As noted by others, often whiskey ferments are "on the grain" because higher brewing efficiency maximizes the product, especially commercial distillers. Because the fermented "distiller's beer" will be distilled when fermentation is complete, the alcohol will be separated from the rest of the ferment "sludge". Sterilization of the wort is not near as critical when the product will be distilled.
But the brewing processes are similar, that is...you use the temperature of the sweet liquor and the active enzymes to convert starches to fermentable sugars. As a result, the target temperatures are different than your beer brewing rest temperatures. When the goal is fully fermentable conversion, you mash at the range optimum for fermentable sugars, that is, in the 145-148*F range. In addition, often times enzyme activity is supplemented with liquid gluco-amylase enzymes to "supercharge" the starch conversion.
But your question regarding the mash and sparging prior to fermentation...I lauter my all grain ferments as well.
Working with ground corn, especially when it is 50%+ of the grain bill, is difficult because the corn tends to plug the runoff drain grid in the lauter tun. But it can be done. I recirculate the wort in the tun to help establish a filter bed and I use barley malt with its husks to help the process. Rice hulls could also be added to help facilitate lautering.
Still, it is a challenge to get a good runoff flow. But it does make things easier once fermentation is done...I don't have to "squeeze" the spent grains to help extract the prized liquor out of the fermenter. A rack siphon is all it takes.
Many here prefer to ferment "on the grain" because it improves brewhouse efficiency, especially when using liquid enzymes. And fermenting "on the grain" also gives much more grain flavor to the distiller's beer when moved into the boiler. The disadvantage is the work involved with the transfer process. Messy.
So, your mileage may vary (YMMV) depending on what you're trying to accomplish. As I said, I lauter. It makes the process easier from the fermenter and on.
And there is no need to boil the wort in the kettle between sparging and fermenting either...enzyme activity, remember? But you should use the processes you're familiar with (and have the equipment with) to make the distiller's beer as you will. It is easy to formulate a recipe to account for a brewhouse efficiency according to your processes.
But keep in mind that corn can be a struggle to work with, especially when using a higher percentage of the grainbill. And also, I hope you know what rye does in a lauter tun....it's a sticky, gooey mess.
ss