I had been hearing from a few other brewers recently about the speed at which they run their mills. Hearing about optimum speeds and not full speed or not too fast. I’m sure I had heard this before but probably not paid attention at the time as I was getting my grain pre-milled.
Now I’m milling my own grain on the brew day and having heard these discussions about milling speed finally decided to see what the fuss was about. I did do a bit of reading over at homebrewtalk.com (this thread) and it seems that there is much discussion (surprise, surprise) about rpms vs face roller speed. I also found this quote on http://www.theelectricbrewery.com/grain-mill:
Milling should be done at low RPM (revolutions per minute) to avoid shredding the husks. Somewhere around 150-250 RPM (around 2-4 turns/second) is said to be a good compromise between the time taken and the amount of shredded husk material. At this speed it takes us approximately 2-3 minutes to mill the 15-20 pounds of grain required for a typical 10 gallon batch of beer.
I have to admit, I just wasn’t aware of that. Likely because I spent a fair bit of brewing time not having a mill. Once I did get a mill I just attached my drill and let ‘er rip… or crush, or whatever is supposed to happen.
So hearing about these points I decided to try my own rather non-scientific test to see if there was a difference. I attached my drill and did a run at it’s highest speed and a run at the lowest speed I could maintain. I then photographed the results:
Crush at highest drill speed
Crush at slowest drill speed
I don’t really notice a difference.
Now, it may be that if I brewed a batch with a slow crush grist and a batch with a fast crush grist there might be difference in efficiency. It may also be something that is far more noticeable or applicable in larger scales like a commercial brewery would be dealing with. This may be like the many discussions that homebrewers have about hot side aeration.
I’ll leave it to you to assess the results and… Discuss.