Not too long back I read some post, I think on here about grinding beans twice. I have some Colombian beans I roasted just to the end of the first crack and trying to get them to extract evenly each time in my espresso machine for Americano's was really difficult (actually almost impossible). You could see a lot of silver skin in the grounds so I decided to give that info about grinding twice a try. I'm here to tell you, it works fabulous. I ground 25 grams extremely course, like rock salt. Screened them and blew out 99% of the silver skin, and there was a lot. Then ground them again for my espresso machine. Knowing they were going to extract much better just from the looks, I went ahead and increased the grind size from .006" to 008: to start with for 18 grams of coffee. That gave 30 grams in 23 seconds and a world of difference in flavor. I've done five extractions using the same process and they have been almost dead on the same, so now I'm a firm believer in grinding twice for light roasted coffees or any roast you are getting silver skin in.

This process can harm your grinder, so I'd be careful with that.

The silver skin, or chaff, really isn't a big deal. Light roasted coffees usually have a lot more chaff intact, but flavor wise has very little impact on the coffee.

How could it possibly harm a grinder? Maybe if you threw pounds of pre-ground in a grinder and it managed to jam the burrs and you were stupid enough to let that burn out the motor, but single dosing?

Ira

It sounds interesting, but I'll never try it.

Some coffees don't work, or look great as espresso.. and I'm ok with that.

ira wrote:How could it possibly harm a grinder? Maybe if you threw pounds of pre-ground in a grinder and it managed to jam the burrs and you were stupid enough to let that burn out the motor, but single dosing?

Ira

The one reason I've heard that it creates significantly more fines and can clog much easier. Some grinders have less sealing from the hopper to the burrs where the coffee grounds can get in.

All I know is that every grinder I've ever used or bought has explicitly said not to regrind coffee, both in home and commercial settings.

41fivestar wrote:All I know is that every grinder I've ever used or bought has explicitly said not to regrind coffee, both in home and commercial settings.

And my car says don't drive with traction control disabled, but so what.

We're, and I hope I'm not abusing that word, not doing this to grind a pound of Yuban for espresso, which is what the grinder vendors are talking about. Nor are we the customer at Trader Joe's who just realized they ground their coffee for press pot when they really wanted drip, it's being done by people experimenting with ways to get better quality espresso and very carefully grinding 20 grams of coffee at a time.

Ira

The first grind is not really a grind, it's basically just broken up into chunks. Those 83mm burrs spit that second grind out so fast, the first time I didn't think it ground all of it. I don't think it takes more than a couple seconds. I have a hard time seeing how it could damage the grinder. As for clogging it up, there really are not places in mine to clog and it's not hanging in the burrs, I screwed the top off and checked that.

My taste buds are fairly dumb when it comes to knowing much about the taste of coffee, but even my dumbest ones can still taste the difference taking that silver skin out makes.

Plus, it's nice getting consistent, even extractions when I take it out, that was not possible before I did.

Why not just use a cheap blade grinder then. I thought the whole idea with a good grinder was to have the burrs crush the beans into even size particles and avoid the fines, without heating (with the blade grinder) the already roasted beans.

Double Grinding
This has been discussed before by endles cycles and the Prufrock team ( linked in link above )
I'm not sure what grinder you are doing this with ( and hence if it had an auger / pre breaker )
It could be argued you are performing the function of this grinding twice but to a more consistent level ?

Which grinder are you using for double grinding?