My grinders have all changed every 20-25 pounds... with the seasons.

Pressino wrote:As far as the burrs themselves, grinding coffee can do only two things: 1) wear down the burrs, starting with their sharpest cutting edges; and 2) scouring the burr's flatter surfaces (not sure if they would be made smoother or a bit rougher...that's where SEM images of the burr grinding surfaces would be helpful).

According to Denis at Kafatek coating the burrs "sputters" the coating onto the metal. This leaves a somewhat bumpy surface. Seasoning is when those bumps get worn down. He has micrographs.

All coated burrs in theory.

I think that there are three different things being discussed here.

1. deburring, a.k.a. break-in. It wasn't that long ago that burrsets came from manufacturers fresh from the milling machine/grinder. These burrsets had burrs on the edges - folded over bits of metal from the machining/grinding/sharpening processes. Hard beans and/or something like minute rice got rid of these small burrs. Getting rid of these small burrs has to be done before coatings are applied, so we don't see this much anymore. (Coatings like Titanium Nitride, Red Speed, Silver Knight, etc.) Some form of bead-blasting is typically used to get rid of these small burrs before the coating is applied. Some burrset manufacturers used to be infamous for needing many, many pounds of coffee to get rid of these small burrs.

2. smoothening out coatings. This is most well-known with the Alpha coating used by Kafatek. Alpha is deposited on the burrs as (more-or-less) microscopic droplets, and these droplets need to be smoothed out, with many kg of coffee needed to do this. Whether other coatings need this, and how much - I don't know. There are many ways to apply coatings, and many coatings, and many are proprietary.

3. (actual) seasoning. This is no different than seasoning a cast iron frying pan. The traditional way was to get some dark-roasted coffee, and run it through the grinder continuously - but with a slow feed rate to not strain the motor. This would get the burrs stinkin' hot and deposit the coffee oils on the burrset, where the oils would polymerize from the heat and form a hard coating, just like oil does when seasoning a cast-iron frying pan. If the burrset doesn't get hot enough, then running coffee through does nothing except leave coffee oil on your burrs to go rancid. Typically 2kg or 3kg of dark roast is good for this.

As for electron photos and similar, all the machine tool coatings companies have them. There's no difference between tool steel in a burrset and tool steel in a drill bit.

There is this Gagné article the with some data:
https://coffeeadastra.com/2019/05/27/se ... quality-2/

Pressino wrote:OK, that's interesting. Does it apply to other burrs besides the Kafatek's. Micrographs, whether via SEM or just plain reflected light microscopy should definitely be illuminating (pun intended).

Interestingly, the Lagom Mini uses coating process to give different grind characteristics. The Obsidian burrs are given a rougher coating than the Moonshine which are polished.

baldheadracing wrote:3. (actual) seasoning. This is no different than seasoning a cast iron frying pan. The traditional way was to get some dark-roasted coffee, and run it through the grinder continuously - but with a slow feed rate to not strain the motor. This would get the burrs stinkin' hot and deposit the coffee oils on the burrset, where the oils would polymerize from the heat and form a hard coating, just like oil does when seasoning a cast-iron frying pan. If the burrset doesn't get hot enough, then running coffee through does nothing except leave coffee oil on your burrs to go rancid. Typically 2kg or 3kg of dark roast is good for this.

Now this I've never heard before. Isn't the smoke point of coffee oil up past 350 F? I can't imagine safely heating a grinder that much.

Not the grinder, the surface of the burrset. Burrs get pretty hot, maybe not 350F, but that doesn't matter. Polymerization of saturated fatty acids can start to happen at room temperature. Just under half of coffee oils are saturated. Heat speeds the process up.

This is a really interesting thread!

I just bought a new grinder! Got a good deal on an open box Ceado E37SD with the 83mm "opalglide" coated burrs. It was a static display model in a showroom; not one that someone used and returned.

When I bought my Rocky 14(?) years ago, I had never heard of seasoning burrs, so didn't do it. Now that I have this new grinder and am aware of the concept, I am looking for thoughts and opinions on what to do. I will only be using it for espresso.

Seems like people's opinions are divided on whether new burrs need seasoning or not.

This https://coffeeadastra.com/2019/05/27/se ... quality-2/ article posted earlier was interesting and went into a great deal of detail about surface area and whatnot, but never seemed to address how the coffee itself differed at each point in the process, leaving me with more questions than answers about whether seasoning really did anything terribly useful. Perhaps I missed the points made.

So, have opinions changed about seasoning? Is there a consensus? I do have some old beans kicking around I could run through it, but not a massive amount.

Thanks for your thoughts!