I have learned a little about coffee and most of it theory and most of that from the internet. I finally had a situation where theory became reality. Internet factoids became coffee master wisdom.
We may have a dual compartment commercial Bunn grinder tucked away in my friend's office; but if the Office Police come through, I will plead the 5th. The grind is so much more consistent and about 500% faster than the hand grinder. Its worth risking because the coffee is much better.
The dual compartment is nice because it allows us to roast a couple different kinds of coffee and have a selection to chose from. Variety is the spice of life, ya know. Having 2 different types of coffee right next to each helped me see how different the weights of coffee beans are.
This grinder (I believe it is a G9) has what I'm going to call a "timed drop plate." The beans are held up by a little plate at the bottom of the hopper. When you start the grinder it will drop the plate for a set period of time and then close. We had set the time on the Colombian coffee from a while ago. It would grind 29g (plus or minus 1-2g) pretty consistently. It was working swimmingly, except for the few noise complaints that we quickly disregarded as nonsense from those who do not truly understand.
Then we ran out of coffee. It was rough week with lots of blank stares followed by longing gazes. We both committed to roasting coffee over the weekend, taking us from famine to feast. I had roasted more Colombian and my buddy had roasted some Chiapas.
Normally we just brew two batches of the same coffee, but for some reason my friend wanted to be difficult. He asked for Chiapas, but I was sticking to the Colombian. I ground my Colombian and poured the grounds in the V60, checked the weight. 27g. Not bad. I adjust the water by 32g and I'm right as rain. I brew my cup and enjoy the pleasant floral aroma. I give my friend a disapproving look and switch the grinder to the Chiapas. Grind and dump it in the V60. It's 40g.
I didn't understand. The grinder was set to the same time setting, but one dropped 27g and the other 40g.
We fiddled with the grinder a little bit and finally came to the conclusion that the Mexican bean was just heavier than the Colombian bean. In the same amout of time, more beans were dropping through. I mean, I know different beans have different weights. That correlates to why we like coffee grown high on the mountains. They are denser, which has more flavor. Density also correlates to weight. You may use (rhetorically) 10 big flat beans, but only 5 small dense beans to get the weight needed for the cup. That is why we brew coffee by weight and not volume.
It all made perfect sense to me. I just had not experienced it in a way that allowed me to directly compare and contrast two beans like that.
***I added a picture of what my grinder looks like. Not sure it is the exact model, but very close.