How reliable an indicator of sufficient drying, if at all, is the force and duration of 1st crack? In other words, if a roast has a very muted and short first crack, how often can I assume that insufficient drying is the culprit rather than a coffee with a low moisture content?

If the correlation is not solid, then can we make any generalizations about which coffees have unimpressive first cracks but still need normal drying time?

Noah

If old coffees do have a weak first crack, and old coffees lose moisture over time [1], then a weak first crack is more likely a result of too much drying rather than too little.

[1] http://www.sweetmarias.com/green.coffee.freshness.shtml

Maybe? But I decided long ago to just be entertained by 1st crack. Way too many variables.

From my experience the shorter time to first crack for a given coffee the more intense and frequent the snaps are. My vote is overdried = undercrackling. Overdried is overdried if it was via dehydration or heat.

CHAD

At equal degrees of dryness or age or time spent drying prior to first crack, consider the degree of "ramp" at the onset of first. Bringing temp up quickly produces a more robust first than a more gradual increase. Ramp at this point matters a fair amount in the character of the final roast, but I'll not get into unraveling what that might be. I'll defer to the science.

Hopefully reviving an older discussion...

I think that if you remove the variable of the bean origin and green bean age, then yes, first crack should be a good indicator of a successful drying phase.

I say this because first crack is the result of pressure build-up within the bean and the pressure build-up is caused by vaporizing the water trapped inside the bean. If you imagine the changes going on inside the bean; as you heat it, a temperature gradient is formed within the bean. The outer edges are hotter than the core of the bean and as trapped water is vaporized, a vapor wall progresses towards the center, which causes increased pressure, which causes swelling, and eventually first crack, which is the sudden release of water vapor and CO2.

Therefore, if you have a good, robust first crack (again comparatively speaking, considering only the same lot origin and the same green bean age) then I would assume it indicates a good, robust drying period. In other words, I believe the two are tied closely together — but I'm not discounting the "ramp" mentioned by Martin, which is also an important factor to consider in first crack robustness.

Just last week I had a failed roast that went through the usual paces and superficially looked good, but ended up being under-roasted. Looking back at my data I can see that first crack was weak and it all started with an insufficient drying period.

mcwresearch wrote:I say this because first crack is the result of pressure build-up within the bean and the pressure build-up is caused by vaporizing the water trapped inside the bean. If you imagine the changes going on inside the bean; as you heat it, a temperature gradient is formed within the bean. The outer edges are hotter than the core of the bean and as trapped water is vaporized, a vapor wall progresses towards the center, which causes increased pressure, which causes swelling, and eventually first crack, which is the sudden release of water vapor and CO2.

I want to make sure I understood what you wrote. You're basically saying that a shorter than required drying phase causes a weak C1? And that longer drying could empower C1?

I think first crack should indicate how successful your drying phase was. But how it indicates that is something I'm still trying to figure out.

I assume that if your drying phase is too short, you don't develop the proper pressure within the bean and the pressure build-up is what causes first crack. Therefore I would assume insufficient drying phase = reduced pressure buildup = weaker first crack. I don't know if "weaker" means not as loud, or of a shorter duration, later occurrence, at a higher temperature, etc.

But for me this is all based largely on what I've read. I'm still very new to roasting and need to do a better job of phrasing my posts so they don't come across as advice or authoritative. When it comes to roasting, I'm so wet behind the ears I should be wearing a shower cap.

If 1st crack is what most sources claim it is, namely explosive release of (mostly) steam pressure caused by residual moisture, then it's not very plausible that too much moisture would cause a lack or reduction of first crack artifacts. Quite the opposite I think. Sure, it will take higher heat and/or more time to get to 1st, but it has to happen once the pressure reaches the destructive bean-busting threshold. In my setup, I expect to see 1st in the range of BT = 390F to 410F (treat these as arbitrary values relevant only to my setup). If I pass through this range without hearing 1st crack, then I have to assume that my beans were over-dried, either due to age or to crawling up the temperature ramp too slowly. Invariably, steepening the ramp (reducing the warmup time) will result in a more definitive 1st crack. Caveat: I do find that very fresh, unusually damp beans will cause a greater disparity (lag) between my indicated BT and "real BT." In other words, my thermometer will indicate that 1st started at a higher temp (and likely later time) than usual. If your thermometry is dubious (like mine in this case), I can see how it could lead to premature termination of the roast, with an incomplete 1st crack making for a nasty result.

Edit: didn't mean to imply that a vigorous 1st is necessary or even desirable in all cases. I have some, mostly tiny DP beans, that barely register, and they brew just fine.