I roasted some Papua New Guinea AA Sigri Plantation yesterday.

The profile ramps looked as usual, however as i reached ~385F, the typical 1C start temp on my setup, i could only hear maybe a snap or 2... temp was increasing at ~12-15F/min. I ended roast at 425F BT, 3min after.

Second roast, i came in with a little higher MET to 1C, still same thing... 1 snap or 2, and then went silent... this time, i let it go to 430BT, when i heard 2C snaps start (3.5 min past the 1C silent start).

So my question is:

it's normal for some coffees? or should i change something to make 1C more audible?

I had two different 1b bags of some Sumatras from sweet marias, each roasted in 150g batches in a Gene Cafe. I never once heard FC for those. I also didnt like the espresso it made. Maybe its because the roast was off or maybe I dont like Sumatra. I'v not had a problem hearing FC for anyother blend or SO so maybe some beans just have a quiet FC.

Interesting. I had a bit of Sweet Maria's Aceh Sumatra left over from last year's roasting competition that I just roasted a couple of days ago, and I didn't hear first crack either.

Aside from the obvious problems (machine noise making it hard to hear cracks; decrepit middle-aged hearing), the intensity and sound volume of the cracks varies with the coffee. I have never had a coffee where I absolutely could not hear the cracks, but I have had coffees where it required some careful listening. In general, 2nd crack is harder to hear and appreciate than is first crack. I don't roast into 2nd crack very often, so perhaps that is why I have more difficulty hearing it.

ken

Have a Gene Cafe. Use new style exhaust with a 3" diameter X 45" flexible metal duct installed which I use out laundry room window in winter. This really super magnifies sound. No trouble hearing Burman's Sumatra Royal Select Decaf this weekend on back deck. But the Hawaiian Yellow Caturra Decaf? No way. You can easily put your ear in slipstream and the metal magnifies sound. Only way to know Caturra was cracking was smoke. Actually caused me to take Caturra too deep, darn it. Knew it was cracking and strained to hear, still no sound.
Unless I hear cracks, tend to over roast every time and decaf is so much more sensitive.

And have noticed thru the years that all decafs have a very muted crack compared to non-decaf.

I also have the new exhaust and dryer hose going to a cardboard piece I stick in the window with a hole to vent through. Works great, no smoke inside at all. I also have a foil covered bit of cardboard that goes in front to cover the gap between the clear shield and the body. I read somewhere that this helps block extraneous noise so you can hear cracks better and I do think it helps. Despite this, I was not able to hear the sumatra cracks. I usually have no problems hearing them unless distracted, my roasts never seem to turn out great when having wine with my girlfriend. Thats what you get with multitasking i guess. Decaf is always difficult for me too, but i have not roasted enough to get a real feel for it.

Some coffees seem to have very little first crack. I think it may be due to lower moisture content in at least some cases. I had a Yemen Mokha Ismaili a few years ago that did this. I added nine grams of water to 450 grams of coffee (+2%) and put it in a sealed jar in the refrigerator for a few days as a test. When I roasted it, the first crack was significantly more pronounced. Easy to try, in any case.

Best,
David

Silent first crack is fairly common if not normal for peaberries. Other coffees as well. It certainly does make it difficult at times but the best bet is to go by bean color and roasting scents, as well as the cracks. Some roaster setups will make this more difficult sadly.

Try shortening your time to the first, a faster ramp using more temperature early on and see if that changes anything, ~12-15F/min seems a little slow