I've been roasting for about a month now - I do it in popcorn poppers and in a rotisserie drum. Suddenly my last several roasts have been not smelling like fresh roast coffee. I've had this problem with Panama Carmen Siete Dias de Bellota, Liquid Amber and a blend of Brazil, Ethiopia, Yeman and Panama. Right from the start and even after several days of rest all of these roasts have an off smell - almost chemical in nature - maybe a little sour smelling. I'll appreciate any advice you might give me. Even in the past when I over roasted in the rotisserie drum and the coffee had a somewhat burnt smell at first, after a few days of rest, it seemed to mellow out and smell pretty good. I have changed my process somewhat and tried to go for a little longer roasts - is this what under roasted or baked coffee would smell like? I need help. Thanks.
dickc

"Off smell, almost chemical" isn't a very precise descriptor.
-- Buy some good coffee from one of the roasters we talk about here, preferably at the same roast level you normally use. Grind it, and grind some of your coffees, smell. Whats the first word that comes into your head? -- Brew the coffee, let it cool for 10 minutes, and taste. Now what are the first words?

Questions:
Is the of smell from both roasters, or just the rotisserie? Do you use it to do other sorts of grilling?
How far do you roast, end of first crack, start of 2nd, end of 2nd?

Thanks for the reply Jim. I've done all you suggest. I've had good coffees from PT's, Paradise, Intelligentsia, and Metropolitan. The thing is I've had good roasts from both my popper and my grill. Then all of a sudden I get this non-coffee smell. From both methods and I've done nothing except try to slow my roast down and try for a lighter roast. My first thought when I smell and taste the pros' stuff is "this is sweet smelling, a little like burnt caramel and, well, coffee smelling and nutty. This stuff is bitter and acrid smelling. After devoting some real effort at describing the smell better, I'd say the Panama, which was roasted in a popper, smells a little like stale wine, while the Liquid Amber, which I roasted in a drum on the rotisserie, smells a little more like stale smoke with maybe a background of that stale wine. Again, I've had other roasts in these same devices taken to the same degree of darkness that smelled like coffee - these don't. That's about as good as I can do - I have done a few more roasts the last few days and am interested to see if I can overcome the problem. I was just hoping my somewhat inadequate description would be easy for someone to spot - like Panama is supposed to smell like that or that's clearly a smell associated with under roasted coffee. I guess for me good coffee is like the Supreme Court said about obscenity. I know it when I smell it.

Are the beans 5+ days old yet and if so how do they smell now? If this is the first time you've done a significantly lighter roast in awhile I find lighter roast do have more off smells for the first few days. Otherwise you need to describe your roasting profile and approach a little more to possibly figure it out. level,times, power adjustments

Way, way better on the descriptions, but with a few turns of phrase that are so original I don't understand them.

If by "stale wine" you means like vinegar, you roasted too light; you get vinegary aromatics in roasts until a little beyond the first crack. Try sniffing the smoke when you roast. In a light roast, you'll catch the vinegar smells until some point after the first crack ends. Wait a little longer for the first hint of caramel to creep into the smoke, and you're done for a light brewing roast.

"Stale smoke" sounds like walking into a room with an all night poker game that's gone on too long. If that's what you meant, you over-dried the beans, going too slowly from your drop in (or cold start on the popper) to about 300F, when the beans go from green to yellow and the roast starts.

Since you're getting these faults on both roasters, it eliminates some non-coffee factor being the culprit. So my first guess is you may have pushed the light and slow roast envelope a little too hard.

Thanks again. This whole process has probably revealed some of my character defects. First, I try to reinvent the wheel by using my own terms. I'll try to do better at using terms others use. And, secondly, I was impatient. So, I'll address the impatience first. When I noticed this aroma issue, I started roasting several different kinds of beans. I roasted 8 oz. batches in my 1 pound drum on my rotisserie and I roasted 1/2 cup batches in my 2 poppers - 1 a 1200 watt Toastmaster and one a 1400 watt Wearever Popcorn pumper. The Panama beans I roasted in the 1200 watt popper from a cold start. I got 1st crack at 5 minutes, stopped roast at 7 minutes, infrared thermometer reading of 430 degrees. I thought it looked like City+. I followed this with a second roast in the same popper. Got 1st crack at 4 minutes. I stopped this roast at 5 minutes, 50 seconds at what my infrared thermometer showed as 425 degrees. I thought this would be a City roast. In fact it looked the same to me as the 1st roast - a little darker than I thought City should be. I did these roasts on 9/4 and until today these roasts did not smell good to me. Today, they smell better. So I think the resting has helped. Although, I went down to the local grocery that carries Intelligentsia beans and picked up a bag of 5 day old roasted Central American beans. These helped me reset my aroma senser I think. Now I think they smell like smoked raisins. And a little like smoked hershey's dark cocoa. (I also stuck my nose in a container of that to help my point of reference). Although, I do suspect these roasts took a little long to get to 1st crack and that preheating the popper might help. Do you suppose that I just don't like this particular coffee? I'll taste it again tomorrow to see if the taste has advanced along with the aroma. Another question I have about aroma of coffee as it relates to taste is: Can it be like cheese? I mean can the aroma be off putting while the taste is enjoyable?

The Liquid Amber I was concerned about I roasted in a 1 pound drum on my Weber Spirit grill. I roasted this on 9/3. Here's how I did it. I preheat the grill - not the drum. I used 2 thermometers - the Weber that's on the top of the grill and a digital that I got from Sweet Maria's. I position the thermocouple on the digital so that it's at the level of the beans in the drum although obviously it is outside the drum.
So when the Weber read 380, the digital read 470 I loaded the drum in the grill. I was back to 500 degrees on the digital within a minute after loading. At 5 minutes I had good sweet smelling aroma from the grill and showed 440 degrees on the weber and 570 on the digital. 1st crack started at 12 minutes, 15 seconds with 440 degrees on the weber and 585 on the digital. At 13m 15s I showed 450 on the Weber and 600 on the digital. I turned the gas down slightly at 15minutes. at 16m 45s I showed digital temperature of 530. I I I think I started second crack at 17m 30s and stopped the roast. I had pretty good smoke and the roast looked like a pretty even light Vienna. I was pleased at that time. But after 3 days, it didn't smell sweet or caramely or chocolatey it smelled like that bar room where people had been smoking all night - maybe like an old ash tray, maybe a little like leather - an old baseball mitt. And it had a harsh taste dominated by that old ash tray smell. Today though, it smells sweet and made a great espresso with lots of crema and tasted mainly of bittersweet chocolate, and, of course, some smoke.
So, I've learned to wait a little longer. But also in addition to warming up my popcorn poppers before a roast, for my grill, I'm thinking I should try to finish my roast in 15 minutes. So my plan is to preheat the grill to 475 on the weber thermometer, which will probably be around 650 on the digital. I would expect 1st crack then in somewhere between 6 and 10 minutes. Then after 1st crack, I have read some different recommendations, but I'm thinking I should try to slow down the move to 2nd crack so I'll reduce the temperature but try to finish in less than 15 minutes.

Your popper roasts will be grassy. Reduce the dose (by weight) until it takes around 5 minutes to get to the first crack, and around 8 to 10 minutes to finish a roast.

The drum I can't tell. Do whatever necessary to get roasts that last around 10 to 15 minutes overall, that run at least 3 minutes from the start of the first crack to the end of a light brewing roast, and at least 4 minutes for a medium espresso roast, and that aren't scorched. Get the "how-tos" from someone with the same or similar rig.

Sumatras and Monsooned Malabars, major ingredients in Liquid amber, can smell like a sewer; the other major ingredient, Harar, can smell fermented, either with rotgut style like acetones, or pickled smells like sauerkraut and hot dogs. It's not advisable to do blends with these coffees at very light roasts unless you also enjoy the smell of cheese