Hi guys.

I bought a Gene Cafe a month ago so I am still pretty new at this. My mate said that I should get a Variac to help with the roast, which I did and I seem to have more control over the roast.

The one thing I cant understand is why most of my beans come out looking like this:


It was an El Salvador.

I heated up till 240 deg C, then dropped the beans in. The temp dropped to 180 and I stayed there for 2 minutes. I went to 190 for a minute and then set the temp on 250 and it reached first crack at 12:30 at 246 deg and I finished the roast at 14:30at 250deg.

This is the only bean that has gotten to this temperature. My Brazil gets to 242 and cracks but this one seems to take a bit longer.

I keep the voltage somewhere between 228v and 235, just depending on how the roast is going. I have heard that you "should" get to first crack between 10:00 and 11:30 mins.

I do a emergency stop and cool the beans on a tray outside and they get to room temp within 2 minutes or so.

Please help because I have heard that this is called cell wall collapse and I have no idea why it is doing it.

How does it taste? I have had some of the ugliest roasts taste fantastic. Misty Valley comes to mind, I could never get that bean to look pretty. I know some one will answer the technical question but don't neglect them taste buds.

I don't know yet, but I'm waiting patiently for it to degas a bit.

Lose the variac. The voltage changes you are making only amount to a 5% power delta. Unless the Gene has DC or synchronous motors, changing the voltages changes the fan and rotation speeds, defeating any power input change.

If you want to use the variac, set it for a constant output.

To get to room temp in 2 minutes without a very strong fan means the beans are not hot. IIRC, I get to room temp in 3 minutes with a desktop fan and to 100°F in 4 without. Note that the HopTop has a small fan that blows cool air through the bottom of the cooling tray.

How much coffee are you loading?

I've used a GC for about four years, using at various stages both a variac and a dimmer. However I did get pretty good results with it just in standard form so I think it is best to start there.

I'd often get beans that had some "blotchiness" on them but were fine in the cup. However what you have seems a little excessive.

Your procedure of preheating to near max then E-stop to drop the beans is what I've done for a long time -- this helps in getting heat into the beans straight up and gives better control. However I drop the temp at 1C (to somewhere in the range 232 to 240C, depending on bean and desired length of time in the final stage) otherwise the roast finishes too quickly (and will run away if the bean mass is high).

It would be good to know (as mentioned) your dosage weight. The appearance of the beans, the fairly long time to first crack, the long period at drop temp before rising, all suggest to me that it may be on the high side. If the bean is chaffy, then a high dosage (eg near 300g) will block the outlet and lead to a temporary heat buildup in the drum (not necessarily reflected in the temp reading as the sensor is on the other side of the outlet) which can affect the beans.

I have had most consistent reults at around 230g.

Re the variac. We have a 3-phase power supply and voltage on the run where I use the GC can often be well over spec, often over 250V. I used the variac to keep it around 240V and not overdraw the heater. If you want to use it for heater control, it need to be wired to the heater itself (which is possible, HRO member "Third Crack" has done it with good results). However as above it is possible to get excellent results without doing any of this.

Another thought. What beans are you using? Hard to tell size from the pic, but if they are Maragogype, they need gentle treatment and I would use a quite different profile.

Hi again

I am using 230grams


This is another pic of the the beans, the right is with the camera flash and the left under my florescent light in the kitchen. I just wanted to give you guys a better pic because I picked a piece of food of my camera lens which is why my the other photo was a bit blurry:)

I dont know what varietal the beans are, I will check up on that.

Come to think of it, the beans did release a lot of chaff and I remember it being backed up over the chaff exit which i guess could have caused a temperature spike.

Thanks for all your responses. I will try a bunch of these suggestions and report back.

from the photo on the right, the beans look mildly charred / scorched

Trying to diagnose roast quality based upon photographs (especially point and shoot photos taken with an on-camera flash) is akin to "eye-cupping;" the analyses you will get are not worth much.

It is possible to do a very bad job at roasting and still have respectable looking beans. Most roast defects that can be visually detected require gross errors in roasting such as a drop temp that is way too high, causing scorching, or improper bean development, where the exterior of the beans looks like it comes from a different (more advanced) part of the roast process in comparison to the volume expansion of the bean that would be expected for that degree of roast.

But all of this requires a keen eye, very careful photography, and a knowledge of the particular bean that has been roasted.

All of this is to say that simply posting typical point and shoot flash photos of a roast product are probably not going to produce useful comments unless you have really very seriously screwed up.

ken

Ken makes a good point, one can get carried away with presumptions

The second set of pics does offer a better perspective. They're not too far off beam visually (and could well be fine in the cup have you tried them?), except for the slight scorching on some. IMHO the drum on the GC just does not get hot enough to scorch beans, so this could be due to running high in the final stages. If I had a result like this, my next try would be as somewhat lower setpoint (say 244 instead of 250) and to reduce to say 240 at 1C. Hopefully that will give at least three minutes before 2C.

However experimentation is needed. I logged quite a few runs to figure out what to reduce to, and how long to to run the final stage, in order to finish slightly before 2C.

Another useful thing to do is break the beans open. They should be reasonably even inside, slight but not too much colour gradation. And also watch for tipping.

Also, I'm pretty sure the Maragogype idea was wrong, they not big enough.