More About Temperature In The Gene Cafe

Gene Cafe - more tips on temperature control

The information below is taken directly from the Coffeetime Forum, when asked the following question in italics.

"I was wondering target temperatures, we didnt really discuss that, of course I havent read the manual yet either (its sitting behind my desk atm). For instance, why did we choose 245 that day, would we change that for a different bean, different ambient temp, etc, or is 245 a good starting point for the time being"

The only answer I can give is experience and knowing those beans particularily well having roasted 100s of kg of them. The guide was written when ambients were relatively low, now we are getting into warmer weather you may have to adjust things a bit….only you will know that as I won't be here to roast in these higher temps.

In general setting the roaster to 245 will ensure it gets hot enough to hit 1st crack and do it properly (not a long, slow, drawn out, half done 1st). Don't worry if the roaster exit air temp never hits 245…in fact you may not want it to with some beans. So if 1st comes at 238, or in warmer weather it might come at 230 and it seems vigorous…it could be worth trying turning down the dial from 245 to 232, so that your just maintaining the temperature a few degrees above where first seemed quite vigorous and not letting it climb all the way to 245…if you don't need to…..then after first prehaps dropping 3-5 degrees more to move to second in a more moderate manner. Effectively a time temperature curve that flattens off.

It's very hard to explain…hence the suggestion for a Friday night roastathon in the meets area (once I am back from Singapore).

The trick to lowering temperature as I keep saying, is not to worry about lowering x degrees from the preset value, but x degrees from the highest temperature reached.. e.g. roaster set to 245, with intention of dropping temp by 5 degrees after 1m of 1st crack. If the roaster only reaches 235 and hits first for 1 min….then you drop to 230….5C less, because dropping to 235 will not do what you intended!

Note: if you want to hold a flat heat imput profile, and the temperature reachs say 235, you have the max temp preset to 245, then to keep the heat imput relatively constant (flat) and prevent the temp increasing or decreasing,….you would probably want to lower the temp to around 237. This is because if you lowered to 235, the heater would probably instantly cut out and not cut in again until around 231 (due to the deadband)….do this at the wrong part of the roast cycle and the reduction of heat input could stall the roast. The wrong part of the roast cycle to make big reductions like this would generally be during the early parts of first crack.