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Today we fired up the roaster for good.

by | Dec 16, 2011 | 0 comments

Today we fired up the roaster for good.  We started off by heating the machine up to 180degC.  As soon as both the environment and drum thermocouples agreed, we dumped the first batch of test beans.

For some reason, I wasn’t able to get the gas pressure above 0.8 mBar.  I think it might be our rather dated pressure regulator, so a new one will be installed on Monday.  Regardless, the burners are more than big enough and we managed the first batch of 4.8kg in about 14 minutes.  The standard regulator will allow for 2.8kPa, so we’ll have more than enough power to play with.

The second and third batches went just as well.  I toyed with the pressure to see how fast I can change the air temperature, and what effect it has on the system.  I was really impressed with having readouts on both air and bean temp.  The air temp allows you to judge what the bean temp will do well in advance, and I was able to see just how volatile the roasting chamber’s temperatures really are.  Even small gas changes reflected in the air temp within 5 seconds.

The last batch of the day was a Bromelia Fancy.  We started with a dump temp of 190degC.  I turned the heat to full power and reached a Turning Point (TP) at 85degC.  The hard beans were reluctant to take up any heat, but I pushed through while playing around with the pressure some more.  The air temp peaked at 250degC, whereafter I reduced it through first crack and let the beans’ thermal mass carry the roast through to second crack.  I dumped at 222degC, 16 minutes into the roast.  A little longer than I usually roast, but considering my gas pressure restriction and the hard beans, it came out very, very nice.

On Monday, we’ll do the same thing again.  Then we cup, cup and cup again!

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