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First crack temperature offset roasting

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  • First crack temperature offset roasting

    Ive done a few roasts with this setup now and have quite a few pages of notes to look back on. When I did this I noticed a really interesting pattern. The first snaps of 2nd crack invariably happen 15-16 deg C above the temp observed for the very first snaps of 1st crack. This is across quite a few very different beans that exhibit a range of temps at which the first snaps of 1st crack occurs (about a 10 deg C range). This is brilliant, as it allows a virtually fly-by-wire approach to roasting. I did a twilight roast the other day and gauged it solely by this temperature offset and sure enough got it just before the start of 2nd crack (ie 1st crack + 14 deg). Ive also racked a few more up with great results, including multi-bean blends. This allows very fine control of the roast degree independent of the lighting conditions. So now my roasts vary in the range of 12-18 deg C from 1st crack, depending on where I want to take it.

    I should note that this offset will probably vary across different corretto setups dependent on where the thermocouple is situated.

    The corretto goes from strength to strength.

    Cheers,

    Mark.

  • #2
    Re: First crack temperature offset roasting


    Interesting observation Mark. Looking back at my extensive notes I find that from first pops of FC to first pops of SC is usually from 15 to 20 C with some variation from bean to bean. With some beans it is 15C from the last pops of the FC. But some beans are harder to distinguish the cracks than others.

    About to do a roast or 3 now so will pay careful attention. If this is so maybe we can roast purely by sound and DMM


    Belinda

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    • #3
      Re: First crack temperature offset roasting

      Well, theres always an exception to any rule and todays Sulawesi Kalossi Toraja may have been it. I couldnt clearly hear 1st crack. I finally decided it was in 1st crack 186 C (which was possibly up to 2 C later than the real onset) so decided to take it to 202 C for a roast slightly past 2nd crack. But then I hit 197 and could definitely hear some cracks and thinking it was 2nd crack I decided to stop at 200 C.

      This is one hard bean to roast. My roast went to 19 22" with 1st crack around 11, but it still came out very uneven and lighter than I was looking for. Maybe my original target of 202 C would have been to go. Even the red sea blend is easier to roast than this one...

      At least Ill have this beans number next time...

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      • #4
        Re: First crack temperature offset roasting

        Originally posted by Sparky link=1181439483/0#2 date=1181469118
        Well, theres always an exception to any rule and todays Sulawesi Kalossi Toraja may have been it. I couldnt clearly hear 1st crack. I finally decided it was in 1st crack 186 C (which was possibly up to 2 C later than the real onset) so decided to take it to 202 C for a roast slightly past 2nd crack. But then I hit 197 and could definitely hear some cracks and thinking it was 2nd crack I decided to stop at 200 C.

        This is one hard bean to roast. My roast went to 19 22" with 1st crack around 11, but it still came out very uneven and lighter than I was looking for. Maybe my original target of 202 C would have been to go. Even the red sea blend is easier to roast than this one...

        At least Ill have this beans number next time...
        The Sulawesi is notorious for its uneven roast. Uneven size and uneven roasts though dont keep it from consistantly being one of my favorites.


        Java "Love that spiciness!" phile
        Toys! I must have new toys!!!

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        • #5
          Re: First crack temperature offset roasting


          I too roasted up the Sulawesi Torajah this afternoon and found it to have one of the loudest 1st cracks of all the beans I roasted. Sounded like a gun going off !!

          1st lasted from 193 to 207 C with 2nd kicking in at about 215C

          It is a very odd looking bean with light ones and some almost black ones in the mix. Finished relatively uneven but not too bad considering. Makes for a long 1st crack, as above.

          Funny there are such differences from one persons roast to another ......................

          I was using my top probe which is about 3 cm from the bottom of the BM bowl. Where is yours Mark?


          Belinda

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          • #6
            Re: First crack temperature offset roasting


            I normally find 1st crack is like a stick snapping. Quite distinct and very audible. This one was more like a 2nd crack and thats why I probably missed the real onset. I remember thinking, "Is that 1st crack?..... nah cant be. Its too quiet.."

            My TC comes in from the side about 1 cm from the bottom. So its near the bottom of the bean mass.

            As my flu abates and my sense of smell returns, the Guatemalan HH that I roasted on Friday is starting to drive me crazy with expectation. It smells awesome. I stopped this one just shy of 2nd crack and it came up daker than the Sulawesi Toraja, even though the latter went into 2nd crack. Odd.

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            • #7
              Re: First crack temperature offset roasting


              I roasted up some Guatemala Huehuetango today as well as the above.

              FC went from 198 to 207 C ish with SC coming in at 211.
              That makes it 13 C from beginning of FC to beginning of SC.

              Also roasted up the Peru Segunda Naturals with FC from 195 to 205 C ish, and SC starting at 212 C.
              That one was 17 C from start of FC to start of SC.

              There is a definite pattern there; +/- 2C from 15C from FC to SC ......


              Belinda

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