"Nonexistence of Heat Momentum"
Okay, I get it. As a novice roaster, I'm still finding my way, and asked for guidance in that thread. DaveC wrote a thought-provoking response that helps me think about roasting in some new ways. The thread continued with a tight focus, so I opened this thread to follow on with Dave's concepts and others that experienced roasters may offer.
drgary wrote:What factors are most useful to you in planning and controlling a roast?
Can you suggest terminology that better describes what home roasters can track with a roaster that accumulates energy that is being transferred to the beans?
Is the instrumental calculation of steadily declining ROR useful in any way, depending on the device? Is it distracting from more useful concepts? Or, would it be better to replace that concept by referencing a few other guidelines to help people avoid uneven roasts, stalls and runaways?
My next post presents follow-up questions about some of Dave's principles.DaveC wrote:factors most useful in planning and controlling a roast:
1. A good understanding of the particular bean being roasted and how it reacts. If it's a new bean, but of the same type/varietal/region, then experience will help when planning the roast. e.g Some beans have a quiet 1st, more heat into 1st may make it louder but for that bean will be bad, others may have a louder first than usual, reducing heat into first for that bean may be bad. you need to know your bean.
2. Knowing your roaster really well and forward thinking the roast. When something happens not in line with the roast log for that same bean, be alive to the reasons why, what's happening with this roast that's different. lower voltage, gas pressure, crosswind on exit vent, lack of cleaning and clogged fan etc..
3. Forward thinking is forecasting what you think will happen in 3 or 4 minutes time, because the larger the roaster, the earlier you have to take action.
4. Understanding the effect different processing methods make on the approach to roasting a particular bean in your roaster. e.g. I had an Ethiopian Longberry Harrar I could roast in 13.5 minutes, or 15 minutes...extending the roast in a particular phase. The shorter roast no blueberry to speak of...the longer roast, bursting with blueberry,
5. Realising the Maillard reaction with monosaccharides actually has a very small window and if you rush through it, you may not get the flavour complexity you want. So fully understand roasting chemistry, especially the temps at which various compunds are formed, destroyed and at which certain reactions take place.
6. Knowing your probes and what they are really telling you.
7. Drive it well manually before using computers...if this wasn't the case Pilots would press buttons and we would have no need for Joysticks. They would never have to learn how to actually fly. Same thing with roasting. Plus roasting with a computer gives repeatability, but no awareness, sometimes no excellence. You still have to understand what's happening.
8. Use as little airflow and heat as you need to achieve what you want...I realise this may sound stupid but coffee doesn't like lots of heat or lots of air. e.g. Depending on the roaster type, if you want to slow the roast (not on some roasters), lower the energy input, don't pull more air. Of course not having sufficient airflow is just as bad as too much, but in a different way. Many drum roasters are best controlled by leaving the air alone and controlling heat input.
9. With an electric roaster, always measure the thermal energy you are using, watts are watts and give a common frame of reference.