I meant to say light in regards to roast color of the bean, outside color of the bean isn’t necessarily correlated to the beans total development so alterations of the fan and heat length can develop a bean more than what the outside color would usually indicate or relate to from a different roasting machine.
The spike is like charging hotter in a gas drum, both a non-spike and spike profile still are being “charged” in the first minute to minute and thirty seconds of the roast. But the spike is adding in energy into the beginning of the roast, allowing for a lower overall finishing temp. If a profile used tastes a little underdeveloped in the cup, a 10F/3-4C can help develop those underdeveloped flavors. Maybe you will have to increase the temp more or less, this is something you’ll have to test and taste the results to know.
Too hot of a spike and too hot of an overall profile can lead to tipping (burnt flavor) which will effect the tasting results of some burned and could lead to baked out flavors. Which could be good (or terrible), because if I bake the roast a little, the pastry or wafer like flavor into the roast, it wouldn’t be a terrible cup to drink, think strawberry pop tart or chocolate pastry. If I were to spike within a minute, versus extending the tip of the spike to around 2 or 3 minutes, this will effect how much heat is applied to the bean. And also how much pressure the heat is applying to the bean, the hot air is one force pressing against the bean, while the beans defense is the moisture it is releasing to try and stay cool and protect itself. If I alter the pressure of heat applied or increase fan (an increase a lower pressure environment) I can weaken the counter force of moisture loss (by altering via lowering the evaporation temp of water) coming from the bean, so I can push heat deeper into the bean at a faster rate. Convection is a tricky business because if you lower the pressure and increase the speed of air around the object you can heat the inside much faster than the outside of the bean. Resulting in a much faster roast with a much lighter outside.
We can alter the chemical/flavor results at the end because I am compressing or lengthen the window for the reactants to react how much moisture is left in each segment will change the flavor is by altering heat in certain segments because then I am limiting or creating more reagents to react and produce or reduce more or different flavors. The spike changes how much time I will need to roast and thus alter the window I can roast in to produce the flavors I want. A longer spike will remove more moisture, dig heat deeper into the bean and alter when you want yellow to end and also alter how long brown to development to last and at what rate. I am being vague because there are hundreds, maybe thousands of different coffee greens that you could potential roast that differ in it’s ‘origin’ season/growth, variety, and processing, etc. that will alter how much time or how much heat is needed. A first crack temp can alter by a couple degrees up or down, for the same bean from the same farm but from a different year, or it could hit at exactly the same temp from last year, but you will have to be aware and know this info so you can make adjustments from year to year, or adjust from bean to bean. The further a bean varies from the original bean the more the profile will vary. (That last is an assumption that is slowly becoming a fact in my eyes) There are many variations and I only roast for my own consumption and learning, I don’t roast purely to test theories so I am moving slower than if I were to be running a lab doing profile experiments and cupping all day, so my understanding is though my own experimentation and reading what others have wrote.
This is the closest version of the Marshal Etheo profile that I have, lost and recovered from memory. This profile has a cooling fan of 85% which you might want to change. I remember vaguely that originally 1C happened around 9:30ish but I’ll have to dig through some notes for two years ago.
‘Marshal etheo 1fan80%’ freshly roasted by @ikawahome
, here’s the recipe