If you want a particular ratio of Development time for your "ideal profile" because you're trying to follow Scott Rao's advice, or for any other reason, you'll want to calculate the ratios ahead of time.

You have to start by assigning some values -- hopefully based on experience. Since we're using Development time as a our variable, we'll have to fix the total elapsed roasting time from Charge to 1stCs (i.e., Drying + Ramp). Then choose desired Development percentage. By way of example, let's say you're comfortable with 10min from Charge to 1stCs and want a 20% Development ratio, and call the Development time "x."

x = (Proposed Development Ratio) * (Proposed Time Before Development + x)
x = 20% of (10min + x)
x= (0.2) * (10min + x)
x = 2min + 0.2x
.8x = 2min
x = 2min 30sec

Continuing with the theme, let's look at the same pre-crack elapsed time of 10min, but a 25% Development ratio and calculate Development time -- but this time, I'm not going to show every step.

x = (0.25) * (10min + x)
.75x = 2.5min
x = 3min 20sec

For the proposed Drying + Ramp of 10min, a Rao approved 20% - 25% Development ratio for it would be between 2:30 and 3:20 -- giving a total roast times between 12:30 and 13:20.

If that 50sec difference seems like either a little or a lot of slack, look at it as a controlled Development RoR going from a couple of seconds past 1stCe to a couple of seconds before 2dCs. That's usually around 40F, which means an average RoR after 1stCe of around 8F/min -- and at a typical RoR of 10F/min at 1stCe and an RoR of 6F/min anticipating 2dCs, fits nicely with the technique of "declining RoR," as well as with the intuitive inference that a darker finish should take longer than a lighter one.

Rich

Next version of Artisan will allow you to display the Rao's-percentages during a roast such that you can just stop between 20% and 25%. No need to pre-calculate this anymore.

Markos,

The crux of artisanal roasting is knowing what you'll do before doing it. Artisanal roasting is planning and execution. Artisanal roasting means every parameter should be pre-calculated to the greatest extent possible; to plan the profile ahead in order to hit the intermediate intervals at their proper times, then Drop at the desired intersection of the particular ratio, bean temperature, Development ratio air-flow, total time, RoR, etc.

Another point -- which a mere expression of ratio fails to adderess -- is that the ratio rule must be applied intelligently for the situation. While a 25% ratio might be appropriate for an SHG bean taken to FC, it would bake the hell out of a soft bean taken to C.

Rich

I know we're doing the same math, but for a quick calculation (for a 20% development time, for example):
where t_d is post-1C development time, and t_f is the time to the start of first crack.

Using your example:

Very cool Marko!

Chris,

elltydd wrote:I know we're doing the same math...

Sure thing. Identity Principle, and all that.

It occurred to me that the October Roast and Learn is likely to be very popular with people who are also interested in learning to apply the lessons taught by Scott Rao in his Coffee Roaster's Companion. One of the weaknesses of the Companion for amateur, home roast masters without a lot of roasting experience is its lack of instruction in how to implement a profile the roast master chose for the particular bean and particular roaster.

Development time as a ratio (range) of total roast time seemed like a good place and particularly suited to its own thread (as opposed to taking up in the middle of an R & L thread) for a lot of reasons.

It looks like both of us have developed the bad habit of explaining our reasoning and "showing all work," and made this a little more mathy and complicated than it could be. Maybe the easiest expression of Scott Rao's preferred Development ratio range would be to omit the reasoning, the steps, and cut to the darn chase:

Golden Ratio Development time is between 1/4 and 1/3 of elapsed time from Charge to 1stCs.

Rich

I just created a table so I can use it for planning as well as a reference during the roast for those rare occasions when everything doesn't go exactly as planned

boar_d_laze wrote: It looks like both of us have developed the bad habit of explaining our reasoning and "showing all work," and made this a little more mathy and complicated than it could be. Maybe the easiest expression of Scott Rao's preferred Development ratio range would be to omit the reasoning, the steps, and cut to the darn chase:

Golden Ratio Development time is between 1/4 and 1/3 of elapsed time from Charge to 1stCs.

I agree, I think its a more intuitive description of the ratio, and one that you can calculate in your head on the fly if needed. And hey, I don't think its such a bad habit, especially if it leads to a succinct conclusion like this

Is the golden ratio actually hidden in here or is the term being misused?

Is the claim that the ideal break point with respect to total roast time to development time is at the actual golden ratio or is it just being used to mean a good ratio. Given how precise we try to use language here (comparable examples are that we'd never refer to French Press as espresso or say dose 22g's if we really mean 14g's) it wouldn't make sense to use it just to mean a nice ratio.

If the claim is that the golden ratio really is relevant to roasting that would be quite interesting.

Well, what Scott says is that it would be preferable to not use the term "development phase", but "development ratio" instead. Furthermore, that if the "time from onset of first crack to the end of the roast" does not fall within the range of 20% to 25%, the roast will be suboptimal - either underdeveloped or baked. He further suggests that the actual optimal ratio may be much narrower than this 20% to 25%.
I guess this should be taken as part of the whole, which, in Scott's book would include being sure to start the roast with "adequate energy" and maintaining a rate of rise that is always decelerating throughout the roast.