Thanks for the input, always enjoy trying different roasting approaches! I am always at the window and the tryer. I would consider myself a very active and attentive roaster. With that said, I hate on the huky if you pull the tryer out all the way it dumps beans. I usually am glued to the site glass and have never had trouble smelling things develop.

What charge temp are you using? What is your time to end of dry? What is your over all roast time? What color are you dropping at?

This was a Guat I roasted last week on my vintage 12kg Probat.

Yellow was at 6min/300f
FC was at 9min/360f

Color is a bit on the light side. Apple Juice, Berry, Hibiscus, Brown Sugar/Graham Cracker

keno wrote:I think you might want to try approaching this one like it were a natural processed coffee. Naturals being less dense are much more susceptible to tipping. A good approach to roasting naturals would be to charge at a lower temperature and use more air early in the roast, use a gentler slower ramp, and back off the heat a lot in development and use a shorter development time. Good luck and let us know how it goes.

treq10 wrote:Recently, I had to troubleshoot some tipping issues on longer roasts, both for very dense coffees. One a 1900m Rwanda washed, the other a 2000m Ethiopian Natural.

After my tests, I'm convinced that much of tipping is due to two main factors:

1. Inefficient/long dry which results in the thinner parts of the bean (aka the tip) drying faster than the denser core, which leads to:
2. Application of heat greater than the beans can take at any given point during ramp/FC/post FC.

The solution to this is that, given a fixed total roast time (this depends on your desired flavor profile), you want to ensure that most of your energy is put into your coffee during the charge + turn. What this allows is an efficient dry with enough momentum during ramp/FC to allow you to apply no more than the necessary heat setting to get full development (lower the better, though never too low aka stall/underdevelopment).

For more body/complexity (especially for espresso), a longer yellow/maillard stage is desired. It's very tricky to attain this, and the key is to find the RoR that during maillard and development that allows you to keep a very steady & appropriate heat throughout the roast. If you find yourself constantly fiddling with your heat and ending up beyond your burn point, you will almost always have scorching or tipping whether it's visible or not.

I agree and believe that lengthening the yellow also decreases/narrows the window for optimal dropping time.

imo, tipping is caused from the "expanse" phase, where the beans expand but it is not quite 1C yet, and so to rast a ramp to first causes this. 1st and second crack sound is caused from the internal bean splitting like in your pic, but the outside vs inside has to do with heat/air/fan/drum rotation. internal sourcing can be caused if these variables cause cooking to happen and are also affected by these factors during green to pale and yellowing.

I roast on a 1k machine and I've noticed tipping usually from too much air. You mention that you use the max (basically, lighter blows out) later in the roast. Airflow and heat have to work together and you could be using too much for that coffee. Try something slightly higher initially and slightly lower later on if you decide to adjust the fan at all. On smaller machines using a constant air speed can simplify the adjustments needed as airflow adjustments can have dramatic effects. You'll also need more BTUs of heat input if your air is very high at any point which isn't roasting it gently. It's possibly to roast relatively fast and still be gentle. Too much heat from high airflow can look right on probes but causes roast defects. Slower air and lower heat can produce the same RoR as more of both until you fall under max efficiency for the volume of air.

Basically if we had a way to equate proper settings for a given coffee with 3 settings... air/heat 1 low, 2 mid, 3 high

2/2 = best heat transfer efficiency for that coffee
3/1 = cooler drum, temp crashes maybe, long roasts
1/3 = hot drum, slow energy to coffee, defects would be apparent early in roast (scorching/facing)
3/3 = normal drum temp, probes read like 2/2, air carrying heat to fast, defects show mid to late in roast (tipping)

The heat and air needed for each coffee may vary slightly but your probes won't tell you if you're using less than ideal heat and air settings.Try to approach it one variable at a time and you'll see an improvement. Hopefully that is understandable. I have trouble putting thoughts into the right words sometimes and understanding the physics of roasting is technical and can be hard to explain depending on the person receiving the info.