Roasting slow-fast profile in the KKTO

[readeral]

So the problem is that despite getting ET close to the limit (I find that ET greater than about 270 C causes ashiness and scorching) that you still can't get enough energy into the system. How is airflow controlled in a KKTO? If I had the same problems on a drum roaster I'd increase airflow and raise gas to get same ET but higher system energy.

So there's just a central fan that sits above the whole system, not behind the heat source, but "inside" it (hard to describe) pushing it out to the perimeter of the chamber and circling it round. It's indirect, so ultimately probably terrible airflow in traditional terms. I've been convinced for some time that the airflow is significantly ineffective.

[kwantfm]

You beat me to it. 265 preheat is incredible to me. Again using a drum I preheat to about 180 and even lower when I'm roasting for pour over.

[kwantfm]

So the problem is that despite getting ET close to the limit (I find that ET greater than about 270 C causes ashiness and scorching) that you still can't get enough energy into the system. How is airflow controlled in a KKTO? If I had the same problems on a drum roaster I'd increase airflow and raise gas to get same ET but higher system energy.

[readeral]

Previously my drying was only 5 or so minutes, but that's with a preheat of 265 degrees. The suggestion above was that my drying was (proportionally) too fast then. It just doesn't seem I can get much momentum in this roaster without terribly high temperatures. Probably cause it does such a good job of distributing that heat evenly throughout the system. Maybe I'll dare to tweak how the fan works to get more direct heat onto my beans.

[kwantfm]

Oh, and very sorry to hear you describe your "depressing day of roasting ". We've all been there! I've produced kilos of ash.

[readeral]

Probably could go less, but general convention in previous threads suggests 400g is the lower range for proper bean agitation and avoiding scorching the beans.

[kwantfm]

I have no experience with the KKTO but have used two different drum roasters, so apologies for the really basic questions. First question is why 400 g is the smallest charge you can use? When I was reading about your problems it immediately sounded like they should be fixable by lowering charge weight. The very slow move to dry (I consider 6 minutes as slow as I'd want and with smaller charges I get there in 4 minutes) and the inability to get the system temp through 1C and beyond sound exactly like charge weight is too high.

[readeral]

I'm almost at the point of giving up on the KKTO. Almost. Invested hundreds of hours into building the roaster and trying to get a roast that I'm close to satisfied with (granted I'll never be thoroughly satisfied. That's the game of any sort of skill), but I rarely see one!

I did 4 roasts today to try to nail this slow fast process. I'll upload the graphs of the first 3.. They were "ok". First two roasts were 500 grams and the third was 400g. My last roast I tried 600g which is what I used to do back when I preheated high and left it high, and managed to have the most uneven roast I've had for a long time, with many burnt beans. Needless to say, new approach does not do kindly with larger batches.

My biggest concern on my first roast was that with an ET of 200 degrees, I wasn't approaching end of drying phase before 8 or so minutes, and so started my ramp before drying was over. I tried ramping over 5 minutes to 255, and eventually pushed it to 265 to try to get a better run up to 1C. It fell short, and in doing so, I then didn't have enough energy to push it through to first crack (206 degrees) let alone much beyond it.



In my second roast, I tried an ET preheat of 210, and ramping earlier, letting the machine just ramp as quickly as possible. This was slightly better, and first crack appeared to come earlier (203), but again I had to give it a further boost before 1C and I couldn't get it much past a light roast after backing off from my elevated ET.

My third roast I dropped down to 400g (probably the minimum volume I can get away with in this system) to try and give myself access to more energy. I also decided that instead of worrying about what the ET was, I would try to maintain some sort of steady RoR. This was probably the most successful of them all in terms of how dark I could take it - finally an espresso-worthy roast if judging by temperature alone - but 1C came really late (214), and I didn't develop much beyond this temperature.

Every roast had some ashy beans.

I'll cup all the roasts tomorrow, but I doubt any of them will have that fruity acidity I had last week. What a depressing day of roasting.

[DesigningByCoffee]

I call it the drop zone. I basically preheat the corretto, drop the beans in cold at a certain preheat temp (120-140°), and then the zone from load to the TP is the drop zone (sure it has an official name ). I keep the gun running gently at different temps in this zone to get a consistent TP, but at around 40°. Seems to work for me

Could the probe be moving? If you change batch size, you might need to adjust the probe. I have two locations for 350g and 750g batches - get it wrong and it reads 10° out.

I think your right about ET - lower at the start, hit it harder late. If it is too high early, you're more likely to scorch and tips beans (though I've never experienced this myself!) so might be talking out of my hat!

Matt

[readeral]

Cool thanks Matt - I just wrote a reply but not sure where it's gone...

What is 'drop zone'? Re: my turning point, I usually aim for a consistent TP of 80 degrees after 1 minute. My probe is one of Andy's 100mm probes, 3mm wide, so it's pretty quick responding. Alas, I think I've killed it as where FC used to be 200 degrees, it then shifted to 205 degrees, and now it's 206-208 degrees.

Looking back over Steve's comments, I can see that he was trying to get me to avoid hitting my max ET early in the roast. By ramping right from the start, I still hit my max ET four or so minutes out from first crack. I'm assuming that by delaying my ramp up, I can get better momentum into first crack for a more rigorous crack, as well as avoiding those high environment temperature negatives, damaged beans from earlier high heat input and hopefully carrying it into post-FC development a lot better.

[DesigningByCoffee]

I tend to keep turning point consistent by adjusting my preheat and 'drop zone' gun temp inputs dependent upon ambient and green bean temps. Then increase the ramp from TP to 1C, and leave the post 1C to 2C zone alone unless roasting for filter.

By your tasting notes, it could be than heat / fan is too hot early on in development. I'd try a slower start (possibly less preheat but certainly post TP heat input) but then increasing higher towards 1C. Beans should be more resilient to higher heat input then

[readeral]

Also (sorry about the spam) but some of my beans (at least in the Rwandan roast) did bulge open - which I've always known is an indicator of too much heat. My question is - is this too much heat when dropped into the roaster, or is it too much heat in general from the environment, once the drying phase is over?

[readeral]

Ok - my next experiments are to:
1. Drop my charge temperature to 190
2. Draw out the drying phase an extra minute, and delay ramping my power levels up until about 1m30s into the roast (rather than right from the get go).
3. Prop open the roaster slightly (haven't worked this out yet - maybe I'll just make more gaps in my rubber seal) to get more airflow out of the system, and hopefully carrying moisture with it.

I'm reading from one of Boot's Roast articles that high moisture content requires careful drying phase, and that poor air pressure (and I expect that a closed environment like the KKTO will have quite poor air pressure, even if it has high air speed) will give baked and flattened flavours, and a dulled acidity. Makes sense. It's an oven designed to bake... Can't say that I've always had a dulled acidity in my KKTO roasts as in the past I've dropped quite light, but I can definitely vouch for the baked flavours which I am constantly fighting against.

The risk of opening up the lip of the roaster is that as the convection air is forced sideways across the face of the glass top, I might just be forcing my hot air out of the roaster from the get go, and lessening what heat energy I have available to actually get my roasts over the first crack line and into proper full development. In the inverse, I'm letting moist air out of the system, avoiding evaporative cooling, and also avoiding a super-hot moist environment damaging the roasting beans.

I remember reading previously about people modifying the fan blade angles of a TO in order to get more airflow straight down (and actually seeing a subsequent decrease in roast times). This might be something for me to look into doing, but given there was no discussion of roast defects (presence or absence of) with reference to those mods, I'm hesitant.

[readeral]

Howdy
It was more that one of those Ethiopian roasts seemed so much longer than all the other origins. I tend to find that Ethiopians tend to best best when roasted from faster to baseline, then the Brasil/Columbians like baseline–slower. Just comparing all those different profiles

So if you wanted to roast faster to baseline, there are different variables you could play with: higher preheat, lower batch volume, less development after first crack, higher heat input across the roast.

My question is, if you were to put these in an order of priority, what would you say?

[readeral]

Ok, so I’ve had a munch on some of the Rwandan beans, and there’s a delightful blueberry flavour! I’ve always known these beans could do it, and I’ve never ever got it which has been what’ driving my obsessive change attempts.
Unfortunately I’ve also detected ashiness and would love some advice on this. My bean mass temp only hit 215 degrees before dropping, and it didn’t get to second crack (nor are the beans oily) so it’s some other thing.
These beans have never burnt on a preheated system set to 265, so I’m inclined to think that charging at 200 degrees is unlikely to have caused my problem either, but that leaves me a little stumped. I may be wrong on both these thoughts however.


It’s hard to tell as this is a bit of a mottled bean anyway, but maybe there is some charring in the seam - but it doesn’t look like I have charring throughout the bean. I’m not quite sure what tweak to make to avoid it.


Here’s the profile I ended up with. It was a 470g green batch, when I’m used to putting 600g green in, so this would likely have played a part as well. With this roast, I couldn’t push it any deeper, even though I was trying to - so didn’t have enough energy into first crack to carry it. I’m playing a balancing game which is proving difficult!