readeral's KKTO

[Dimal]

Worth a try mate....

With a Corretto for example, there is absolutely negligible benefit to preheating the Bread Pan, as the thermal mass is so low that the bean mass, once introduced, brings the temperature down to just above the bean mass temperature after introduction.

With the KKTO, there is much more thermal mass available, so the concept of post introduction of the beans to a preheated roaster, does make some sense. It's been a while since I was able to play around with a KKTO so I can't remember what the Inner Bowl mass was, I don't think it was all that much but it should be able to buffer the 'rate of rise' of the bean mass enough, such that you should be able to avoid tipping or scorching.

Will be interesting to read how you get on...

Mal.

[readeral]

Thanks Mal. I've read a few of Boot's articles floating around, although he does keep his cards close to his chest, his roasting defect articles have been great, so it's handy to be pushed back in that direction for some much needed revision. Chatting to a mate at a cafe down here confirmed my thoughts about reducing charge temp so I'll give that a go next roast.

I know it's dangerous to question the status quo, but I'm going to float an idea anyway. This is only a thought experiment presently, and far too impractical to do anything about right now.

I received Rao's book on roasting for Christmas (if you are reading this and want to bash the book, I'm not interested, sorry. Do that in another thread) and been enjoying his fleshing out of my skeletal knowledge. One thing that intrigued me as I was reading through his description of various roasters was his explanation of the "Classic" drum and double drum designs. The KKTO strikes me as (forgive the comparison) being as close to a double drum in physical build as any other "traditional" roaster. However this description falls down as the method of heating the whole chamber is entirely not like a double drum, but the heat comes directly to the beans, more like a fluid roaster.
Rao gives some pros and cons (and any other observant roaster could tell you the same) that the downside of of the classic drum is that overheating the metal "can easily lead to bean-surface burning".

I was heating my roaster quite high (to a stable temperature, not a few minute burst at high heat) in order to try to generate more conductive/radiant heat to balance the convection airflow, and reduce the amount of energy going into the roaster's metal during the roast, rather than the beans. In doing so carelessly, I was gaining all the downsides of the classic drum design, without its indirect heat benefits. So... After that long winded fluff, I'm thinking of what the impact might be of preheating the outer pot of the KKTO, without the roasting chamber inside, and "charging" the roaster by inserting the chamber quickly with the beans already inside it, thus gaining the benefit of the radiating heat from the already preheated chamber, without the downside of room temperature beans being poured directly onto a 150-200 degree surface and tipping/scorching, mimicking somewhat the way a traditional roasting chamber will quickly make the beans inside it airborne, avoiding the same issue. Anyway - just some thoughts to mull over!

To be practical, a KKTO roaster really wouldn't be able to manage the (stable) high charge temps that traditional roasters manage without some sort of roasting defect.

[Dimal]

Some good info to be found here and in other articles in and around the website mate...

http://www.roastmagazine.com/resourc...RoastGetIt.pdf



Mal.

[readeral]

Ok so tonight I roasted 750 grams of a Brazil bean. 15 degrees outside.

Preheated to a steady 150 degrees. At charge I upped the temperature to 200, at 2 minutes to 220, and at 6 minutes to 250 (you can see this knee in my graph, but it was right on the cusp of the development stage, so I wasn't too worried) - from this point on I didn't touch anything. I had a turning point of 63.3 degrees 1:10 into the roast.

After hitting around 170 degrees in bean temp, the RoR took a small dive - makes sense, the TO had started to heat the drum again as well as the beans. It recovered a little before continuing it's slow downward progression.

The RoR increased (as expected I suppose) at 1c, but by this point I was teetering on the edge of a RoR of 1.5 degrees/minute so wasn't inclined to play around with the dial - but I should have because it rose up to 3 degrees/minute and plateaued there almost until I dumped the beans at 212 degrees at 26 1/2 minutes.

Here's my graph:


So the result? Well sure it was a much more even roast - I put that down to the increase charge weight (probably) allowing beans to experience a full range of exposure. But I still have tipping (or is it scorching - I'm not sure. Basically overdone right at the tip of the bean). Sorry, no pics, no natural light to photograph and I've bagged them all up.

So where does this tipping come from? Too high a charge temp? An uneven mixing action? Hot spots on my roasting chamber? Too high MET? I'm not sure. Maybe a combination of all of them. It's not only a few beans, although not being all it does permeate the roast - so I suspect it's possibly a temp of drum issue, but in that case I'd have expected to see scorch spots on the body of the bean as well, which I'm not.

It might be from the increased RoR at the end there, but I was having a look into the chamber as best I could, and I thought I saw it appear before that flick at the end.

The greens are fine - I took delivery of them 2 weeks ago. Haven't got a density measurement, but I'm sure they're not dry.

Part of me wonders that if I had a solid agitator, I'd be able to toss the beans around a little bit more like a traditional roaster and so better move them out of contact with each other and the drum. I don't know. I'm also wondering about airflow - maybe my TO doesn't extract as much air as some of the older models that snobs are using. So many variables - probably barely any of them matter - but I still need to solve my tipping issue.

Anyone who has experienced it in a KKTO and successfully resolved the issue is particularly welcome to comment, although ideas from anyone would be great.

[readeral]

Yeah so that's what I think I was pushing back against KK - I'm not convinced that (for example) my KKTO wants a 250 degree 5 minute preheat, cause my RoR after loading at that temp is upwards of 30 degrees/minute. My best experience has been a preheat to 150 degrees, but with the whole roaster stable at that temperature.

Absolute statements like "X approach is always best" gets my back up. I'm sure my roaster will behave differently to others.

I'm hearing you on the charge size Bosco, and I appreciate the suggestion - I'll increase the charge to 800g and I'm sure I'll get a much more evened out roast given what you've said - but I still want to know what's going on, and I wouldn't say that keeping records means I'm trying to run before walking. Incidentally, I'm still putting 600 grams in, it's not like these are disastrously small batches or anything. In my conversations with KK and then with other KKTO owners, 600 grams seemed a reasonable starting point, and my method was learned from the info I received from KK. KKs documentation recommended starting with 450g charge, and my starting point for method was as follows (verbatim):

Coffee Roasting Method 2 - Roast from hot start
A Digital Multi Meter can be used for accuracy if a specific drop in temperature is wanted


o Pre heat the roaster at 200 deg Celsius for 5 minutes or until all surfaces of the roaster are hot
o Start the roasters agitator
o Add green beans to hot roaster or a pre determined temperature
o Roast in set increments of temperature settings:
- Start at 200 deg Celsius on the dial for up to 2 minutes
- Increase heat to 220 deg Celsius up to 6 minutes
- Increase heat to 250 deg Celsius to first crack
o Only reduce heat after a rolling first crack and to facilitate a longer time to second crack
o Aim to reach second crack in the range of 6 to 8 minutes after first crack

This was a great start for me - I learned a lot about it's behaviour, and I guess my next step is to increase the charge weight.

[Koffee_Kosmo]

The KKTO roaster was designed to handle larger loads It's designed to roast loads of 650 grams to 750 grams and above ( roaster chamber volume setting dependent )
Yes it can roast smaller loads but heat control needs to be monitored carefully and check that agitation is also adequate for complete mixing

Also One mans profile using XYZ roaster will not result in the same roast on another roaster Only automation and control of heat source will get close

KK

[Bosco_Lever]

At the moment I'm documenting everything. I'd sooner know how to tweak a roast to get the best out of a bean.

Before you can tweak a roast, the roast has to be drinkable. Tweaking it is by bean weight.
You are trying to run before you walk.
Concentrate on one bean, and learn what your roaster can do at different weights.
Once you have mastered this, you can tweak the roast.

[Bosco_Lever]

I roast in the garage with the door open and adequate ventilation. I do not use a fire blanket. Ambient temp is 22 to 24C.

Your issue (putting it simply and diplomatically) is that you are complicating matters.
Choose one bean, say an Ethiopian, and follow the above method.
Start with 650g, then do the same with 700g, 750g, until you find the sweet spot.
Forget about the length of time of the roast. Just do it and taste.
You will find which load is best.
This is what KK recommends, and my experience concurs.
I do not get any charring or roasty flavours unless the roast goes into rolling second crack territory.
You need to maintain the temp at 250C, and adjust the weight of beans.
You went to the extreme when building your unit, to stop heat escaping, and can probably do 1kg roasts with no issue. Your problems stem from too small a load.

[readeral]

Depends what you mean by "best" and "perfect results". I've followed such an approach and it hasn't yielded results that I'm entirely happy with. Probably in the 'fine' category for some beans, and some beans ended up with charring or very roasty flavours, so there are more variables than temperature and time to consider. Maybe you roast in a closed environment, I'm not sure, wasn't part of your KISS explanation. I don't like to roast as dark as the cusp of 2nd - even though that's the most popular depth around here, so I need to be more careful with my development phase and know when to pull.
At the moment I'm documenting everything. I'd sooner know how to tweak a roast to get the best out of a bean. But I'm still green to this game yet.

[Bosco_Lever]

Simplicity is the key.
Follow the teachings of KK.
Preheat at 250C for five minutes.
Tip in at least 650g of green beans.
Let the TO do its stuff at 250C. Tip at cusp of second crack, or slightly into it.
Perfect results.
Burping is only needed for SHB varieties. Once at first crack, and again, 2 minutes later. I only do this for Kenyans, Yemen and Costa Rican beans. All others including blends are left alone.
The trick is to work out the capacity of your roaster, and adjust your technique accordingly.
Playing around with temps is a waste of time.
I followed KK's advice and have had great success. The only bad roasts were due to me becoming distracted and not ending the roast earlier. Even then, the roast was very good, just with some roast flavours becoming prominant, but no ashy taste.
KISS is always the best approach.

[readeral]

Don't give in. You will hit on a system that works for your taste, and once you have it, then you will be set.

Haha Shano, don't worry, I have absolutely no intention of giving in! Given I've nailed a few roasts, I know my built is capable so it's just a case (as you say) of getting the operator comfortable on a repeatable approach

I think with a KKTO Roaster, even though it's not absolutely necessary, consistent roasts (and therefore results in the cup) benefit from preheating such that the internal temp is between 130C-150C and stable before you drop the beans in.
...
A lot of people, of course, choose to go the simple path and use the KKTO as a set and forget kind of roaster, which it can do quite well; some of nicest results in the cup I have enjoyed, have been from a KKTO used in this way. All in all, I think the KKTO offers the best of both worlds, depending on how far you want to get into coffee roasting at home.

I think you're right here Mal. My best roasts have had a fairly high preheat (150-200 degrees) but I stopped preheating that high to try and avoid the tipping I was getting. But now I think about it, it was only the overly sensitive brazil green I had that was tipping with a preheat... possibly by lowering my preheat is causing more trouble than it solved.

I was thinking last night that possibly the element-style TO (remarkably hard to get now! Found one at JB-HiFi for more than I was willing to spend) is more desirable, despite their lag in responsiveness, given that the element remains hot while it's not receiving current. The glass halogen element can cool down almost instantaneously, so relying on circulating existing heat in the system - making paramount the importance of the pre-heat! I know this because the fluctuations I'm getting on my bean temp probe (one of Andy's, its definitely accurate - I test it often) can be pretty wild. So I think you're right on the dead-band comment too - will try a different model TO in the future.

A significant factor in my failed roast last night was that I tried roasting in Tasmania, not NSW, and my outdoor temperature dropped 10 degrees across the 20 minute roast. Learned my lesson - roast in the mid-morning/early-afternoon when in the south :P

I know a fair amount of roasting theory for a rookie, I have a bunch of friends that roast commercially and we talk about it often. Also, the internet is a wonderful place, and I _think_ I know enough to filter out the rubbish. Obviously the problem is that I need to better learn my roaster to apply that theory - and what I'm just not going to be able to achieve with it - and also how it responds to environmental changes. One can learn to make coffee quickly, as you're able to make 2-3 a day. Roasting takes a lot more time unless you're perfectly willing to roast up 5kg of beans that you'll likely not be able to drink.

I'm definitely not a set and forget fellow - I'm keen to roast to the benefit of getting the most from a bean, just need to work out how best to control this beast! So I think I'll return to my 175 degree 20 minute preheat, which usually gives me a turning point of around 60, and this will also reduce the number of step ups I'll need to take to increase my temperature across the roast - which will hopefully be a lot more consistent for me.

[bcspark]

I have a modded KKTO using a Steinel HG2300 heat gun fitted to a stainless steel top,shown in previous thread. By using 66% of available cyclonic airflow my main roast is 625grm of greens from ambient ,with full heat the roast takes 15-17 minutes to complete to CS9 @224deg.With my setup I have completed 1125 grm roast in the KKTO.My suggestion to you is to increase the batch size and let the beans roast them selves.Green beans will only use the heat they need to roast as Koffee Kosmo and I have agreed upon.

[Dimal]

I think with a KKTO Roaster, even though it's not absolutely necessary, consistent roasts (and therefore results in the cup) benefit from preheating such that the internal temp is between 130C-150C and stable before you drop the beans in.

A significant portion of the roasting in a KKTO is achieved by conduction with the sides and bottom of the vessel as well as convection and radiation from the TO itself. You're basically looking for a Turning Point of between 60-80C, so adjusting the batch mass and the TO heat setting may need to be juggled to get this.

As mentioned at the beginning, there's no need to go to these lengths but it will help in getting full roast development of the bean, and consistency in the cup.

A lot of people, of course, choose to go the simple path and use the KKTO as a set and forget kind of roaster, which it can do quite well; some of nicest results in the cup I have enjoyed, have been from a KKTO used in this way. All in all, I think the KKTO offers the best of both worlds, depending on how far you want to get into coffee roasting at home.

Some TOs seem to have a wide dead-band temperature controller and it seems that you may have 'lucked' on to one of those "readeral", unfortunately. I do know of a few KKTO users out there who have modified their TOs with a better type of controller but can't remember the details. Maybe one or more of them will chime in with some advice....

Mal.

[Shano592]

I have only done the one roast in mine so far, and it was about 400g.
I think the roast time was around 20 minutes, but I didn't really time it. I just watched it until it hit the right colour for me. I also didn't preheat it, but let it heat up from ambient with the beans.
2 days later, and the beans smell superb!
Don't give in. You will hit on a system that works for your taste, and once you have it, then you will be set.

[readeral]

Well as much as I might have a fancy looking KKTO, I absolutely haven't tamed the beast yet.

I'm feel like a total rookie, and without someone much more experienced roasting beside me and giving me feedback, it's definitely a frustrating experience. I think out of all my roasts, there has only been two that I've been totally happy with (ironaically my first two listed in this thread!), and some that have been 'fine'. I drink (almost) everything I roast though. The only exception was an especially old and dry brazil that I tried to roast I threw out cause it really wasn't suitable for roasting in the end.

Part of the trouble I think I'm having is because the turbo oven is just so sensitive to change, being fan forced AND a halogen element, that the pulsing of the element makes the temperatures hard to control. Preheating properly should help me mitigate this issue, but I don't feel like I've found the right pre-heat temperature yet.

It's also evidently remarkably hot at times I think. I'll end up with underdeveloped roasts that seem plenty dark enough - and sometimes also quite uneven, which is even worse. I think I need to start quite gentle, and then ramp up, and not be too scared to let the roasts exceed 20 minutes.

(The other thing I think that is impacting my roast is the spring that I added. I'll be removing that soon, because I suspect it is still pushing beans around a little bit, not helping with the unevenness)

I've been consistently trying to roast 600g - I'll be dropping down to 450 or 500g with my next efforts I think, to see if I can master the lower weights before trying to increase again. Any insight y'all can offer me (especially you Nick!) would be great!