Hottop tipping/scorching

[brendogs]

Hi there,

I just wanted to put it out there and see if anyone else is getting the same results as me.

As per title I've found lately that all my roasts have had signs of sometimes significant tipping. As I've been trying really hard to avoid it in the past few weeks I'm getting mixed results. I started lowering the drop temp ranging from 130C - 160C to see if I was going to get a different result. I've tried extending the roast and giving it a much more gentle rate of rise.

Today I dropped in at 150C with some Brazil Pulped Naturals using a charge weight of 160g to try and not over load it and I probably got my best results in regards to not so much tipping probably around 30% of the beans have signs of tipping (but this is more than enough to taint and ruin the cup). The profile today was basically 150C drop temp, extended the drying phase, had the airflow on from the middle of drying phase to the end of the roast to make sure there was sufficient airflow. I'm ejecting just before 2C.

I've tried extending the roast and trying to be more gentle on the RoR, 18-20min roast time.
I've tried to be a little more aggressive with higher airflow total 12-14min roast time.
I've tried both of these with higher drop temps of 180C down to 130C.

I have a feeling the beans are spending too much time on the drum and scorching, I am thinking of removing the drum and fabricating up some new stainless fins to try and replicate the Behmor style agitation fins which I think work great.

Any thoughts? Has anyone else encountered this problem.

[Col3]

Hi brendogs,

What machine are you using? Sorry just saw hottop in the subject. The rest of this is not very useful tgen eh. To give background I use an insulated corretto with cover and a bosch 'green' heat gun w/ digital input temp. Also I'm reasonably new to it all as only just ive cracked 15kgs (pun not intended ). My current charged weight is 500g.

I experienced a few tipping batches and found the biggest impact was air flow rate. I now leave it purely on 2 and just adjust the temp.

To check if it was the issue I have varied my charged temp between 100 and 209 degrees, tried higher input temps with lower air flow rate and ran initally fan 3 to 100 - 150C. Only thing that caused tipping for me was putting on fan 3.

Hope that helps.
Col

[chokkidog]

Brendogs, irrespective of your charge temp.....what is your turn temp?

p.s. Col.... as per thread title Brendogs is using a Hottop.

[brendogs]

Brendogs, irrespective of your charge temp.....what is your turn temp?

p.s. Col.... as per thread title Brendogs is using a Hottop.

My drop temp today was 140C and the turn temp was 70C at 1 min. These are taken from the BT where I do all my datalogging with the hottop.

Last week I tried a higher drop of 170C with an 80C turn at 1min. When I drop I turn the heat source down to 50% with the fan on half speed to try and steady the first rise so it doesn't gather too much momentum into the drying phase.

[chokkidog]

I'm not familiar with the Hottop..........but

Is it possible to try to aim for a turn temp as close to 60°C as possible?

Are you able to heat the roaster to (say) 180°C, turn heat and air off, then charge the drum as the temp drops through

160°C, turning heat and air back on about 5 seconds after the turn?

Playing around with this technique might be a starting point to achieving a suitable turn and to solve your issues.

It sort of reflects what I do in the HG5, same turn temp (60°C) but otherwise based on your temps.

[brendogs]

Yeah I can only try, because it's electric I need to anticipate techniques 2 or 3 steps before it happens. I'll see how it goes tonight and post the results but I think that could be achievable.

I guess doing this will flatten out the rising curve up to drying phase as well so I can have a tad more control over that. I'll give it a go.

At what times do you aim to hit the turn? I know the drums are completely different from the HG5 to the Hottop so it's hard to compare but it's good to know.

I know scorching is mostly caused at an overly hot drum, but when is tipping produced? Is it a mixture of aggressive heat rise and high drop temps? It's tough on the hottop because I can't actually sample beans during the roast and note down when I can see the start of tipping.

Thanks chokki

[chokkidog]

Tipping is caused by excessive drum surface temp at charge and / or too high a turn temp.

These events cause rapid, uneven drying especially at the germination end of the bean where sugars are concentrated.

The tipping marks don't actually show up until late in the roast when those areas roast to a higher level than the rest of the bean.

Scorching occurs later in the roast when there is too much heat after the onset of pyrolysis, or when

the sugars start to caramelise; theoretically at 183°C but will differ according to your own set up and conditions.

Facing, where the 'flat' surface of the bean scorches is generally caused by too much heat after 1st crack.

The ideas I suggested are only that......suggestions. Sometimes things can be learnt by doing something radical.

[brendogs]

Thanks for that chokki, I'll give it a go tonight and lower the drop and turn temps. I've researched it a hell of a lot and as I've been reading and reading I'm absorbing all this endless information.

I'm getting closer, the problem is that I think the Hottop is letting me down slightly. The drum doesn't have any fins so the agitation just isn't enough. The beans are spending far too much time on the drum walls so I'll try and work with these drop and turn temps we are talking about but my next project is going to be to remove the drum and add some fins. I've got a 1kg JYR TJ-067 that I'm fixing up and I was hoping that I could try and emulate roasts from the hottop onto that but I just don't think the environments are going to match and give me completely mixed results.

I'll try a couple roasts tonight and discuss my results.

[kwantfm]

I use a drum roaster similar to a Hottop and initially had lots of problems with tipping and scorching. I did two things that solved the issues. The first was to reduce charge temp... I charge at 160*C bean temp. The second was to paint the outer surface of the drum with kettle black. The increased emissivity of the setup and greater conduction allowed me to use less power through the roast.

[chokkidog]

Vigorous, constant agitation that keeps the integrity of the bean mass and doesn't spray beans in all directions will

go a long way to achieving the results you're after.

The Baby roaster also works better when modded with paddles.

[summercrema]

Brendogs, can you post the roasting profile ?

[TC]

....I was hoping that I could try and emulate roasts from the hottop onto that but I just don't think the environments are going to match and give me completely mixed results...

I have always said that a new roaster is somewhat like a new partner. What works for one may not necessarily suit the other. It's takes some getting to know you time.

Sacrifice some beans and you will learn what the bigger roaster requires to deliver your desired results. It's likely that even the seasoning roasts will help you learn.

Enjoy

[chokkidog]

Agreed, which is why I deleted a couple of details that are pertinent to my roaster, in my situation, with its unique ambience

dynamics which apply to the beans I roast and how I roast them.

This principle applies to everyone.

Brendogs....I'd worry less about the Hottop and get cracking on your new roaster; solving issues on the Hottop will add

to your experience but it is the experience and not the hard data that will help with the newy.

[brendogs]

Brendogs....I'd worry less about the Hottop and get cracking on your new roaster; solving issues on the Hottop will add

to your experience but it is the experience and not the hard data that will help with the newy.

I would love to chokki but I'm waiting for some part's, I purchased it fairly cheap because it had a blown solid state relay in it because one of the elements shorted. Just waiting on the replacement parts to come in from North Coffee. Once that is ready to go I'll start cranking it over.

I have always said that a new roaster is somewhat like a new partner. What works for one may not necessarily suit the other. It's takes some getting to know you time.

Does this mean that after the honeymoon period is over it will start contradicting me and telling me I'm always wrong?! I don't know if I'm game enough for this. Haha

Just about to load the beans in and try a lower and steady turn temp.

[brendogs]

So I've just given it a go, still got signs of tipping. I didn't quite get it down to 60C, more like 65C. It just didn't want to stop the momentum. Had a very steady rise up to drying phase raised the airflow and then let the roast go up to 1C with the airflow on. 1C developed for just over 1:30 then let it develop for another 1:30 post 1C and dumped. Some of the beans even have signs of facing as well.

I'm absolutely adamant that the lack of fins is causing this. The beans are basically rolling on the bottom of the drum, barely rising on the side of the drum unless there is a larger charge weight. I'm going to take it out and bring it to work to fit some fins. With a smaller charge weight the beans are spending even more time on the drum face than with a larger charge.

Rather annoyed that I've been wasting so many beans on this! Grrrrrr