Another Corretto Build

[WhatEverBeansNecessary]

Morning all.

Have been thinking a bit about the temperature probe and why it seemed that my FC/SC temps were well above what is the accepted standard for arabica beans at 196 deg C.

There is three different aspects that I think will be affecting why my reading is significantly above 196:
1. I missed the very start of FC and where I registered FC was actually some degrees cooler, but couldn't hear the first snaps and the temperature kept rising
2. The temp probe isn't truly reflecting the bean temp but a hybrid of the bean temp and air temp
3. The calibration is a bit out on the temp probe

I think all 3 are partly true to some extent, but 1 & 2 are hard to verify - so I decided to do and experiment to verify #3.

I boiled a pot of water and kept it at a rolling boil on the stove and inserted the temp probe. I then let it sit in the water for a good 10 mins making sure the probe didn't touch the bottom, only the water itself.
Results - well it was pretty clear. The probe registered 103.8 (there was a little movement back and forth). Given water boils at 100 degrees C at sea level and I'm only 150M from the beach I'd think the calibration is indeed out a little at 100 degrees C, perhaps 3-4 degrees C.

What this means for my roast:
I recorded FC at around 204 Degrees C (from memory, but should check my actual log!) - so even taking this into account I'm still 4 degrees or so out. Which means more than likely I missed the start of FC and the temp probe doesn't 100% reflect bean temperature, but both bean and air temperature.

[Dimal]

If you're using a heatsnob, Andy has had these designed so that they are reporting accurate temperatures around the range of most interest to we roasters, ie before 1st-Crack and through to 2nd-Crack. Output from t/couples are not linear so it is always important to have instrumentation calibrated to that part of the output curve that is of interest...

Mal.

[WhatEverBeansNecessary]

Hi Mal, yes certainly using the heatsnob and as Yelta mentioned below I think chasing certain temperatures isn't important, so long as it's repeatable. Being only the 2nd roast I can't quite comment yet!

[Yelta]

Morning all.

Have been thinking a bit about the temperature probe and why it seemed that my FC/SC temps were well above what is the accepted standard for arabica beans at 196 deg C.

There is three different aspects that I think will be affecting why my reading is significantly above 196:
1. I missed the very start of FC and where I registered FC was actually some degrees cooler, but couldn't hear the first snaps and the temperature kept rising
2. The temp probe isn't truly reflecting the bean temp but a hybrid of the bean temp and air temp
3. The calibration is a bit out on the temp probe

I think all 3 are partly true to some extent, but 1 & 2 are hard to verify - so I decided to do and experiment to verify #3.

I boiled a pot of water and kept it at a rolling boil on the stove and inserted the temp probe. I then let it sit in the water for a good 10 mins making sure the probe didn't touch the bottom, only the water itself.
Results - well it was pretty clear. The probe registered 103.8 (there was a little movement back and forth). Given water boils at 100 degrees C at sea level and I'm only 150M from the beach I'd think the calibration is indeed out a little at 100 degrees C, perhaps 3-4 degrees C.

What this means for my roast:
I recorded FC at around 204 Degrees C (from memory, but should check my actual log!) - so even taking this into account I'm still 4 degrees or so out. Which means more than likely I missed the start of FC and the temp probe doesn't 100% reflect bean temperature, but both bean and air temperature.

Morning WBN,

I wouldn't get too hung up on precise temperature, these temp measuring devices are not calibrated scientific instruments, the important thing is repeatability, once you become accustomed to your particular set up you will get to know what to expect and when to expect it.

Provided the probe is in the centre of the beans it should come up with reliable readings each and every roast.

As far as first crack is concerned I find it very easy to hear {do you have a hearing problem,? I do) or is the noise from your heat gun or bread maker drowning it out? I use a DMM with a temperature probe inserted pretty well into the centre of the bean mass, I find FC always occurs at around 200°C plus or minus a couple of degree's, and goes on for a minute or so then tails off.

I stop most of my roasts @ around 225°C just prior to second crack, SC as a matter of interest is much more subtle than FC and can be difficult to hear.

I did PM you my phone number, if you would like to discuss further I'm happy to assist, can perhaps discuss in more detail than we can in writing.

[WhatEverBeansNecessary]

Morning Yelta,
No hearing problems that I am aware of - but there is always a possibility!

I think the noise of the HG is drowning out the FC, but could also be these beans are a more subtle FC than some which have the real distinctive snap. Best to get a few more roasts under the belt and just see if on this occasion I missed it.
Might also have a play with the lower fan speed on the gun and see if that makes less noise as well as on another post someone mentioned that it dries the beans out too much (not sure if that's the reality or not).

[Yelta]

Not familiar with the Ozito heat gun and its noise level, I use a Bosch and run it on blower speed 2, it has 3 settings, it's not very loud, so FC is easy enough to hear over it.

[WhatEverBeansNecessary]

Completed another roast last night with a bigger batch 550g. Results yet to be determined in the cup, but dropped them quite a bit cooler in an attempt to get a lighter roast.

FC at the 14.5 minute mark but in an attempt to not let the roast get away I dropped the heat a little too much which probably led to a bit much time between FC and cooling, approx 6.5 minutes.

Interestingly I did notice a much clearer snap of FC at about 198 degrees - so perhaps the larger batch volume means I am reading a 'truer' bean temp. Cooled the batch at the 210 degree mark but the result was still a darker roast (maybe a CS9?).
There was also a lot of noise with the temperature probe bouncing the temp up and down which made the roast more challenging.

The larger batch size also highlighted the need for a better bean cooling setup which will be on the cards before the next large batch.

[Pollperth]

I have the same heat gun in my set-up, and the dial is really sketchy for repeatable results. My solution was the plug the gun in via a watt-meter so I can set it to exactly the same wattage each time (like gas pressure on a traditional drum roaster).

Not too pricey, and can be used to check the consumption of other household appliances when not doing coffee duty

[zuroy]

How do you currently cool it? I currently have a colander (thousands of holes all over it) and put it on top of my fan (laid flat on the ground). Stir it with a wooden stick for a bit over a minute and it’s mostly room temperature given it’s winter now.

Hope that gives inspiration or let me know if there’s an even faster way.

[WhatEverBeansNecessary]

This was the first iteration but have since changed the design slightly. But basic design is a bit plastic bucket with a bathroom fan placed underneath. I then cut out 4 large holes at the bottom to let air in (and poke the cord through). Total cost was $32 = $17 for the fan, $5 for the bucket, $10 for the colander.

First iteration I had the colander placed about 10cm above the fan, but found the flow of air mostly went around the bucket rather than through the holes and coffee sitting in the colander.

Now I have got a larger colander (Ikea has a perfect one for $10) which has more holes but smaller. I have cut a few notches into the bucket itself so that the colanders handles fit snugly in the notches and the lid can snap on to the top with similar notches on the lid.I then cut out a hole slightly smaller than the diameter of the colander.

This way the air is forced through the holes and unable to escape around the outside of the colander/bucket. This way works much better and cools 500g of beans in about 2 minutes to a cool enough temperature to handle from more like 4 or 5 minutes. Small change in times but I figure for larger batches it will be even more efficient. I also stir the beans with a spoon to aid the cooling and it also helps remove excess chaff.

Will try get some photos during the next roast of the second iteration.

[WhatEverBeansNecessary]

Morning all,

Update on this build!

I was roasting over the weekend and disaster struck! Set the bread maker on the dough cycle as per normal. Wait the initial intermittent paddle rotating before it goes into constant rotation (6 mins from memory). Loaded the beans, got the heat gun going. About 4 mins into the roast the bread maker stopped!
Turned the gun off immediately and carefully removed the burnt beans and those around which were clearly more roasted than the others. Normally I would chuck the whole roast out, but this was my last lot of greens and had the option of either buying some elsewhere to keep going until my next order came through or salvage and re-roast. Decided I would re-roast knowing full well they won't be great.
Got out the old Behmor and finished off the roast and had a brew this morning with them. Surprisingly they are 'okay' - very flat and a bit baked, but not horrible. Luckily the beans were only just starting to yellow so hand't gotten too deep in the roast,

However I retested the bread maker and it would turn on and spin but would shut off after a minute or two with an error. Couldn't find any error codes online for the machine so the bread maker probably overheated and shorted/burnt out something or some other similar issue. Decided I would give it a go rewiring the thing as it was either that or get another bread maker.

WARNING: Do not try rewire any household appliance unless you know what you are doing. 240V can kill!

Having some electrical experience decided it couldn't be too hard. Spent a bit of time looking at this forum and a couple others to get a general idea of what I needed to do. Basically I only had to wire the existing power cable to the motor with the start capacitor in the circuit too - would just depend on the existing wiring where I needed wire the power cable in.
Removed all the circuitry and took a bunch of photos of the circuit as it had named many of the wires conveniently.
Used some contactors to wire the cables all up the right way (super easy) and gave it a test. Success!
Now it spins constantly without the need for waiting 6 minutes for the paddle to stir constantly.

Also added a little off cut of the fire blanket between the housing for the bread tin and where the circuit would normally be (sandwiched between the housing and a secondary aluminium plate/bracket) just to stop some of the heat messing with the wiring.

And as I wrote this my delivery of Burundi and Colombian Volcan got delivered - ordered Monday, arrived Wednesday - near on 48 hours from Geelong to Adelaide. Thanks Andy, service is unreal.

[Yelta]

"Success! Now it spins constantly without the need for waiting 6 minutes for the paddle to stir constantly."
Good move WBN, certainly simplifies the roasting process.
Pleased to hear the roast wasn't a total loss.

[gpang]

Good job. Added to my project list.