Coretto cover project

[Steve82]

That sounds really familiar :-)
Having just played around with a popper for fun, I was reminded how different the results from an open/closed style of roasting are. The popper ( when I managed to stretch it out on a cold day), gave nice results, but ones that were much brighter & lighter than I'm used to.
I think that taste depth from the closed system has a lot to do with all the enclosed radiant heat in the pan (much closer to that of a commercial drum). Rather than just hot air blowing around the outside of the beans, it generates lots of radiant heat which sinks deep into the bean, giving a much gentler, deeper roast. Like searing your steak on the BBQ then dropping it in the oven for the heat to really get inside.
I certainly never had the deep chocolate results I can get now from my old setup. I've had some cracking results from a pre-blend mix of 150g Sulawesi and 200g Eth Sidamo … mmmmmmm … chocolate! :-)

Totally agree with this.

I had exactly the same thought about the steak literally 2 days ago. I am not using a data logger, my heat gun is 2000W with 2 settings.
My uncovered roasts, the gun had to be on the high setting and to my mind and taste it was sealing the outside of the bean prior to any heat getting inside the bean. Results where always brighter / lighter flavours which worked well for filter AP and cold brewing. However even going into second crack i was not pleased with the espresso shots, not much depth to the flavour, blonding quickly.

Now i am just using an old small pizza tray with a rock on it, to mostly cover the BM. The circle leaves a spot for the heat gun nozzle and another small opening on the pother side where steam / smoke / chaff escapes.
I can now run on the low heat setting for 7mins, gives a really nice even look early on and i can see / smell there is more heat getting into the beans. I then move the tray to about half covering and switch to full heat which gives me rolling FC around 10.30.
I then drop the HG back to low and cover up BM again and cruise for 3min, switch back to high and take the cover off altogether which results in start of SC around 1.30 later.

Results for espresso are just so much better i am very happy and so are my family (i am now roasting for them)
Deeper richer red / brown colour, loads of crema and the shot does not blonde nearly as quickly.
Flavours are much stronger and smoother and lasting = i can taste my coffee long after i have finished it.

Definitely am an advocate for covering the coretto!

[DesigningByCoffee]

Hi Steve
That's really interesting - you've got a totally different technique with the fixed gun & lid shuffle - but the resulting profile would be quite similar I'd think -v. similar times!
My setup is fully covered the whole time ( I don't see the beans till they hit the cooler) but I warm gently (180deg on the gun) for 3mins till 60deg on the DMM, then slowly ramp a couple of times up to 1C (360@60-DMM, 410@130-DMM, 460@160-DMM) then back off again the same amounts (410@195-DMM(1c) then 360@210-DMM) till just before 2C (about 223-DMM).

That gentle warm then climb to 1C seems to work a treat - and much less tipping & divots too ;-)

[Steve82]

Hi Steve
That's really interesting - you've got a totally different technique with the fixed gun & lid shuffle - but the resulting profile would be quite similar I'd think -v. similar times!
My setup is fully covered the whole time ( I don't see the beans till they hit the cooler) but I warm gently (180deg on the gun) for 3mins till 60deg on the DMM, then slowly ramp a couple of times up to 1C (360@60-DMM, 410@130-DMM, 460@160-DMM) then back off again the same amounts (410@195-DMM(1c) then 360@210-DMM) till just before 2C (about 223-DMM).

That gentle warm then climb to 1C seems to work a treat - and much less tipping & divots too ;-)

Yeah the perfectionist in me would dearly love to get temp probe / data logger, full cover and try profile by temp alone.
But alas it needs to stay a cheap ghetto hobby for now, the only thing i have purchased for roasting is the heat gun, Exceed for $40.

I should note that i stick to the same batch size of 450g green each time, if this changes, this technique would need to be tweaked slightly.
Its all about sight, sound, smell which i have to say i quite enjoy at the moment, all the way through to the cup.

I also get no tipping or divots now, early days with popper ect it was crater city!

Its just great to get it to stage where other people are wanting it, which gives me more opportunity to practice the art.
And im turning out 1kg of roasted beans for around $16 / KG, how good is home roasting!

[DesigningByCoffee]

And im turning out 1kg of roasted beans for around $16 / KG, how good is home roasting!

Hearing you there!

[artman]

I will have to start playing around with insulation a bit etc. My ozito finally gave up the ghost (defrosting the freezer!!), it still works but only develops heat about as good as a hair drier. Contemplating upgrading to a digital gun, for now borrowing a basic one from my brother while I think about it a bit more...

Cheers

[saoye]

I will have to start playing around with insulation a bit etc. My ozito finally gave up the ghost (defrosting the freezer!!), it still works but only develops heat about as good as a hair drier. Contemplating upgrading to a digital gun, for now borrowing a basic one from my brother while I think about it a bit more...

Cheers

Well, I'd justify the purchase as "it's for the home and the last one broke not because of roasting so I need something more reliable" incidentally aren't the Ozitos 3 year replacement warranty? How long have you had it? Would be interesting to see if they really do honour it.

[artman]

I just did a roast with the borrowed Ryobi HG. Has what looks like digital control (no readout, just a few LEDs), made it much simpler than raising HG etc, can see where the benefit of the nice Bosch guns could be handy.

The Ozito actually stopped working a few months back, took it to Bunnings, the guy was about to give me a replacement but then checked the receipt, and the warranty just ran out. I didnt realise I missed the warranty period by a few days. I tried it again a few days later and it was fine!? It finally gave up the ghost recently. So yes, it does look like they honour their warranty without questions (he didnt even try it to see what was wrong), and it has done a heap of work roasting beans in its life, so for the price, great performance I reckon!

Cheers

[saoye]

I just did a roast with the borrowed Ryobi HG. Has what looks like digital control (no readout, just a few LEDs), made it much simpler than raising HG etc, can see where the benefit of the nice Bosch guns could be handy.

The Ozito actually stopped working a few months back, took it to Bunnings, the guy was about to give me a replacement but then checked the receipt, and the warranty just ran out. I didnt realise I missed the warranty period by a few days. I tried it again a few days later and it was fine!? It finally gave up the ghost recently. So yes, it does look like they honour their warranty without questions (he didnt even try it to see what was wrong), and it has done a heap of work roasting beans in its life, so for the price, great performance I reckon!

Cheers

Well I have tried a few roasts with the cover and it's becoming more evident to me the need to have accurate heat control since there is nothing else in the system that will allow me to alter the temperature inside the pan. I tried anticipating lag for the Ozito but my conclusion is that the control is not sensitive enough to allow for a real controlled roast. The issue is the heat control on occassions seems not to activate with small twists and when waiting for the temp to raise and nothing happens (in fact it's falling) I do a tiny adjustment and the temperature then shoots skywards according to the data logger. I'm still able to roast but it is quite a task to constantly adjust the temp on the ozito.

I'm wondering really how accurate and sensitive is the Bosch 630? Keeping an eye out on any second hand available.

[DesigningByCoffee]

Hi Saoye
The Bosch is like a metronome!
But you might be able to do so more experimenting with your setup first. If you check out this post…

http://coffeesnobs.com.au/home-roast...profiling.html

… you'll see that I logged the heat getting into the pan just inside the inlet port for my Bosch gun at the full range of gun settings, and for every 10deg rise on the gun (the min. digital steps available) I got an extra 7.5 degree temp into the pan - accurately right through the gun range! That's pretty precise :-)
I suspect that the cheaper adjustable guns might be a bit hit an miss with their simple rotary dial - but I'd be interested to see hard proof. No-one has taken up the challenge yet of profiling their current setup using the good ole DMM we already have lying around - but I reckon if you tried it with your current gun you'd see what it is doing when you change temps. Just do a dry pan run with the ozito - can't hurt!

But I agree - with a covered system you need to be able to accurately adjust the temps pretty accurately - maybe adjusting gun height with an extension nozzle could work?
Matt

[saoye]

Hi Saoye
The Bosch is like a metronome!
But you might be able to do so more experimenting with your setup first. If you check out this post…

http://coffeesnobs.com.au/home-roast...profiling.html

… you'll see that I logged the heat getting into the pan just inside the inlet port for my Bosch gun at the full range of gun settings, and for every 10deg rise on the gun (the min. digital steps available) I got an extra 7.5 degree temp into the pan - accurately right through the gun range! That's pretty precise :-)
I suspect that the cheaper adjustable guns might be a bit hit an miss with their simple rotary dial - but I'd be interested to see hard proof. No-one has taken up the challenge yet of profiling their current setup using the good ole DMM we already have lying around - but I reckon if you tried it with your current gun you'd see what it is doing when you change temps. Just do a dry pan run with the ozito - can't hurt!

But I agree - with a covered system you need to be able to accurately adjust the temps pretty accurately - maybe adjusting gun height with an extension nozzle could work?
Matt

Hi matt, the ozito does not have actual temp settings as much as dial position from low to high going clockwise. I'll see what I can do though.

[saoye]

Ok just did it. Here's what it looks like without bread maker on. Surprising. Interesting to note becomes somewhat sensitive as we get to the warmer setting which can account for my spikes. At 6 oclock I have only turned the dial to the half way point. How do I attach an exel file for the settings I made?

[artman]

I think trying to adjust the temp of a gun like the Ozito is a bit hit and miss, the temp adjustment appears to be a simple rheostat, and I have found it all over the place. So I just kept mine on full and adjusted the height of the gun to adjust temperature.

Cheers

[DesigningByCoffee]

Wow - that's really interesting!
Appears like what seems like a smooth rotary dial (kind of expecting a light dimmer?) this gun unit actually has a few very specific contacts within the dial. No wonder smooth temp control can be an issue!

[Beanz.]

It appears that the temperature control is a bimetallic system, bimetallic controls are either on or off and that is why you see the spike in heat input as it switches the element on and off. When it gets to the set temperature the contact opens and it switches off the element.

Wikipedia can explain it better than I can:

"Thermostats See also: Tipping points and 'popping disc' bimetal thermostats
In the regulation of heating and cooling, thermostats that operate over a wide range of temperatures are used. In these, one end of the bimetal strip is mechanically fixed and attached to an electrical power source, while the other (moving) end carries an electrical contact. In adjustable thermostats another contact is positioned with a regulating knob or lever. The position so set controls the regulated temperature, called the set point."

The low cost Heat Guns will have cheaper control systems, I would expect the higher cost guns may have better control systems. The other side effect of the bimetallic type is that it can introduce electrical pulses or spikes into the temperature monitoring systems which can create problems if you are trying to graph the process.

I use a cheap Aldi heat gun but use an old theatre lighting dimmer to regulate the temperature, it is capable of 10 Amps which is more than adequate and I have very fine control via a slider. The one thing you need to be careful of with the dimmer is that you do not run it too low as you run the risk of damaging the fan motor, I have found that at the start of the roast the lowest setting I use allows adequate fan speed but this may vary depending on the brand of HG. The Aldi $19 gun has done 100+ roasts with no problems.

[saoye]

I have an excel file that I recorded the readings which correlates to the graph. Dunno how to attach an exel file but here it is in pdf. Anyway, I started my reading at zero or 12 oclock meaning heat is essentially off. Interesting to note at zero it is outputting heat. So at each spike is when I turned the dial once I think the temperature has stabilised.

Settings.pdf