This was my third attempt at roasting coffee beans using the Corretto method.

Heat gun was too far away and the heat gain wasn’t fast enough (see temperature log at end of post)

Had a few problems with the distance that the heat gun was away from the mixing bowl. Had to tilt the tripod too much to get it close enough and ending up holding the tripod for 20mins.

250mm fan in base blows a lot of air up through hot beans

The new bean cooler in action – worked well except for problem with the size of the holes in the strainer. Apart from a few beans lost through the large holes – it was a very effective cooler – the 250mm fan moves a lot of air and it’s intake was virtually unimpeded.

The holes in the bean cooler proved to be too large for some of the smaller sized beans

Some of the smaller beans fell through the strainer. I’ll have to add a stainless steel mesh insert to avoid this problem. Only about 10 little beans made it through though.

My son, Pip, enjoying the aroma of a fresh bean roast

Indoctrinating my three year old son in the art of home roasting.

Pip assisting me with the roasting process – the goggles and air muffs where his idea

He’s a bit of a safety nut. Come to think of it… I should’ve worn glasses and maybe gloves too – just incase things went pear shaped.

The tripod proved too inflexible for mounting the heat gun

The full rig in action.

My third attempt at roasting coffee… heat was a bit too low to start with.

How not to postion the heat gun while stirring the beans and watching the time and temperature

My first roast. I couldn’t wait to find and build my bread maker based Corretto roaster – so just got a pot and started stirring. Didn’t go well – it was very hard to hold the pan still, keep the temperature sensor in the bean mass, stir and hold the heat gun.

I got to first crack on track but never made second crack by 20mins so stopped. Beans where a lighter roast colour but still made an OK shot once they’d matured for a few days.

Cooling my beans the Australian way

Not having yet made my bean cooler – I just poured them onto a cool marble benchtop and blew a fan on them. Shaping them into the map of Australia seemed to be the coolest configuration.

Using a Fluke 289 DMM with cheap thermocoupler to measure and plot the roasting profile temperature

It’s obvious from this profile that my ability to maintain a steady temperature was very poor using the wooden spoon mixing technique.

Ian holding the heat gun

Today I tested out my modified bread maker for the first time. Having removed the over-temperature fuse from the mixer and the control board – it works beautifully – turn it on an it goes round and round.

My mate Ian was the “drill press stand holder” for this batch. I still haven’t managed to find an old one or fashioned something out of wood. I’m considering the closed Corretto method next so may make a metal cover for the unit with exhaust shoot for the chaff.

Monitoring the roasting time and bean mass temperature

Keeping a track on temperature and time isn’t so easy. There was a minute or two lag between changing the heat gun’s position and seeing that change reflected in the bean mass temperature. I’m leaning towards insulating the outside of the mixing bowl to stabilize the temperature better.

The new auto mixer in action

Bean colour was much more even than with hand mixing in my first effort. Only problem I had was that the mixing bowl had expanded and couldn’t be pulled free of the unit when the time came to empty the beans. I ending up just tipping the whole unit upside down onto the stainless steel bench top.

Temperature plot of my second roast

I forgot to turn on the recording function till about 4-5 minutes in to the roast.

Today I ripped apart an old bread maker and turned it into one of the components of a Coretto Method coffee roaster.

Here’s how

Looking down into bread maker with mixing bowl and surround removed

Since you want the bread maker’s beater to rotate continuously, not intermittently like most bread makers do – then you’ll need to somehow override the program settings. A more permanent method – and one only undertaken by someone who’s competent with repairing electrical appliances – is to remove the control board and hard wire the motor to the power switch.

Control board removed from bread maker

The small component in the front is the temperature cutout that was attached to the side of the mixer bowl. This too would’ve been a problem as it may have turned off the mixer when the beans got hot.

Temperature sensor in corner of mixing bowl – clear of the beater’s arm.

Drill a hole in the side of the bread maker in a slightly downward facing direction so that the vibration of the machine doesn’t cause the temperature sensor to rattle out. Best to place it near the bottom of the bowl in the corner – away from the mixer blade.

The head gun will eventually be more permanently mounted on a stand so that the height above the beans can be adjusted

Notice the temperature chart on the wall behind. You need to follow this closely while watching your stop watch – adjusting the heat gun’s temperature to maintain the profile. Best done while concentrating and not chatting to a new coffee friend.