Phil, from what I've picked up over the last couple of weeks since having a go at roasting in my popper, it seems these things tend to roast slightly faster than the big commercial machines. But the good news is, you can roast fantastic coffee, especially by keeping in touch with folks on this forum and others.
Here's what I've found out about my little machine, which is the Breville Crazy popper: I need to roast 75-90 gms of green beans in order to get to the second crack. Because less than this, tends to permit a greater airflow and therefore a lower temp. However, this may just be because its still relatively cold here and summer time may be quite different.
I've been told to allow the machine to cool down in between batches, so I place it in a drafty position for 10-15 mins.
Ambient air temp plays a small part in increasing or decreasing roast times.
I am moving away from actually timing my roast and now I watch and listen for the first or second crack to let me know how the roast is progressing. This is very easy to do, you really can't go wrong.
Corn poppers work very well but the life expectancy is probably reduced when compared to using the thing for popping corn.
I worked out I need only to roast 3 kilos of beans in order for the popper to pay for itself with the savings I get from buying green beans.
I leave my beans for 4 days before using them. They are great. Less than this and I can taste the CO2 or what ever it is. It tastes like a kind of sharp acid and is not nice.
There is a lot of information out there regarding different origins and roasting times etc. I would suggest, don't get too worried about all this, its pretty hard to botch anything IMO.
I started with a little good info about which were quality beans to buy, then began my own experimentation with roast times. I have not had any bad coffee yet :wink:
I have gotten friendly with a local roaster who is very open and helpful.
There is much reading to be had by googling " Roasting Coffee beans in a corn popper".
Have fun.
ArabB.
