Hopefully I'm not the only person on this forum who has more questions (rather than fewer) as I spend more time thinking about coffee and (especially) roasting.

I've been looking at Joper roasters recently as well as sneaking a peak at Giesens. I have noticed that the 1 kg and 3 kg Jopers have single wall cast iron drums whereas 5 kg and larger have dual wall drums. The Giesen W6 has a dual wall drum but I'm not sure what the drum configuration for the W1 is.

Anyone have thoughts about single versus dual wall drums especially given different roaster sizes?

Thanks,
T

Drums with double walls utilizes the air between the walls as insulator to prevent local over heating, i.e. scorching.

As the number of roasting progresses, more and more energy is stored in the drum. The double wall improves consistency by reducing transfer of energy to the inner drum. For example, in the double walled drum roaster, the 2nd roast will have similar profile as as the 10th roast, given similar air flow, gas setting, drum rotation, etc.

All this is based on a single pass atmospheric roaster. If air is recirculated, the partial oxygen concentration decreases, the profile will again be different.

Thanks Henry,

Apart from longer preheating I then assume that double wall should always be preferable to single wall. For the Joper roasters then I assume that single wall for the smaller roasters is a result of production cost minimisation?

T

Generally, double walled roasters are more consistent batch to batch; this is especially important in commercial settings.

Think air bake cookie sheet. Nice brown cookies with no scorched bottoms.