I am new to roasting so have been reading with interest what others have had to say.
It appears as a general rule of thumb that the time to first crack is 8 to 12 minutes
But no mention of batch size in most cases.
Wouldn't batch size affect the time to first crack or does the above cover all common batch sizes?
thank you

Many factors go into the equation, volume or mass being one of them:

Voltage at the wall
Batch size
Bean
Heat application
Appliance/device used

With the Behmor, suggest you use 12 oz as a start point and see how that works.

B|Java

Batch size is dependent on the roaster in question, that is why it is not mentioned. With my Behmor I had dropped to 5-6 ozs for hard bean/high grown coffee, yet with my Ambex I can run full charge weight of 2 Kilo and hit my marks.

To those that replied Thank You

A few of the contestents in the roast competition used Behmor's and provided some comments on the batch size they settled on. I found that interesting reading.

Short answer: yes.

Use the 8-12 minute comment as a guideline. If your batches are of sufficient weight that you don't get to 1C before 12 minutes, lower the batch size. As others on the post have said, it's roaster dependent - your rig has to pump out enough heat.

For my roaster, the sweet spot is around 400g/14oz. I can go lower with control, but don't feel comfortable going heavier, as I can't pump enough heat into the chamber to reach my desired time target for 1C.

It also matters how hot the drum gets. Time is important but you don't want to get the drum at for example +900F. So if you use a larger than normal batch, you may increase the power-temperature to keep the same time. But you could get a burnt flavor. This can also happen when room temperature is cold (winter) and use higher than normal power. Some beans are better than others at high drum temps.

Cheers

oconee wrote:A few of the contestents in the roast competition used Behmor's and provided some comments on the batch size they settled on. I found that interesting reading.

Can you provide the location of the article you mention

Arpi wrote:It also matters how hot the drum gets. Time is important but you don't want to get the drum at for example +900F. So if you use a larger than normal batch, you may increase the power-temperature to keep the same time. But you could get a burnt flavor. This can also happen when room temperature is cold (winter) and use higher than normal power. Some beans are better than others at high drum temps.

Cheers

Not a factor with a Behmor, the main issue is that it has a mesh drum and even trying to pre-heat the unit is tricky. The units temp sensor and computer logic makes for difficult heat management, and most times up to 1C is too low and slow, then too fast after 1C. I worked with mine in completely stock form, but many modded the unit to take over control of the heating elements/temp sensor/fan; by-passing the logic board. It still turns out to be difficult to control because of the direct heat on the beans from the infra-red elements.

oconee wrote:A few of the contestents in the roast competition used Behmor's and provided some comments on the batch size they settled on. I found that interesting reading.

In my Behmor, I normally dose 250 - 300 grams for 1# roast settings. I tend toward 250 gram batches for coffees that I'm trying to emphasize brightness and fruit on. I also recently roasted up four Dominican Republic coffee samples from Theta Ridge and used ~180 gram doses on 1/2# P3 A roast profiles which I think worked pretty well. I'd culled 200 gram samples and roasted the nice beans that remained.

I do pre-heat the Behmor for two minutes with the chaff tray installed (and drum out, waiting with loaded greens) which results in a drop-in temp of about 200 degrees F. The ET in the roaster hits upwards of 280, but when I shut down the roaster, quickly open the door and pull out the old-style chaff tray with my Ove Gloved hands and put in the drum and start up with my desired profile, it's dropped down. Any longer than two minutes (it varies depending on the particular Behmor) and you risk being unable to re-start the roaster due to the control circuit preventing a restart over a certain temperature.

With the Behmor, there is a gradual ramp up to temp that corresponds to the drying phase of the beans. I feel you want to tweak your load size so that that ramp works well for the drying phase and then I compensate for the roaster's tendency to roll from first crack right into second by cracking the door a bit (sometimes propping it open with a metal tweezers I use for culling beans) while monitoring the ET temperature with a Thermocouple and RoasterThing software.

After reading the Scandinavian style thread, I've begun to slow the roast right when the greens hit full yellow, well before first crack, to emphasize the sweetness and then when first crack hits I'll drop the temp even further and stretch out first. The more gentle P3 profile with the DR beans seemed to match the lower temp during full yellow pretty well with the batch size I picked. It's also more appropriate for a lower-grown island bean.