capacity surprise with big beans

[dickcoffee]

I had a surprise yesterday when roasting a El Salvador Pacamara dry process  bean I got from Burman.  I always do 1 pound batches in my solid drum with no problems.  Typically I get 1st crack around 385.  With this bean --- I did 2 roasts to be sure, I didn't get 1st crack till 400 on both roasts.  The temperatures all along the way seemed out of kilter.  I couldn't seem to get enough heat. And, the j Tube was full of chaff.  Actually, the roast looks nice enough and smell great.  Maybe my lack of a developed palate will be to my advantage.  Anyhow, I would never do a 1 pound batch of dry process Pacamaras again.  They are huge, by the way. 

[edtbjon]

I don't think that the full pound charge was the problem. I recon that much of the cause for the problematic roast lies in the blocked exhaust pipe. Naturals in general produces much more chaff and if there's something in the pipe to block it up before even beginning this can happen. Been there - done that. ... even with the J-pipe, while the T-pipe is much more prone to block up.
The "late" 1Cs may indicate something too, but again, I usually get more reliable temp readings with larger charges. I.e the late 1Cs doesn't have to mean anything. The only thing with naturals which I usually do is to try to stay in the drying phase for say one minute longer to help the bean mass to be more "homogenous" (sp?). That in turn makes the 1C a bit more concentrated...
Of course you can try a 10-12 oz roast if you think that is the problem. I still don't think that it would change the 1Cs, but it would be interesting to hear about your results.

[Slayton]

Different beans react differently and hit stages at different temps.  I have some beans that I roast that have a few outlier beans reach FC at as low as 195C and full rolling FC at 199C or so.  Others don't reach full rolling FC until 204C.

If your J tube is filling with chaff I would think that you need to increase air flow.  Again, different beans different amount of chaff with some much less and some much more.

[dickcoffee]

I did the second roast, raised the air flow and made sure the j tube was clear. Same behavior. I'm telling you, these beans are huge. And, it's true, first crack varies, but this was an extraordinarily late 1st crack. I have done close to 200 roasts on this guy and never had anything later than 390.
Anyhow, I pulled a shot today as an Americano and it was delicious. Sweet and fruity. Alls well that ends well.

[hankua]

Roasted bean volume is a metric along with green beans; for density. Under Artisan Roast Properties there's a calculator for volume in/ volume out.

Pacamara beans are also called "elephant beans" and it makes sense a pound of these guys is going to have more volume. The roasting drum capacity is more about volume than weight; as the green beans don't fill it up initially (in addition to heat distribution).

Although the volume differences are usually slight with our small quantities, it's noticeable to the big guys who fill up trash cans with roasted coffee.

Joe Marocco (Mill City Roasting School) had a good discussion on bean density, when Dave was out recovering from surgery.