oldgearhead Senior Member Joined: 25 Jan 2010 Posts: 382 Location: Go Colts! Expertise: I like coffee
Grinder: Virtuoso by Baratza Drip: Chemex,Dilongi DCM900 Roaster: 1/2K Fluid-bed
Posted Tue Nov 12, 2013, 5:44am Subject: Re: Fluid bed vs Drum--why different curves?
Of course another 'feature' of a fluid-bed roaster is you can adjust the roast by either the air-temperature control, the air-flow control, or both. I started out with my fluid-bed roaster by adjusting the flow control twice, at 3 minutes and 6 minutes, also I set the air temperature three times: 470°F, 650°F, and 580°F (drying, ramp-to-first-crack, and finish). Recently, however, I've been setting the temperature based on the density and test weight of the bean being roasted and adjust only the air-flow during the roast. Example (SHG bean): I set the air-temperature at 550°F, turn the air-flow down at T+ 3 min., again at T+ 6 min. and turn it up at T+9 min. The roast Bean Mass Temperature (BMT) responds much quicker to air-flow changes than to heating-element current changes in my heat-reclaiming, electric, 120V, one-pound, fluid-bed roaster. In general the curve I'm using now is very similar to the one I started with:
July 2011 __T+0 = Drying, 4 min. (470°F) __T+4 = Ramp-to-first-crack, 4 min. (650°f) __T+8 = Finish, 3-4 min. (580°F)
July 2013 Air-temperature = 550°F Adjust air-flow only _T+0 = Start Drying _T+3 = turn down to 'creep' _T+6 = turn down to 'creep' _T+ first crack = turn up
However, the drip coffee is a bit more full-bodied, and sweeter. It seems that I get a much more complex cup when I use lower air temperature to move first crack from T+8 minutes to T+ 9.5 minutes. ___________________________________________________
Symbols: = New Posts since your last visit = No New Posts since last visit = Newest post
Forum Rules: No profanity, illegal acts or personal attacks will be tolerated in these discussion boards. No commercial posting of any nature will be tolerated; only private sales by private individuals, in the "Buy and Sell" forum. No SEO style postings will be tolerated. SEO related posts will result in immediate ban from CoffeeGeek. No cross posting allowed - do not post your topic to more than one forum, nor repost a topic to the same forum. Who Can Read The Forum? Anyone can read posts in these discussion boards. Who Can Post New Topics? Any registered CoffeeGeek member can post new topics. Who Can Post Replies? Any registered CoffeeGeek member can post replies. Can Photos be posted? Anyone can post photos in their new topics or replies. Who can change or delete posts? Any CoffeeGeek member can edit their own posts. Only moderators can delete posts. Probationary Period: If you are a new signup for CoffeeGeek, you cannot promote, endorse, criticise or otherwise post an unsolicited endorsement for any company, product or service in your first five postings.