Coffee Roasting At Home - 121031

I've made a new chaff collector by cutting out both ends of a tin can, drilling a 2" hole to fit over the glass chimney, and attaching 2 bags made of wire window screen (one to each end of the can).  I also punched a hole for the temperature prove positioned so that the probe rest about 1.25" above the roasting bottom.  Here's what it looks like:

The wire bags should provide plenty of surface area for chaff collection.  They can be emptied by using a vacuum.  The bags are attached with an outside twisted wire loop.  I also taped the assembly with high temperature aluminum tape, not the stuff that failed.

There is a trick to forming the bags.  I folded the wire seam over itself a couple of times so the portion given to fraying is inside the fold.  Then simply use a stapler to 'bind' the seam.  What it lacks in pretty it makes up for in quick/easy/effective.

I also added some twine as an insulated handle to the glass chimney in case I need to remove it to dump the beans for cooling.  My current cooling plan is to turn off the head and run the fan for 4 minutes on full.

Related articles

• Coffee Roast at Home - Part 3 121030
• Coffee roast at home - Part 2 121020
• Coffee roasting at home - Part 1

Coffee Roast at Home - Part 3 121030

I've continued to work on coffee roasting at home.

After my initial roast, I decided to modify my popcorn popper as described in here and particularly here.  Here's what I've done.

Here's the machine unmodified.

Step 1: Take the machine apart and verify the wiring prior to modification.

Bottom held on by 4 small philips head screws.

Unmodified wiring.

Motor base.  AC, ~17v in with diodes to turn to DC.

Popper internals.  White part is base holding fan.  Central black part holds heating elements.  Top silver part directs hot air up.  Assembly held together with 4 screws.

Schematic.  Note two heating elements with 40 ohm element in series with motor.

Heating element on base

Heating element removed from base

Top of popcorn roasting chamber.  NOTE: This is not the kind of recommended roasting chamber and is said to pose a fire hazard.  So far I've not had any issues.

Step 2: Make the modifications.

After taking the wire nuts off, I rewired with independent circuits for each of the two heaters and a third circuit for the motor. 

Used a cable tie as stress relief.

 Step 3: Make the control box.

Used a large work box to hold the controls.

Cut the unwanted tabs off and drilled a small hold for AC to the controls.

 This is the schematic I worked off of.

I was able to find AC switches with a built in red/green indicator light at Radio Shack.  The schematics on the part bag are a bit confusing.  L/N are an international standard for line/neutral.

Part 275-0021, 16A, 125VAC

Mounted everything on a small board with  transformer external (a bit of testing showed that the transformer  got somewhat warm).

Components mounted and wired.  There is a fair bit of wire so having a large box was helpful.

 That's it for the basic modifications.  I also decided to replace the plastic top that came with the popcorn popper with a glass oil lamp chimney and provide a temperature probe to monitor roast temperatures.

Glass chimney and probe.

I made a sheet metal collector for chaff with a screened section to vent smoke.  This didn't work (see below).

Time to test.

100 g of beans

Setup under stove hood

The roast went well as I controlled temperature by pulsing the heaters.  Here are the results.

All in all things worked OK.  Here's what I've learned.

• The fan will run much faster.  DC voltage across the unmodified motor was 17v.  After modification it was 25v.  The motor had some part information on it but I was unable to actually read it.  I suspect that it is a 24v DC motor and am hopeful that it will operate ok as modified.
• I'm a bit uneasy about switching the heaters on/off.  My concern is the physical stress this might create in the heater elements.
• I need a roasting PLAN!  Now that I have control of the heaters and fan I should have some idea of what I want to do by way of a time/temperature profile.
• The chaff collector didn't work well.  There were several issues.  The aluminum tape, really paper tape with an aluminum backing, failed.  The screen area, about 6 square inches became clogged and chaff blue out of the sheet metal seams.  I clearly need a better chaff collector!

Related articles

• Coffee roasting at home - Part 1
• Coffee roast at home - Part 2 121020

Sandy

The storm came and went.  Fortunately, for us, it was just some strong winds and heavy rain.  Power stayed up, largely due to last years wet snow having already brought down anything likely to fall.  It looks like we'll have rain from the storm for another two or three days as the storm track loops around the NE.  All in all though things are good.

Coffee roast at home - Part 2 121020

I decided to roast another batch of coffee.

Modified popper with 1/4 in. screen to keep beans from flying out.  The screen generally works well.  Beans stay in and chaff escapes.  Some minor adjustment will likely be needed.  Screen held in place with a copper wire.

Screen to keep beans in popper.

Dropped 78g of green Mexican.  This is enough to fill popper to popcorn full line.

78g green Mexican

This time I put the popper and chaff collector next to the stove with the hood running.  This is a considerable improvement but the area still smelled of something burnt or so says BB.  Paper towel is wet to catch chaff and that works extremely well.

Setup next to stove with wet paper towel to catch chaff.

I ran the roast as follows:

• 1:40 Beans showing color but uneven.  Some beans definitely appear burnt.  Had to shake the popper to improve agitation.  Not a big issue but I'd like more agitation. 
• 2:16 1st crack starting.  There is PLENTY of heat in this roaster given the air flow.  Would like more air flow so 1st crack is 6 to 8 minutes and second around 10 to 12 as we run at Karma.
• 3:20 Smoke visible with extended cracking.
• 4:00 Crack running solidly.  First to second crack happened instantly.
• 5:00 Dump.  Serious smoke.  This machine runs WAY TO FAST with 78g of beans.  More air flow needed and likely more beans.

Plastic cover was VERY hot and I slightly deformed it when I took it off to dump beans.  I'll need an insulated handle.

The yield was 62g. That's a 16g roast loss, 20.5%.  At Karma we drop 16 lbs and get 13 yield for a roast loss of 3 lbs, 18.75%. 

62g finished roast

The wet towel chaff collector worked well.

Chaff on wet paper towel.

Here's what the coffee looks like.  Solid dark with uniform color.  Post roast smell was good.  I'll cup it Tuesday.

Beans, Full City + perhaps ++

A couple of things of note on this popper:

• More air flow to float a larger load since there is plenty of heat
• Insulated handle on plastic so it can be more easily removed.  I suspect replacing the plastic with a glass chimney makes a lot of sense though I'll need to work out some way to catch the chaff.

First coffee

Two days ago I roasted some coffee (Mexican).  The beans have oiled up nicely so this mourning I decided to try the coffee in a Latte.  I ground 23g fine and fired up the espresso machine.

This is a VERY inexpensive machine I've had for some while.  It makes an OK cup of steamed coffee, not really espresso as there's no crema (foam).  Still I like the coffee.  I steamed some milk and in short order had a sort of latte. 

Yum - tasted very good.

All in all I'm entirely satisfied with the first roast.  I'll roast again tomorrow so I'll have coffee for a filter brew Monday.  Meanwhile, I'm going to work on the screen to keep the roasting beans in the roaster.

Coffee roasting at home - Part 1

I've been working for some time at Karma Coffee in Sudbury, Ma.  Great coffee!

My original hope was to work there and learn how to roast coffee.  While I've learned a bit most of my time was spent reconditioning a Probat roaster.  While it's been interesting I'm still interested in learning how to roast coffee.

To that end, I've decided to try to roast coffee at home.  Sweet Marias is the go to place for home roasters.  They've a section on home roasting.  After a bit of reading and searching the net I decided to try a popcorn roaster as a first effort.

I ordered a Orville Redenbacher by Presto hot air popcorn popper which just arrived.  Karma provided some Mexican beans, chosen because they are uniform due to water processing and generally easy to roast.  I've also ordered a high temperature oven thermometer, coffee roast to about 450F, and a book on home roasting that Dave at Karma recommended.  Those should be here early next week.

Meanwhile, I decided to try roasting.  Here's  what the popcorn popper looks like.

I put some beans in to the roaster's fill line and plugged it in, there's no on/off switch so I'll have to think about adding one.  The first thing that happened is that beans started to fly out!  The hot air entrance to the heating chamber is rather small and I suspect the air flow/pressure is high with the result that beans fly out.

I tried adding more beans but all that did was stop the beans from moving at all.  Not good!

I have some 1/4 inch screen on hand so I took a small piece and used it to shield the cooking chamber.  Now no beans come out and the screen is course enough that most of the chaff escapes.  I set a large bowl with a damp paper towel in it underneath the spout and that seems to be reasonably effective at catching the chaff.

I was rather lax about timing but the Mex beans got to first crack in 4 to 6 minutes.  I suspect that I had to many beans to get a decent suspension.  Second crack started at about 10 minutes and by twelve there was much smoke and I stopped the roast.

I used a large pizza pan to cool the beans and that seemed to work well.  The beans were solidly in second crack as I dumped.  That said, the roast color was a bit uneven (to many beans?).

The only other issue is that roasting coffee smells like, well, roasting coffee.  I neglected to turn on the exhaust fan to begin with with the net result that the entire house now smells of roasted coffee.

All in all, as a first effort I'm reasonably satisfied   Yield was 75g of roasted coffee (not sure about the input weight but it should have been about 90g).

Tomorrow I'll get some Mex from Karma and then brew and taste both the Karma and my roast to see what is what.

When the thermometer comes in I'll put it into the roaster.  I'll also find a timer and a better screen (the current one is galvanized and I'd prefer stainless).