The Ultimate Home Roasting Guide

So why would we, a coffee roasting company, tell you everything you need to know about roasting coffee at home?  Well, we think it's fun and chances are you'll just grow to like coffee even more because of it!  Plus, I, Brice, started as a home roaster.  If we can help bring another passionate person into the fold of Specialty Coffee through home roasting, then that is way more important then selling you an occasional bag of roasted coffee!  So... there's a lot to know, but we're going to lay out the basics you need to start roasting coffee at home!  

Why roast coffee at home?

1) You save money!  Green coffee is more then half the price per pound of roasted coffee.  So not only will you save money on that front, but also you'll cut down on your waste becasue you will be able to completely control your freshness!  Instead of buying a bag of coffee that is already 3-4 days off roast, you can roast your own and have it a few hours off roast!  Secondly, you'll be able to roast the exact amount you need.

2) You can roast specifically to your taste! Once, you've spent some time developing your skills, you should be able to roast the coffee exactly to your liking.  Again, I say - once you've developed your skills!  It will take some time before your coffee tastes "right," but from there you should be able to tweak it to create a coffee perfect for you!

3) It's a great hobby that will exponentially expand your coffee knowledge.  Because of home roasting, you'll be a much more discerning coffee drinker overall.  Knowing what goes into roasting will help you appreciate and enjoy professionally roasted coffees that much more!  If you want to expand your brewing knowledge, check out this post!  

The Basics

To break it down very simply... basically coffee roasting is taking an incredibly dense, moist, and unpleasant tasting green seed and transforming it into a brittle, soluble, volatile, aromatic, roasted seed with a pleasant tasting balance of acids and sugars.  So that's what you need to accomplish... and you can make that happen in very simple ways without controlling many roasting variables, or you can make it really complicated and have complete control over a great number of variables.   Towards the end of this post we're going to lay out a few different home roasting methods with varying degrees of variable control.  

The Overall Process

No matter which way you choose to home roast, your beans will follow a specific process.  Roasting begins when you contact room temperature green beans with a hot surface and begin heating them.  This is called the "charge."  At the beginning your beans will still be holding onto a lot of moisture which is helpful in creating "inner bean development."  Basically that means you want to cook the inside of your bean as well as the outside.  So, the high water content at the beginning will help when you pair that with conductive heat.  I know, I know, we're getting pretty deep here... but it really is simple!  Conductive heat is when heat transfers through contact... hot surfaces, bean to bean.  So all that to say, you want more conductive heat in the beginning of your roast.  So if your home roaster has a way to manipulate airflow, I would say at the beginning try to keep airflow at a minimum.  As the beans start to heat through conduction heat, they will start to lose some of that moisture in what we roasters call the "drying" phase.  You might actually see a little steam coming from the beans at this point.  The drying phase is characterized by a musty smell and also a slight white hue to the beans coupled with a small amount of wrinkles appearing on the bean.  From there the beans will progress into the "yellowing stage."  You guessed it, they start to turn yellow.  So, we could dive into the chemical changes that start to take place... but we'll stick to the bare bones here and leave the technical stuff for another post.  Now, as your beans progress through yellow, if your roaster has the ability to start applying less conductive heat and balance it with some convection heat, that would be ideal.  Convection heat is heat transfer through air.  As your beans start to turn a tan color, the Maillard reaction will start to take place... this is a complex chemical change that has a huge impact on how you coffee will taste.  Here you will also start to notice some nice fragrant aromas starting to develope.  From tan/Malliard the coffee will then begin to caramelize sugars.  Contrary to popular belief, caramelization does not actually make things sweeter, it destroys sweetness... however, this is a necessary part of roasting and you have to roast a little longer in order to get a nice development of body and sweetness. If you were to stop roasting at the onset of caramelization, then you'd end up with a very wild and mostly sour cup.   Just after caramelization starts, we hit "first crack."  This is characterised by an audible popping sound and this happens when the remaining moisture in the bean gets to such a high temp that the pressure within the bean builds and has nowhere to go so it has a mini explosion.  Here marks the point of a proper development of sugars and compounds that create body and balance. So any time after a few moments into first crack is an acceptable time to stop your roast and could potentially be very tasty.  However, you will find some coffees taste better at different points throughout first crack.  It's important to time your roast and use the first crack as a marker for roast degree.  If you let the coffee keep roasting through first crack, you'll hit a lull where no more popping is happening.  The aromatics and smoke coming from the beans will become a bit more carbon-y smelling and after some time you will hit "second crack."  Basically it's round 2 of first crack, now sounding like more of a snap then a pop, and this is the marker for a dark roast.  Once you've hit second crack, most sugars have been combusted and you'll end up with a very rich body and little acidity in your cup.  Some people like the smokiness that second crack brings on, and you can push into second crack pretty far... however the beans have lost a lot of weight and are VERY hot at this point so controlling your roast through second crack is next to impossible and the only thing that can happen from here is to light you batch of coffee on fire!  So approach second crack slowly and don't let your roast go too much further. If you want to learn more about the process of roasting, check out The Coffee Roaster's Companion book by Scott Rao.   So.. that's basically the process, now how do you do it?

The Rules of Home Roasting

1) Always keep a log!  Make sure to record the following: the name of the coffee, the weight of your green coffee and the roasted coffee it produced, the time of each roast and note the times of yellow, first crack and, if you go this far, second crack.

2) TASTE your coffee and also record your notes on flavor.  It's imperative to taste your roasted coffee and start to figure out what variables in roasting cause what changes in the final cup.  Clever Drippers are a great brewing method to check your roasts with!  Learn how to use a Clever Dripper brewer here!

3) Be consistent and only change one variable at a time.  Consistency is one of the most important things in roasting!  Also, when you do taste your coffee and want to try and tweak something, try to keep your roast consistent with the last one and only change one variable at a time.  For example, if you change the total time, final color, and amount of coffee you use, you wouldn't be able to attribute a change in flavor to any one of those variables.  

Home Roasters

All you need is a kitchen scale and then check out these widely different ways to get started!

The Skillet - $0

Want to start roasting right now?  Well, go grab a skillet and turn your stove on!  You can actually roast RIGHT NOW!  This method won't give you the best results, but it will allow you to see how coffee roasting happens right before your eyes!  Also, note it will get a little smoky - skillet roasting works best if you have a vented hood over your stove.  

The West Bend Poppery II - $40  <--- Click to buy!

Yes, you can roast coffee in a popcorn popper... a very specific popcorn popper!  The West Bend Poppery II is the perfect device, it lacks a modern high temp shut off switch and has vents along the side of the chamber that will actually help spin and mix your beans as you go.  Furthermore, the hot cylinder mimics a professional drum roaster in a lot of ways by giving you a great mix of conduction and convection heat.  One of my favorite simple mods for this roaster is to buy a replacement glass for a kerosene lantern and put it on top instead of the stock plastic piece.  The glass helps retain more heat in the device and can help you produce some pretty dang good roasts!  Also, plan to roast outside with this as chaff and smoke will go everywhere! Here's everything you need to roast with this machine:

The Behmor 1600 - $360

The jump from the popper to the "coffee rotisserie microwave," is a big one!  However, the Behmor gives you so much more control!  You can actually do some profiling with this roaster and also roast up to 1lb at a time!  Also, this machine does a fairly decent job of keeping back the smoke and chaff, so you can usually get away with roasting indoors with little ventilation.  The only downfall to this machine as I see it is the lack of conduction heat, the roaster basically has a big basket that rotates and forced air heats the whole whole machine inside... basically straight convection heat.  So, coffee from this machine will always have a little baked flavor.  But hey, it's reliable, simple, and actually designed to roast coffee, haha!  

The Kaldi Roaster - $420

If you can jump the little step financially above the Behmor you can land one of these bad boys!  Disclaimer - I have not yet personally used one of these machines, but from what I told this is the BEST home roaster for the price. You can see temperature readouts, control burner temp well and you also get a GREAT mixture of conduction and convection heat.  Furthermore, the possibilities to modify this roaster and customize it yourself are endless.  It's designed to sit on a gas stove top and use a burner to heat it.  If you don't have a gas stove, you can always buy a butane burner or camp stove.  

The Hottop - $1500

If you're ready to go ALL OUT, check out this beast!  It's basically a mini professional roaster, and the new models come with some really great profiling abilities.  With this you'll basically get full control of almost every variable possible that affects coffee roasting.  I don't know what else to say other then it's awesome!

Do you have a different home roaster or are you thinking about purchasing one we didn't mention?  Let us know in the comments below and we can help!  

Edit: 3/12

My friend Nick from London Saigon Coffee based in Vietnam, just told me about another really great little roaster that is very popular in Asia.  It's called the Lysander sample roaster  and is a lot like the Kaldi above.  It works on a burner system and give you a lot of control over the heat as well as drum speed and such.  It seems like a great little machine, I'd recommend heading to their site if you're interested in one to get some more information.  I'm unsure of the price and it looks like ordering is handled through emailing the company.