Controlling Roasting Variables

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Controlling Roasting Variables

Let’s face it: roasting is one of the most challenging parts of the coffee-making process. Even if you’ve been roasting for a while, there are always new variables to keep tabs on and learn how to control. Luckily, there are plenty of resources out there to help you tweak your roast profile in order to create a final product that meets your exacting standards. In this article, I’ll go over some tips for adjusting the roast length and temperature while also touching on airflow and cone dropping in order to control roasting variables.

Roast Temperature

The temperature of your roasting machine is measured in degrees Fahrenheit (F), and it varies depending on what kind of bean you’re working with and what roast style you want. The recommended range for most coffees is between 400-500 F, though some high-quality specialty beans require lower temperatures than that. If your coffee tastes burnt or bitter, try lowering the heat; if it’s bland and flavorless–or even sour–you may need to raise it slightly.

The minimum temperature at which you can roast coffee depends largely on how much heat is generated by your roaster itself; for example, electric models tend not generate enough heat on their own and will require an external source such as an oven hood fan or propane burner to keep things going at all times during the process (although this can be dangerous).

Length of Roast

The length of the roast is one of the most important variables in coffee roasting. It can make or break your final product, so it’s important that you understand how it works.

  • The longer the roast, the darker your beans will become. This is because as heat increases in intensity, so does its ability to break down cellular structures in coffee beans and release their flavor compounds (and other chemicals). More intense heat is applied during roasting processes like French Press or stovetop espresso makers than those used by electric drip brewers such as Nespresso machines (which use near-boiling water), which means that these styles require less time for optimal results.*

The longer a bean spends in an oven also means more caffeine will be extracted from its cells due to increased exposure time.* This means stronger flavors overall — but also increases risk of burning if left unattended too long.*


In order for the roaster to work properly, it needs to be able to pull air through the beans. This is achieved by creating a vacuum inside of your roaster and then allowing that vacuum to be broken with fresh air as it enters through an intake vent. The more air you can get into your roaster, the faster your beans will roast–but if they’re not moving fast enough when they hit those temperatures (which means you either need more heat or less time), then they’ll burn instead of caramelizing properly.

You can control airflow by adjusting how much pressure there is inside of your machine:

  • For example, if you want hotter temperatures faster but don’t want them too high because they’ll dry out any moisture left behind in each bean before its done roasting; try adding more pressure so there’s less room for cool air around each individual bean when heating up

Cone Dropping

Cone dropping is the process of removing the beans from their roasting chamber. It’s important to do it correctly, as it can have an impact on flavor and color. The goal is to drop them into a cooling tray without letting them get crushed by other beans, which will happen if you try to dump them all at once. If you’re using one of our machines with a cooling tray (like our standard or pro models), simply remove the lid of your roaster and start pouring out coffee in batches onto your cooling tray.

If you don’t have a cooling tray like this one, use something else that will allow air flow around each batch as it cools–a metal colander works great for this purpose! We recommend pouring out small batches every few minutes until all of your beans are gone; this keeps everything moving so nothing gets too hot or stays too long inside before being dumped out onto whatever surface serves as “ground zero” for this operation (read: any flat surface).

Looking at the Chart

The chart below shows how roasting temperature, length of roast, and airflow affect the bean. The bean’s color is plotted on one axis and weight on another.

The red line represents an ideal roast profile: it begins at a relatively low temperature (around 400F/200C), ramps up quickly to around 500F/260C where it stays for most of the roast, and then drops back down again as you finish off your coffee.

Practical advice: if your coffee tastes too dark or sour, try reducing your oven temperature; if it tastes flat or lacking aroma, increase your oven temperature slightly; if there’s too much bitterness from over-extraction–a common problem with dark roasts–reduce airflow during the first half of roasting before increasing air flow toward the end so you can cool down quickly without losing all those aromatic oils from overheating them!

Controlling Roasting Variables with these tips

  • Use the chart to guide your roasting.
  • Pay attention to the chart and make adjustments based on what it tells you.


We hope this article has helped you understand the basics of roasting. It’s a complex process, but with some practice and patience, you can start to control roasting variables and make great coffee at home!