How is roasting coffee with Kelvin different than roasting with a popcorn popper?

There are several things that differentiate Kelvin from a typical hot-air popper.

First is that we give you control over the roasting time, allowing you to adjust that time during the cycle to get your ideal roast.

Second, as soon as the roast time is completed, Kelvin starts an automatic cooling cycle. This prevents the beans from roasting more than desired, even after the heat is turned off.

Third, Kelvin collects the chaff put off by the beans during the roasting process, making clean-up between roasts simple and easy.

Lastly, the glass roast chamber allows you to see the beans during the roasting process so you can easily monitor the color, which is something that you don't often get with hot air poppers.

This all adds up to a great roasting experience, so even the most novice roaster can explore the freshness, flavors and value of home roasting.

How much coffee can Kelvin roast at a time?

The ideal batch size for Kelvin is 100-120 grams of green beans. That yields enough roasted beans for a pot of coffee, depending on the darkness of your roast, method of brewing and preferred water to coffee ratio.

Does Kelvin support custom roast temperatures / profiles?

To set up a roast with Kelvin, you simply select the roast time and Kelvin does the rest by controlling the heating element to achieve a specific, pre-set roasting temperature and then maintains that temperature for the duration of your roast. Our roast temperature is currently ~400F, but may be optimized in final manufacturing. Kelvin then triggers an automatic cooling cycle at the end of the roast.

We designed this process to simplify the user experience and keep home roasting more accessible to anyone who is interested. We are considering additional features, such as custom roast profiles, as we expand the future Kelvin line of products. Our current focus is to first launch this accessible, intuitive roaster that all coffee lovers can enjoy.

What are some details of the green bean subscription, and the beans that will be sent?

We are still finalizing the details of the green bean subscription service. We anticipate an average cost of 6 USD per pound (about $13/kg) for green beans, with some variations for different regions and sources. We are working with distribution partners to understand the shipping costs and any potential customs or other restrictions.

We are planning on providing beans from a wide range of regions (from Central and South America to Africa, India and Southeast Asia) and sources (from certified organic, fair trade, and small farms to more affordable options from larger wholesalers).

Most coffee roasting professionals recommend a “rest” period after roasting for best flavor. How does Kelvin support that?

In our research and testing, we have encountered a wide variety of opinions and data regarding the "rest" period, ranging from 12-24 hours to 5+ days, and varying depending on the region the green beans are grown in. There are even all-in-one solutions on the market that grind and brew the beans immediately after a roast is completed. We encourage Kelvin users to experiment and find the Roast and Rest periods that work best for them to achieve their preferred flavor.

How does Kelvin deal with the smoke generated during the roasting process?

We kept the batch at a smaller size (100 to 120 g of green beans) and our prototypes have proven we can minimize exhaust. Kelvin is similar to other products that toast or cook things in your kitchen—you will be able to smell the beans roasting, a preview of that perfect cup of coffee.

Will the plug be compatible with the plugs in my country?

Your Kelvin will come with the appropriate plug for the country you select in the backer survey, which will be sent soon after the end of the campaign.

Why can I not select Japan as my country?

Unfortunately, due to Japan's unique electrical grid that runs on 100 V, neither of Kelvin's power variants (110-120 V and 220-240 V) will work correctly in Japan, so we are unable to offer Kelvin to Japanese backers at this time. Please check our updates for any announcements of additional international versions.

What materials does Kelvin use?

We expect Kelvin will live on countertops, so we designed it to have beautiful parts, elegant color selections and high-quality materials. Kelvin is constructed with special attention paid to have only high quality materials in contact with the roasting beans. Here are some specifics:

  • The roasting chamber and out safety chamber are high temp borosilicate glass
  • The roast chamber inlet (bottom of roast chamber), the chaff filter (inserted in top of roast chamber) and roast chamber top cap handle handle are aluminum components
  • The base housing and top cap are high temperature engineering grade plastics with a soft-touch finish

How does the dual-wall glass design impact the roast?

The dual glass wall design helps protect the user from the heat of the roast and stabilizes the roast chamber. It is not a full insulation break, so there is minimal effect on the cooling cycle, and it does not significantly hinder users’ ability to hear first or second crack.

What is included in the shipping cost?

The shipping charges on your pledge include transportation only. Due to the complexity of various international customs regimens, we are not pre-collecting any customs duties/tariffs or local VAT or sales tax. These will be the responsibility of the recipient upon delivery, and may be subject to fees charged by the shipping carrier.

How much weight do the green beans lose during roasting?

Green beans do lose some internal moisture as they are being roasted. There are a few factors that go into weight loss during the roasting process such as type of green bean and roast development level (light vs dark). In our testing we see between 15%-20% on average. Your results may vary as in our research and testing we've seen this range as low as 12% all the way up to 25% for darker roasts.

How can I make changes to my Kelvin pre-order?

If you pre-ordered Kelvin as a backer of our Kickstarter campaign (before May 12, 2018), you can make any changes to your order through Kickstarter. This includes making changes to your shipping address, payment information for any add-ons you’ve ordered, and, of course, ordering more add-ons!

If you pre-ordered Kelvin after we closed our Kickstarter campaign (after May 12, 2018) via this website, you can make changes to your order through our PayWhirl customer portal (PayWhirl is our pre-order partner). This portal is new as of June 6, 2019, but rest assured, your pre-order information is safe and sound. To access the customer portal, log in using the email address you used when you placed your pre-order. If you placed your pre-order before we set up this portal, you’ll need to change your password to gain access the first time you log in (our system set your password to a unique, randomly generated password that not even we know).

How can I access the PayWhirl customer portal?

You can access the PayWhirl customer portal at Use the email address you used when ordering Kelvin to log in, along with the password you selected.

If you placed your pre-order before we set up the portal (before June 6, 2019), you’ll need to reset your password to get started. To do this, click the link on the login screen that says, “Forgot your password?” and follow the steps to reset it.

Why is my PayWhirl pre-order called a “subscription”?

In PayWhirl, a pre-order is considered a subscription with a single delivery date. For Kelvin, we’ve also set them up with a single payment date, which will coincide with shipment. When you place a Kelvin pre-order in PayWhirl, there is an initial “fee” of $0 so that we can store your credit card information. When we’re ready to ship, we’ll charge you the balance (the cost of the Kelvin items you’ve purchased plus applicable shipping and tax). This will be a one-time charge on the card we have on file, not a recurring subscription charge.

How are you storing my credit card information?

Regardless of whether you ordered your Kelvin via Kickstarter or via this site, your credit card information is being stored securely in Stripe. We do not have access to your credit card information; only you can make updates to it via one of our pre-order channels (Kickstarter or our PayWhirl customer portal).

What will happen when Kelvin is ready to ship?

When Kelvin is ready to ship, we will process all of the pre-orders we’ve received. For each Kelvin pre-order customer, assuming we are able to charge their credit card successfully, we will ship Kelvin to the shipping address we have on file.