How to Scale a Roast Profile When You Move to a Bigger Roaster: 7-Step Guide

You finally have the bigger roaster. Maybe it's a 15 kg drum taking over from a 3 kg shop machine. Maybe it's a 35 kg production roaster replacing a 12. Either way, the next question is the same. How do you scale a roast profile so your coffee tastes the same on the new machine?

The short answer is that you don't copy the curve. You copy the outcome. A bigger roaster has more mass, a different burner, different airflow and a probe in a different spot. The numbers on the screen won't line up. The cup can.

We see this step up every week at CoffeeTec. CoffeeTec listed 89 roasters from November 2025 to October 2026. Of those, 39 were in the 5 to 18 kg range, more than any other size tier. Each of those machines is a step up for its next owner, and each step up brings the same job after delivery. This guide shows what carries over from your old roaster and what has to change. Then it walks through seven steps to rebuild each profile on the bigger drum.

Key Takeaways

• A roast profile never transfers 1:1 between machines. Treat the old profile as a set of targets, not settings.
• End color, weight loss and development time carry over. Charge temperature, gas settings and airflow do not.
• Bigger batches usually need a slightly slower roast to avoid heat defects like scorching and tipping.
• Most roasters work inside a batch window of roughly 25 to 80% of the rated drum size.
• Match every milestone from yellowing onward. The early drying phase is where the new machine is allowed to differ.
• Change one variable per batch, then cup the old and new roasts side by side before you lock a reference profile.
• A sample roaster helps you set targets for each coffee, even though its settings won't copy across either.

Why a Roast Profile Doesn't Copy 1:1 to a Bigger Roaster

A profile is a record of how one machine put heat into one batch. Change the machine and almost every input behind that record changes with it.

Mass changes the math. A bigger batch needs more total energy, but each bean can only take so much heat before it shows defects. A customer once asked Mill City about moving from an 8 lb roaster to 20 lb batches. In its reply, the company explains that bigger batches have to roast a little slower to avoid heat damage. The same post adds a useful point. A 10 kg machine can run much closer to a 1 kg profile than a 20 kg machine can. In other words, the bigger your jump, the more the profile has to stretch. The illustration below shows the pattern: drying runs longer on the big drum, then every milestone after yellowing lines up.

Probes don't read the same. A bean probe measures the beans and the air around them. Its depth, position and how well the bean pile covers it all change the reading. So 200°C on your old roaster and 200°C on the new one are not the same moment in the roast.

Airflow and build differ. Drum diameter, wall thickness, fan power and even exhaust duct length change how heat reaches the beans. A heavy double-walled drum stores far more heat than a light shop roaster. That stored heat carries momentum from batch to batch.

What Carries Over and What Has to Change

Split your current profile into two lists before you roast a single batch on the new machine. The first list is your target. The second list you'll rebuild from scratch.

How to Scale a Roast Profile in 7 Steps

Start with your best-selling coffee, usually your house blend. Rebuild that profile first, then use what you learn for the rest of the menu.

1. Write down your targets, not your settings

Pull your roast logs for each coffee. Record end color, weight loss, total roast time, time to first crack, development time and your cupping notes. Color is the anchor here, so measure it the same way every time. Our guide to the Agtron scale and roast color numbers covers how roasters read and compare color.

2. Learn the new machine before you roast your best coffee

Give the roaster a full warm-up. Then run several batches of inexpensive or seasoning coffee at about half capacity. Watch how fast it heats, how it responds to gas changes, and how much the temperature drops between batches. You're learning the machine's momentum. Don't use your top single origin for this.

Settle on a between-batch protocol too. Let the drum drop to the same temperature before every charge, then bring it back up the same way. The first batch of the day often runs differently, so treat it as a warm-up and keep it out of your comparisons.

3. Pick a batch size inside the working window

A rated "15 kg" drum is a maximum, not a target. A Roast Magazine feature on batch size quotes consultant Anne Cooper on her rule of thumb. In theory, she treats 25% of the rated drum as the ideal minimum and 80% as the ideal maximum. The same feature shares a rough check from Scott Rao for traditional drum roasters. Plan on about 5,000 BTU per hour of burner output for each pound of green per batch. That gives you a ceiling to stay under while you learn.

Pick one batch size and stay with it until the profile works. Changing batch size and profile at the same time hides what's actually going on.

Enter your new roaster's drum size, burner rating and your old roast timings below. The planner gives you a working batch range and the milestones to aim for.

4. Set charge temperature and gas for the bigger batch

Begin with the manufacturer's suggested charge temperature for your batch size. More mass pulls more heat out of the drum at charge, so the turning point will come later than you're used to. Does the early roast stall? Add heat earlier with a higher starting gas or a shorter soak. Avoid a much hotter charge. A very hot charge in a single-walled drum is how scorching starts.

Once the profile works, you may still vary batch size day to day. In the same Roast feature, Cooper's starting rule is about 10°C (18°F) of charge temperature per kilo. That applies to each kilo you add or remove on that machine. Treat it as a first guess, then confirm on the next batch.

5. Match the milestones from yellowing onward

This is the most useful rule in the whole process. Cooper describes testing coffee on a Probat P12 at 4 kg, then roasting a full 12 kg batch. Time to yellowing could shift by around 30 seconds. After yellowing, she holds everything else the same: time through the Maillard phase, first crack, development time and end color.

Use that as your scaling method. Let the drying phase run a little longer if the bigger batch needs it. Then steer gas so the rest of the roast lands on your old timings.

6. Adjust airflow and drum speed last

Airflow changes how much heat moves by hot air versus contact with the drum. On a bigger roaster it also clears smoke and chaff from a much larger bean pile. Change airflow only after timing is close, and change it by one step per batch. Note every change in your roast log so you can trace what moved the cup.

7. Cup side by side and lock a reference profile

Roast the same green on the old and new machines on the same day if you still have both. Cup them blind next to each other. Our walkthrough on how roasters run a cupping session lays out a clean protocol for this. When the new roast matches or beats the old one, save it as a reference profile. Artisan, Cropster and RoastPATH all support this. Then follow it batch after batch.

Using a Sample Roaster to Bridge the Gap

A sample roaster won't hand you a production profile either. ROEST put the question to roaster Tim Wendelboe. He said converting a small batch profile directly to a bigger batch isn't really possible. What a sample roaster does well is teach you the coffee. You learn which color, development time and weight loss taste best. Then you aim your production profile at those targets.

Machines from the same family translate more closely. Mill City builds its MCR-500 sample roaster with the same controls as its larger machines. San Franciscan designs its SF-1 in proportion to its bigger models. That shortens the learning curve, though you'll still fine-tune on the production drum.

Sample roasters are one of the most requested categories on CoffeeTec. We received 365 quote requests from January to October 2026. Of those, 64 were for sample and small profiling roasters such as the Aillio Bullet, ROEST and Probat lab models. Browse current used sample roasters if you plan to profile new lots without tying up your main machine.

Scaling Across Size Tiers

How much rework you face depends on the size of the jump.

From 1 to 4 kg up to 5 to 18 kg. This is the most common upgrade. Expect a longer drying phase, a bigger burner to learn and much more stored heat between batches. Plan to rebuild your house blend first, then work through the menu one coffee at a time. If you're shopping this tier, see the current medium batch roasters (5 to 18 kg).

From 5 to 18 kg up to 20 kg and beyond. The batch is heavier, cooling takes longer and automation starts to matter. Many production roasters at this size replay saved profiles through software. The reference profile you lock in step 7 becomes the instruction the machine follows. Current options sit in our large batch roasters (20 kg and up) collection.

Changing roaster type at the same time. Moving from a single-walled drum to a convection roaster like a Loring changes how heat reaches the beans. Treat this as a new profile built from your flavor targets, not a scaled version of the old one.

Common Mistakes When Scaling a Profile

• Chasing the old temperature numbers. The probe reads differently on the new machine. Match color, timing and taste instead.
• Loading the drum to 100% on day one. Start near half capacity, learn the machine, then build up.
• Changing gas, airflow and batch size in one roast. You won't know which change did what.
• Rebuilding the whole menu at once. Get the house blend right first. The other coffees go faster after that.
• Retiring the old roaster too early. Keep it in production until your core profiles hold on the new machine.
• Skipping the cupping table. A matching curve means nothing if the cup changed.

Plan the Profile Before You Buy the Bigger Roaster

The easiest scaling projects start at the listing. Before you commit to a machine, check its burner rating against your target batch size and confirm it has adjustable airflow. Ask whether it has a data port for logging software. Then compare its drum style with what you roast on now. Our guide on what size coffee roaster you need helps you pick the right tier from your weekly volume. Then read how to buy a used coffee roaster for the inspection questions to ask.

Still deciding if the move makes sense? Our guide to the signs it's time to upgrade your coffee roaster covers when to size up. It also shows how to time the sale of your current machine. Your old roaster is often the exact size another café needs to start roasting. Once your new machine has a ship date, you can list your current roaster on CoffeeTec and hand it over once your profiles are dialed in.