Lab Rat: Build Your Own Custom Roast in NZ (Pick Beans, Pick the Crack)
Lab Rat is Naki Roast's custom 1kg coffee service where you blend four bean origins by percentage and choose between 1st Crack (lighter, acidic) or 2nd Crack (darker, smoky) roast levels. The bag costs NZ$60, is roasted to order, and ships in hand-stamped packaging. The lighter you roast, the more of that green weight you keep; push to 2nd Crack and the same beans come out lighter. You select from Brazil Cerrado, India Soft Touch, Mexico Altura, and Colombia Medellín Excelso beans.
What is Lab Rat? Naki Roast's Custom Roast Experiment
Lab Rat is a service from Taranaki-based roaster Naki Roast that lets you design your own coffee blend and roast level from scratch. It's an experimental offering for coffee enthusiasts who want to go beyond pre-set blends and take control of every variable in their cup [1][2].
The service is roast-to-order: nothing sits pre-roasted on a shelf waiting for you [3]. That, combined with hand-stamped packaging, fits the small-batch, artisanal approach Naki Roast brings to every bag [1]. If you've ever wanted to play roaster without buying a drum roaster, Lab Rat is the closest you'll get from a New Zealand specialty coffee provider.
Step 1: Pick Your Beans, Building a Custom Blend
The first decision in the Lab Rat process is selecting your bean origins and assigning percentage weights to each. You work with four specific green bean origins and must allocate percentages that total 100% across your blend [1][4].
Here are the four origins available:
| Origin | Characteristics | Availability |
|---|---|---|
| Brazil Cerrado | Nutty, chocolate notes | Included in Lab Rat |
| India Soft Touch | Low acidity, heavy body | Included in Lab Rat |
| Mexico Altura | Clean, light body | Included in Lab Rat |
| Colombia Medellín Excelso | Balanced, fruity | Included in Lab Rat |
- Decide your flavour direction. Want a rich, chocolatey base? Weight Brazil Cerrado heavily. Want brightness and fruit? Lean into Colombia Medellín Excelso [1].
- Balance body and acidity. India Soft Touch adds heavy body and low acidity. Mexico Altura contributes a clean, lighter mouthfeel [1].
- Allocate your percentages. Assign each origin a number between 0 and 100, so the total hits exactly 100% [4].
- Account for weight loss. The 1kg bag price is based on green bean weight before roasting, not on what lands in your bag. You pay for 1kg of green beans either way; how much of that weight survives the roaster comes down to your crack choice, not which beans you picked [4][2].
This percentage-based system means you can build anything from a single-origin cup (100% of one bean) to a four-way blend.
Step 2: Pick the Crack, Choosing Your Roast Profile
After selecting your beans, you choose between two roast levels: 1st Crack or 2nd Crack [3][2]. The "crack" refers to audible sounds the beans make during roasting, as internal moisture escapes and the beans go through chemical change [5].
- 1st Crack. This happens between 180 to 205°C and gives a lighter roast. Beans at this stage keep higher acidity, brighter flavours, more of the origin character, and more of the original green weight, since less moisture has cooked off [5]. A fruit-forward, Colombia-heavy blend holds onto those notes best at 1st Crack.
- 2nd Crack. This happens at higher temperatures and pushes the cup toward darker, bolder, smokier flavours with lower acidity [5]. Roast character starts to dominate over origin flavour, and more moisture cooks off along the way, so the same beans come out lighter than a 1st Crack order.
- Match crack to blend. A nutty, Brazil Cerrado-heavy blend can shine at 2nd Crack, where the chocolate and roast notes deepen. A clean Mexico Altura blend is wasted under a dark roast; 1st Crack lets its subtlety through.
- Make your call. Pick 1st Crack or 2nd Crack when ordering. There's no middle option. Naki Roast keeps the choice binary, on purpose, to keep the experiment focused [3].
Your crack choice sets the flavour profile of your final cup, from bright and acidic to deep and smoky [5].
The Science Behind the Roast: What Happens to Your Beans
Understanding why your crack choice matters means knowing what happens inside the roaster. Roasting runs through three phases: drying, Maillard/pyrolysis, and cooling [6].
During drying, residual moisture evaporates from the green beans. The Maillard/pyrolysis phase is where the flavour gets made: heat drives chemical reactions between amino acids and sugars that build flavour compounds, colour, and aroma [6]. Both cracks happen inside this phase.
1st Crack happens early in the Maillard/pyrolysis phase, when beans expand and release steam with an audible pop. 2nd Crack comes later, when oils start migrating to the surface and the bean's cellular structure begins to fracture [5]. The further into this phase you push, the more roast character takes over from origin character.
The final phase, cooling, stops the reaction fast to lock in the profile you chose. That's why your crack choice has such a big effect on the cup: you're deciding how far into the chemical transformation you want your beans to go [6].
Lab Rat Pricing vs. Standard Naki Roast Bags
A custom 1kg Lab Rat bag costs NZ$60 [1][3]. For context, standard 250g bags from Naki Roast, like The Mule, run NZ$18 [1][7].
| Product | Weight | Price | Per-kilo equivalent |
|---|---|---|---|
| Lab Rat (custom) | 1kg (green weight) | NZ$60 | NZ$60 |
| The Mule (standard) | 250g | NZ$18 | NZ$72 |
Four standard 250g bags would run about NZ$72 at that per-gram rate. The Lab Rat bag comes in at NZ$60 for the same green weight: cheaper per kilo, and you get full say over blend and roast [1][7].
The trade-off: you're committing to a full kilo of one custom recipe, not sampling several pre-designed blends. For people who already know what they want, that's the point.
What You Get: Freshness and the Final Product
Your custom Lab Rat blend is roasted to order, not pulled off a shelf where it's been ageing [1][3]. Roast-to-order means every bag starts its life when your order does.
The final product ships in hand-stamped packaging, a small, tactile detail that reinforces the experimental, maker-driven identity of the product [1].
One note on what's in the bag: the 1kg weight is measured in green beans, before roasting, using the same beans regardless of crack choice [4]. What changes is how much of that weight survives the roast. 1st Crack drives off less moisture, so you keep more of it, closer to 900g roasted from a 1kg green order. Push to 2nd Crack and more moisture cooks away, closer to 850g. Neither figure is a rip-off; it's the roast doing its job. You're paying for green weight and flavour concentration, not a fixed roasted weight.
Frequently Asked Questions
How much coffee do I get from 1kg of green beans after roasting?
Less than 1kg of roasted coffee, and how much less depends on your crack choice, not on which beans you picked. The 1kg weight is measured in green beans, before roasting [4][2]. 1st Crack keeps more of that weight, since less moisture has cooked off; 2nd Crack drives off more, so you end up with less. It's a standard part of roasting: the bag is sold by green weight, and the flavour in your final product is concentrated.
What's the taste difference between 1st Crack and 2nd Crack?
A 1st Crack roast is lighter with higher acidity. A 2nd Crack roast is darker, bolder, and smokier with lower acidity [5]. Your choice sets the flavour profile, from bright and acidic to deep and smoky, based on the audible sounds that mark key chemical changes in the bean [3][2].
Does the price change depending on which beans I choose for my roast?
No. The Lab Rat custom roast is a flat NZ$60 for a 1kg bag [1][3]. That price holds regardless of which of the four origins you choose or the percentages you assign them.
What happens to the acidity if I choose a 2nd Crack roast?
It drops. A 2nd Crack roast pushes toward darker, bolder, smokier flavours, which comes with lower acidity than a lighter 1st Crack roast [5]. That choice directly shapes the final flavour profile of your custom blend.
Which bean origin suits a chocolatey, full-bodied custom roast?
Brazil Cerrado brings nutty and chocolate notes, a strong pick for a chocolatey profile [1]. For a full body, India Soft Touch brings low acidity and a heavy body [1]. Blend the two in your custom Lab Rat order to hit that specific flavour.
Sources
- nakiroast.co.nz: Lab Rat pricing, bean origins, and hand-stamped branding.
- nakiroast.co.nz: Experimental positioning of the Lab Rat service.
- nakiroast.co.nz: Roast-to-order process and "pick the crack" options.
- nakiroast.co.nz: Details on green bean weight loss during roasting.
- www.e-cafebank.com: Technical definitions of 1st and 2nd crack temperatures and sounds.
- www.eeca.govt.nz: Scientific phases of the coffee roasting process.
- nakiroast.co.nz: The Mule 250g pricing for per-kilo comparison.