SL28 and SL34 are Kenya's signature cultivars, developed in the 1930s by Scott Laboratories for the Kenyan growing environment. Finding them blended with Ethiopian heirloom varieties in a Yirgacheffe lot is genuinely unusual — these two plant types bring fundamentally different chemistry to the same blend.
Kenyan SL cultivars are associated with phosphoric acid, which tastes noticeably different from the citric acid that drives most Ethiopian washed profiles. Where citric gives orange and lemon brightness, phosphoric produces a cola-like quality and mellows citrus toward a rounder, almost mango-adjacent character. Blending SL28 and SL34 into an Ethiopian heirloom base introduces that phosphoric dimension alongside the citric-dominant Ethiopian terroir character.
For a filter blend, this creates a useful complexity problem at extraction. The SL varieties and Ethiopian heirlooms have different physical properties — Ethiopian heirlooms grind harder and produce more fines, while SL cultivars are structurally distinct. When components have different extraction behaviors, the blend parameters represent a compromise: the setting that extracts the Ethiopian component optimally may under-extract the Kenyan varieties, and vice versa. This is the practical consequence of any blend flagged for compound origins.
The juicy berries and apricot notes map to the citric and malic acid interplay from the Ethiopian heirlooms. The hazelnuts are Maillard browning products — methylpropanal and 3-methylbutanal formed from valine and leucine respectively during light roasting. The creamy caramel is aroma-mediated sweetness: caramelization compounds like maltol and furanones that register as sweet even though actual sucrose is exhausted during roasting. The [washed processing](/blog/coffee-processing-methods-explained) keeps all of this clean — no natural fermentation funk to muddy the acid-forward structure.
The Ethiopian heirloom and light washed characteristics combine here to produce an unusually specific grind logic: the net adjustment is only 20μm finer than default (530μm) because Ethiopian heirloom fines — which Gagné documents as distinctively elevated in this variety group — actually assist extraction evenness through the Chemex's thick paper in a way coarser grinds don't. Elevated fines help paper filter extraction rather than hindering it. At 2,000m altitude — the highest among the origins in this blend — the Ethiopian heirloom component has extreme density and slow cherry maturation — meaning the soluble load per bean is high, but harder to access. The Chemex's long, slow drawdown through thick paper gives the brew the contact time it needs, producing the clearest possible expression of the juicy berry and apricot acids alongside the creamy caramel body.
Troubleshooting
sour: Grind finer by ~22μm and raise temp by 1°C. At 2,000m, these Ethiopian heirlooms are maximally dense — even with elevated fines, the Chemex under-extracts if grind is slightly coarse. Hazelnut and caramel extract in the middle dissolution phase and require both adequate temperature and surface area to appear.
thin: Add 1g dose or reduce water by 15g. Chemex strips oils from this lean light roast. Creamy caramel is aroma-mediated sweetness from furanones and maltol — if absent, TDS is too low and these volatiles aren't present in sufficient concentration. Dose is the first adjustment before anything else.
Ethiopian heirloom varieties in this Hey Buddy blend grind harder and more brittlely than most Arabica, producing elevated fines even at nominal medium-fine settings. The recipe accounts for this with a net 20μm coarser-than-pure-roast-adjustment grind (480μm), because the elevated fines from Ethiopian heirlooms already function like a finer grind in terms of hydraulic resistance and extraction rate. The SL28 and SL34 component adds a wrinkle: Kenya's Scott Labs varieties are physically distinct from Ethiopian heirlooms and may produce different particle size distributions at the same grind setting, creating a blend that requires a compromise grind. At 94°C, the recipe targets the light roast's extraction demands — the juicy berries and apricot notes from heirloom citric and malic acids need sufficient temperature to extract into the caramel and hazelnut base.
Troubleshooting
sour: Grind finer by ~22μm and raise temp by 1°C. The SL28-SL34 component of this blend extracts differently from the Ethiopian heirloom base — if the grind is optimized for heirlooms but slightly coarse for the Kenyan varieties, the result is a citrus-dominant, sour cup. Finer grind closes that extraction gap.
thin: Add 1g dose or reduce water by 15g. Ethiopian heirloom fines improve extraction efficiency but don't increase soluble mass — at light roast, TDS runs lean regardless. If hazelnut and creamy caramel are absent, increase dose; a metal filter recovers oils the V60 paper strips from this blend.
The Kalita Wave at 510μm benefits this SL28-SL34-heirloom blend specifically because of the flat bed's even saturation — Ethiopian heirloom fines behavior is especially relevant here. The central challenge with this three-variety blend is that Ethiopian heirlooms and SL cultivars have different hydraulic resistance at the same nominal grind size: heirlooms produce more fines (higher fine-particle resistance) while SL28's larger beans grind more evenly. A conical dripper would allow faster drainage paths to form around the coarser SL particles, creating uneven extraction. The Kalita Wave's flat bed prevents this by maintaining consistent water depth across the full puck surface, ensuring both variety components extract evenly at 94°C. The hazelnut and caramel notes — which are Maillard products from light roasting — need this even extraction to emerge alongside the juicy berry brightness.
Troubleshooting
sour: Grind finer by ~22μm and raise temp by 1°C. SL28's larger, denser beans resist extraction at parameters optimized for finer Ethiopian heirlooms. If berry and apricot dominate without caramel support, finer grind increases resistance from the heirloom fines, slowing SL particle drainage so both components extract fully.
thin: Add 1g dose or reduce water by 15g. The Kalita paper is less aggressive than Chemex at oil removal, but body can still be absent — the 2,000m heirloom's light-roast solubility is limiting extraction. Increase dose rather than adjusting grind; grind already compensates for this multi-variety blend.
AeroPress at 380μm — only 20μm finer than the default rather than the full light-roast adjustment — reflects the Ethiopian heirloom varieties' elevated fines contribution: when grinding heirloom beans, the natural fines fraction already increases effective extraction, so the grind doesn't need to move as far. The juicy berries and apricot notes respond well to the AeroPress's short, intense extraction because citric and malic acids are fast-phase compounds that exit early in the dissolution curve. The hazelnut and creamy caramel notes, being Maillard products, require the fine grind and full 1–2 minute steep to follow. The closed chamber keeps volatile aromatics locked in the brew rather than escaping as they would in an open pour-over. The 1:12–1:13 concentrate ratio amplifies all four flavor notes.
Troubleshooting
sour: Grind finer by ~22μm and raise temp by 1°C. The AeroPress extracts the SL28 phosphoric acid dimension quickly — that cola-like brightness can dominate if extraction stops before the hazelnut Maillard compounds appear. Finer grind plus slightly higher temperature push the extraction window past the acid-only phase.
thin: Add 1g dose or reduce water by 15g. Ethiopian heirloom fines can clog the AeroPress paper, causing channeling — if the press feels unusually easy and the cup is weak, fines are bypassing the filter. Extend steep to 1:30 before pressing; switch to a metal filter if thinness persists.
Clever Dripper at 82/100 for this blend benefits from the same logic as the Kalita — flat-bottom drawdown produces even extraction across the multi-variety puck — while adding immersion's benefit of extended contact time at full temperature. The 510μm grind accounts for the Ethiopian heirloom's elevated fines contribution. During the 3–4 minute immersion phase at 94°C, the slow-diffusing Maillard compounds from this 2,000m high-altitude light roast have time to enter solution: the hazelnut and creamy caramel notes require this sustained contact, unlike the juicy berries and apricot acids which would be fully extracted within the first minute. The paper filter's drawdown phase then delivers clarity comparable to pour-over, making the Clever Dripper an excellent method for this blend when the brewer wants less technique involvement than V60 but more clarity than French press.
Troubleshooting
sour: Grind finer by ~22μm and raise temp by 1°C. If the Clever Dripper leads with sharp berry acidity without creamy caramel rounding, the Maillard compounds didn't fully extract during steep. Finer grind and higher temperature accelerate the middle phase — keep the lid on to maintain brew temperature throughout.
thin: Add 1g dose or reduce water by 15g. Ethiopian heirloom at 2,000m is extremely dense — even elevated fines can't overcome light roast solubility limits in the Clever's immersion phase. If hazelnut and caramel are absent, increase dose first; extend steep to 4 minutes as the secondary adjustment.
Light-roast Ethiopian heirloom espresso creates the most involved adjustment for this blend. The net grind is 230μm — the 40μm light-roast reduction partially offset by the 10μm coarser adjustment for Ethiopian heirloom fines management. Ethiopian heirlooms at espresso grind produce elevated fines that increase puck resistance dramatically; without the coarser offset, the shot would stall or channel. At 93°C and 1:1.9–1:2.9 ratio, this is deliberately a longer, slightly cooler espresso to extract through the heirloom-SL28 blend's light-roast density. Pre-infusion is essential: the blend's variety mixture creates a heterogeneous puck where the larger SL28 beans and finer heirloom particles need different wetting times. Expect the phosphoric acid from SL28 and SL34 to produce a distinctive cola-brightness in the finish — unlike straight Ethiopian espressos.
Troubleshooting
sour: Grind finer by ~10μm and raise temp by 1°C. Light roast espresso with this three-variety blend sits right at the extraction boundary — the SL28 component's dense large beans resist extraction, and the shot exits before caramel sweetness appears. Even 10μm tighter grind significantly raises resistance and extends extraction time.
thin: Add 1g dose or reduce output by 15g. The 1:1.9–1:2.9 ratio already compensates for light-roast solubility — if the shot is still thin and hazelnut absent, increase dose. Avoid shortening the ratio; a tighter pull increases sour character before it increases body with this heirloom-SL blend.
Ethiopian heirloom fines behavior matters for the moka pot, and the interaction is specific: Ethiopian heirloom fines at moka pot's medium-fine grind (330μm) can potentially over-pack the basket, increasing pressure beyond the pot's design spec. The recipe stops 10μm coarser than a pure roast-adjustment would suggest to prevent this. Pre-boiling the base water is critical here — the Ethiopian heirloom component at 2,000m altitude has volatile aromatic precursors (the jasmine and bergamot-adjacent floral notes from high-altitude slow maturation) that are destroyed by steam exposure before brewing properly begins. Cold-start moka pots with light roast lose these aromatics before extraction even begins. At 100°C, the boiling start temperature drives maximum extraction through the 330μm grind, which should produce the juicy berry concentration and apricot character in the concentrated moka pot output.
Troubleshooting
sour: Grind finer by ~22μm and use pre-boiled water. Moka pot sour with this Ethiopian-SL blend means steam is extracting only fast-phase acids before boiling pressure builds. Pre-boiled water and medium heat prevents the steam-first pattern that strips hazelnut and caramel character before proper extraction begins.
thin: Add 1g dose or reduce water by 15g. High solubility potential at 2,000m doesn't help if moka pot's 1.5-bar pressure can't access it. If the concentrated output feels watery, dose is limiting — increase dose before touching grind to avoid packing the basket too tightly with elevated heirloom fines.
strong: Reduce dose by 1g or increase water by 15g. Ethiopian heirloom fines can increase extraction efficiency beyond what the recipe predicts — if the output is intensely concentrated past drinking strength, reducing basket dose is more reliable than diluting an already-brewed concentrate with plain water.
French press at 980μm is the coarsest grind for this blend, and the Ethiopian heirloom fines profile adds a useful counterpoint: even at this coarse setting, Ethiopian heirloom fines will be present in the cup after pressing. French press doesn't truly filter — the metal mesh holds back boulders but allows fines and oils through freely. For a light-roast blend at 2,000m altitude, those heirloom fines contribute to body and extraction evenness in ways that are muted by paper filters in other methods. The unfiltered output means the SL28 and SL34's distinctive brightness character — the cola-like brightness that distinguishes this blend from straight Ethiopian lots — is present alongside the malic and citric acids without the taming effect of paper. At 96°C, the coarse immersion grind gets the maximum thermal driving force for diffusion extraction over the 4–8 minute window.
Troubleshooting
sour: Grind finer by ~22μm and raise temp by 1°C. French press at 980μm walks the under-extraction line for this light roast — heirloom fines help, but if the coarse fraction is too large, hazelnut and caramel never appear. Extend steep to 6 minutes before touching grind.
thin: Add 1g dose or reduce water by 15g. SL28 and SL34 are larger-beaned than the heirloom varieties — at 980μm, those larger beans may be under-extracted, dragging down total TDS. Increasing dose is more direct than adjusting grind when the issue is concentration rather than acid-sweetness balance.
Cold BrewFlash Brew Recommended
Cold brew is not recommended for this bean. At near-freezing temperatures, cold water cannot extract the complex acids, delicate aromatics, and bright fruit compounds that define a light-roasted coffee — they remain locked in the cell matrix. For a cold version of this coffee, use flash brew: brew a concentrated pour-over (V60 or Chemex at 60% of the normal water volume) directly over ice in the server. The hot water extracts the full flavor spectrum, and the rapid ice cooling locks in volatiles that would otherwise evaporate during a slow cool-down.