The stone mortar predates the Thai kitchen by millennia — it is among the oldest of all culinary tools across Southeast Asia, South Asia, and the Mediterranean. In Thailand, the khrok (mortar) and saak (pestle) sit beside every domestic stove and every street food cart. Thompson is explicit in his insistence on the mortar: it is not a preference or a concession to tradition — it is a requirement for the preparations he describes.
The granite mortar and its wooden or granite pestle are not equipment — they are the Thai kitchen's defining instrument, and the quality of every curry paste, every relish, every pounded salad depends entirely on the understanding of how to use them. The mortar pounds; it does not blend. The distinction is not semantic: blending chops and emulsifies; pounding crushes, ruptures, and integrates at a cellular level. A paste made in a food processor and a paste made in a mortar are made from the same ingredients and are not the same preparation. The cell walls of lemongrass, galangal, and kaffir lime are ruptured differently by a descending weight than by a spinning blade — the aromatics released, the texture produced, and the depth of flavour achieved are categorically different results.
As Segnit notes, lemongrass and galangal occupy overlapping but distinct aromatic territories: lemongrass's citral dominates the top aromatic register (fresh, citrus, bright), while galangal's galangin and related diarylheptanoids occupy the deeper, more resinous register. When pounded together in a mortar, these compounds interact within the paste rather than sitting as separate aromatic layers — the cell rupture releases them simultaneously into the surrounding paste mass where they bind with the fat of the shrimp paste and the chilli's capsaicin-carrier oils. This integration is the reason Thompson's pastes taste deeper and more complete than commercial or blended versions: the aromatics are bound into the paste's fat phase rather than sitting as discrete top notes.
**The two mortars of the Thai kitchen:** - The heavy granite mortar (khrok hin): for curry pastes and wet relishes — its weight and hardness handle the woody fibres of lemongrass, galangal, and hard spices. The granite's slightly porous surface grips the paste material and creates friction that contributes to the pounding action. 24–28cm diameter minimum for curry paste work; smaller mortars require the work to be done in batches. - The clay or ceramic mortar (khrok din): for som tam (green papaya salad) — lighter, its internal surface releases rather than grips, appropriate for bruising the vegetables gently rather than pulverising them. **The sequence of pounding — paste construction order:** This sequence is where the dish lives or dies. The logic is hardness: always pound the hardest, driest ingredients first, then add progressively softer and wetter ones. Dry spices and chillies (toasted, dried) before lemongrass before galangal before fresh chilli before shrimp paste. Each ingredient is pounded to a rough paste before the next is added. Adding a wet ingredient before the dry is fully reduced produces a paste that never fully integrates — the moisture from the wet ingredient cushions the impact of the pestle on the remaining dry fibres. **Standard curry paste sequence:** 1. Dried chillies (soaked, drained, roughly chopped) — pounded first, alone, to a rough mass. 2. Dry spices if used (coriander seed, cumin, white peppercorns — toasted and ground separately first, then added). 3. Salt (a pinch — acts as an abrasive). 4. Lemongrass (white stalk only, sliced thin). 5. Galangal (peeled, sliced thin). 6. Kaffir lime zest. 7. Coriander root (scraped clean — not coriander leaf, not coriander stem: specifically the root and its attached lower stem, with a flavour entirely different from the leaf). 8. Garlic. 9. Shallots. 10. Shrimp paste (kapi) — last, because its moisture and fermented character change the texture of the paste from the moment of addition. **The test of a correct paste:** A small amount of the finished paste rubbed between thumb and forefinger: no fibrous strands should be detectable. A fibre-free paste requires 20–30 minutes of continuous pounding for most curry pastes. Thompson does not hedge on this time. Decisive moment: The transition from 'rough paste with visible fibrous texture' to 'smooth, integrated paste with no detectable strands.' This transition happens gradually across the pounding time and is assessed by the fingertip rub test throughout. Once it is smooth, stop — further pounding begins to aerate the paste and changes its texture to something less dense. The moment of completion is when the rub test between thumb and forefinger returns no fibrous resistance — only the fine grit of well-pounded dry ingredients integrated into a smooth paste of even colour. Sensory tests: **Feel — the rub test (conducted throughout):** Pinch a small amount of the working paste between thumb and forefinger and rub in a circular motion. At 10 minutes: coarse fibre clearly detectable. At 20 minutes: finer, but threads still perceptible. At 30 minutes: the paste between the fingers feels smooth and homogeneous — the fibre test returns clean. This is the standard and the goal. **Smell — the aromatic release:** The transformation of the mortar's smell during pounding is one of the most dramatic of all kitchen sensory experiences. At the beginning: the chillies' dry heat and the separate, discernible smell of each ingredient. As the lemongrass cell walls rupture under pounding: an immediate, intense release of lemongrass's citral compounds — fresh, bright, citrus-herbal. As galangal integrates: a deeper, more resinous note below the citrus. As shrimp paste enters: the earthy, fermented, sea-floor depth that anchors the aromatics and provides the paste's foundation. **Sight — the integrated paste:** Correctly pounded paste is smooth, deep in colour (from the chilli's carotenoids and the shrimp paste's deep, dark fermented colour), slightly sticky, and cohesive — it holds together when a spoon is drawn through it and does not separate back into visible components.
- Pound in a steady, rotational rhythm — rotating the mortar occasionally so the paste accumulates evenly and every part receives equal pestle impact - A damp cloth under the mortar prevents it from skating on the bench under the impact of vigorous pounding - Finished paste can be refrigerated for up to 5 days in an airtight container — the flavour deepens after 24 hours as the aromatics continue to integrate
— **Food processor paste:** The blades shear the fibres at a different angle than a descending weight. The result: a paste of correct flavour components that lacks the integration and depth of a pounded paste. The fibres are cut, not crushed; the cell walls are not ruptured — the aromatic oils remain inside the cells rather than being released into the paste mass. Thompson is unequivocal: the food processor is a substitute, not an equivalent. — **Wet paste that never smooths:** Wet ingredients (shallots, fresh chilli) were added before the dry and woody ingredients were fully reduced. The wet cushions the pestle impact and prevents the fibrous reduction of the woody material. Restart in correct sequence. — **Lumpy, uneven paste with visible herb fibres:** Insufficient pounding time. Return to the mortar and continue. There is no shortcut to the 20–30 minute standard for a true curry paste.
David Thompson, *Thai Food* (2002); *Thai Street Food* (2010)