What is Screen 18 Coffee?
Vietnamese Robusta Grading Explained
"Screen 18" appears on every Vietnam Robusta spec sheet — but buyers frequently confuse it with Grade 1, or assume Color Sorted and Cleaned are the same. This guide explains what the number means, why it matters, and how to write a correct purchase order.
What the Number Actually Means
Screen grading is purely mechanical. Green coffee beans are passed over a flat sieve with round holes of a fixed diameter. Beans that stay on top are "retained"; beans that fall through are "passed". The screen number is the hole diameter in 1/64 inch increments — an old US-origin convention still used globally.
The formula:
Screen number × (1/64 inch) = hole diameter in inches → convert to mm
Screen 18 = 18 × 1/64" = 0.28125" = 7.14 mm
| Screen | Hole Diameter | Min Retention | TCVN Grade | Typical Use |
|---|---|---|---|---|
| Screen 13 (S13) | 5.16 mm | ≥ 90% | G2 Underscreen | Robusta G2 small bean, lower-tier blends |
| Screen 16 (S16) | 6.35 mm | ≥ 90% | G1 S16 | Mid-range blends, espresso base |
| Screen 18 (S18) | 7.14 mm | ≥ 90% | G1 S18 | Premium blends, soluble, strong espresso |
Source: TCVN 4193:2014 — Vietnamese national standard for green coffee export quality.
Why Screen 18 Matters to Buyers
For green coffee buyers, screen size is an operational specification, not just a quality signal.
Roast Uniformity
Uniform bean size loads more evenly on the drum. Smaller beans roast faster than larger ones — mixed sizes produce uneven roast development. S18 minimises this variance.
Less Chaff
Larger, denser beans shed less silver skin during roasting. Lower chaff volume reduces roaster cleaning frequency and fire risk in continuous-roasting operations.
Soluble Extraction
Instant coffee manufacturers specify S18 for consistent grind particle distribution. Uniform bean size produces a more predictable grind profile and higher, more consistent extraction yield.
Grade Comparison: S18 vs S16 vs G2
All values from TCVN 4193:2014. S18 and S16 grades require ≥ 90% retention on the stated screen.
| Grade | Screen | Black | Broken | Foreign | Moisture | Typical Use |
|---|---|---|---|---|---|---|
| G1 S18 — Color Sorted | S18 (≥90% retention) | ≤ 0.2% | ≤ 0.5% | ≤ 0.1% | ≤ 12% | Soluble/instant, premium espresso blends |
| G1 S18 — Cleaned | S18 (≥90% retention) | ≤ 0.5% | ≤ 1% | ≤ 0.5% | ≤ 12.5% | Mainstream espresso, roast & ground blends |
| G1 S16 — Color Sorted | S16 (≥90% retention) | ≤ 0.2% | ≤ 0.5% | ≤ 0.1% | ≤ 12% | Blends requiring tight defect control, smaller bean |
| G1 S16 — Cleaned | S16 (≥90% retention) | ≤ 0.5% | ≤ 1% | ≤ 0.5% | ≤ 12.5% | Standard espresso blends, cost-sensitive buyers |
| G2 Standard (FAQ) | Mixed — no screen spec | ≤ 2% | ≤ 5% | ≤ 1% | ≤ 12.5% | Lower-tier blends, price-driven volume |
Highlighted rows = Screen 18 grades. Full spec documentation available on request.
5 Common Screen 18 Misunderstandings
These five misunderstandings appear repeatedly in RFQs and purchase orders from first-time Vietnam coffee buyers.
✗ ""Grade 1" means Screen 18"
Grade 1 (G1) is a quality classification — it tells you defect tolerances, not bean size. You must specify the screen separately. "G1 S18 Cleaned" and "G1 S16 Cleaned" are both Grade 1 but different sizes.
✗ ""Cleaned" and "Color Sorted" are the same"
Cleaned = screen grading + gravity table only. Color Sorted adds an optical/electronic pass that removes discoloured beans. Color Sorted achieves roughly half the defect tolerance of Cleaned — Black ≤0.2% vs ≤0.5%, Broken ≤0.5% vs ≤1%.
✗ ""Screen 18" means every bean is exactly 7.14 mm"
Screen 18 means ≥ 90% of beans are retained on a 7.14 mm round-hole sieve under TCVN 4193:2014. Up to 10% can pass through. Expect a natural distribution, not uniformity.
✗ ""FAQ grade" is a quality endorsement"
"FAQ" stands for Fairly Average Quality — it is the commercial name for Grade 2 Standard. It has no screen size requirement and significantly looser defect tolerances than G1.
✗ "Higher screen = better flavour"
For Robusta, larger screen size improves roast uniformity and reduces chaff — both operationally valuable. Flavour differences between S16 and S18 Robusta are marginal. The defect level (Black, Broken) has far more impact on cup quality.
How to Spec a Screen 18 Order
Use the full TCVN grade name on your purchase order. Ambiguous spec language is the most common cause of grade disputes on arrival.
Ambiguous (avoid)
- "Vietnam Robusta Grade 1"
- "Vietnam coffee S18"
- "Screen 18 cleaned coffee"
- "G1 coffee, Vietnam"
Precise (use this)
- "Vietnam Robusta G1 S18 Color Sorted, TCVN 4193:2014, Moisture ≤ 12%"
- "Vietnam Robusta G1 S18 Cleaned, TCVN 4193:2014, Moisture ≤ 12.5%"
- "SGS pre-shipment inspection required"
What to include in every RFQ:
- 1. Species (Robusta or Arabica)
- 2. Grade (G1 or G2)
- 3. Screen size (S16, S18, or no screen spec for G2)
- 4. Processing (Cleaned or Color Sorted)
- 5. Reference standard (TCVN 4193:2014)
- 6. Moisture limit (≤ 12% or ≤ 12.5%)
- 7. Third-party inspection requirement (SGS recommended)
Frequently Asked Questions
What does "Screen 18" mean in Vietnamese coffee?
Screen 18 refers to a physical sieve with 7.14 mm round holes. Under TCVN 4193:2014, a Screen 18 lot must retain ≥ 90% of beans on that sieve. It is a size classification, not a quality or flavour designation.
What is the difference between G1 S18 Cleaned and G1 S18 Color Sorted?
Both are Grade 1 Screen 18 lots but processed to different tolerances. Cleaned passes through screen grading and gravity table, achieving Black ≤ 0.5%, Broken ≤ 1%, Foreign Matter ≤ 0.5%. Color Sorted adds an optical sorting pass: Black ≤ 0.2%, Broken ≤ 0.5%, Foreign Matter ≤ 0.1%. Color Sorted is the tighter specification.
Why do soluble coffee manufacturers prefer Screen 18?
Larger, uniform beans load more evenly onto the roasting drum, reducing temperature variance across the batch. Consistent bean size produces a more even roast — important for soluble extraction yield and flavour consistency at scale.
What is the TCVN 4193:2014 standard?
TCVN 4193:2014 is the Vietnamese national standard for green coffee export quality, issued by the Ministry of Science and Technology. It defines screen size grades, defect classifications, moisture limits, and testing methods for commercial lots. All GreenTech export lots are graded to this standard.
Can I request a screen size that is not S16 or S18?
GreenTech primarily supplies S16 and S18 Robusta grades. S13 (Underscreen / small bean) is available as G2 grade. Custom screen specifications outside TCVN grades are possible for large-volume contracts — contact us to discuss.
How should I specify a Screen 18 order on my purchase order?
Use the full TCVN grade name: "Vietnam Robusta Grade 1 Screen 18 Color Sorted, TCVN 4193:2014" or "Vietnam Robusta G1 S18 Cleaned, TCVN 4193:2014". Include moisture limit (≤ 12% or ≤ 12.5% depending on grade) and request SGS pre-shipment inspection.
Ready to Source Screen 18 Robusta?
GreenTech supplies G1 S18 Cleaned and Color Sorted from Lam Dong and Dak Nong. SGS-inspected. ISO 22000 certified. GACC registered for China-bound shipments.
This guide reflects TCVN 4193:2014 grade definitions. Individual lots are SGS-inspected prior to shipment. Contact us for the current lot specification sheet.
