LNB42
LNB42 polyurethane hardener (Milesi)
Milesi polyurethane (isocyanate) hardener — the second component for two-pack PU sealers and lacquers. The dealer lists it as a 'hardener for PU primers and matt lacquers'. It has no page of its own on the Technocolor site, but it is named on the official pages for the LBA42 universal sealer (the only hardener), the LBR21811 MDF isolating primer (40 %), the LGA21 40-gloss lacquer, the LGA531–536 thixotropic lacquers and the LGA84 polyvalent lacquer — almost always 50 % by weight (1 : 0.5, i.e. 2 parts base to 1 part hardener). According to Milesi's US distributor, LNB42 dries faster and gives a harder but more brittle and more yellowing film than LNB20, and isn't recommended in systems of more than three coats. Don't use it under whites or pale non-yellowing finishes.
- LBA42 universal PU sealer — 50 % by weight / 50 % by volume (the only hardener)
- LBR21811 PU isolating primer for MDF — 40 % by weight / 45 % by volume (or LNB77)
- LGA21 PU lacquer 40 gloss — 50 / 50 % (or LNB77)
- LGA531–536 thixotropic PU lacquers 65…3 gloss — 50 / 50 % (or LNB77/LNB5)
- LGA84 polyvalent PU lacquer 20 gloss — 50 / 50 % (or LNB21)
- per Milesi dealers / TDS abroad — LBA521, LBA26, LBA45 (50 %)
Ask about LNB42
Answers are based on the LNB42 data and the products it mixes with.
Mixing matrix
- LBA42base% by weight: 50 %official% by volume: 50 %official
Universal PU sealer — LNB42 is the only listed hardener.
- LBR21811base% by weight: 40 %official% by volume: 45 %official
PU isolating primer for MDF — alternative to LNB77. Note it's 40 % by weight here (45 % by volume), not 50.
- LGA21base% by weight: 50 %official% by volume: 50 %official
PU lacquer 40 gloss (spray and curtain) — alternative to LNB77; handy if you keep one hardener for the LBA42 sealer and the topcoat.
- % by weight: 50 %official% by volume: 50 %official
Thixotropic PU lacquers LGA531–536 (65/45/30/20/10/3 gloss), spray and electrostatic — LNB42 is listed first, on a par with LNB77 and LNB5.
- LGA531base% by weight: 50 %dealer
Hungarian Milesi distributor variant: 50–60 % LNB42 (the main hardener), with LNB05/42A/77/190/111 also allowed. The page is titled LGA 531 but describes a 45-gloss lacquer — treat as a pointer, not a recipe; Technocolor says 50 % flat.
- LGA84base% by weight: 50 %official% by volume: 50 %official
Polyvalent PU lacquer 20 gloss — alternative to LNB21. Per the Milesi TDS (as transcribed by a dealer), 50 % LNB42 gives more film build at the cost of slightly slower drying.
- LBA521base% by weight: 50 %dealer
Thixotropic PU sealer LBA521 — per the Belarusian Milesi dealer (2021). Technocolor currently lists LNB5/LNB77 for LBA521; use LNB42 only if you already have it and your supplier confirms.
- LBA45base% by weight: 50 %datasheet% by volume: 50.9 %datasheet
Milesi LBA45 clear PU sealer (US; not sold by Technocolor) — the TDS gives 50 % by weight / 50.9 % by volume, with LNB17 and LNB20 at the same 50 %. Listed for comparison only.
- LBA26base% by weight: 50 %dealer
Milesi LBA26 clear PU sealer (Pro Wood procedure, US) — LNB42 or LNB20 depending on the properties you want; mix viscosity 18 s Ford 4, pot life 3 h. Listed for comparison only.
| Role | Material | % by weight | % by volume | When |
|---|---|---|---|---|
| base | LBA42 | 50 %official | 50 %official | Universal PU sealer — LNB42 is the only listed hardener. |
| base | LBR21811 | 40 %official | 45 %official | PU isolating primer for MDF — alternative to LNB77. Note it's 40 % by weight here (45 % by volume), not 50. |
| base | LGA21 | 50 %official | 50 %official | PU lacquer 40 gloss (spray and curtain) — alternative to LNB77; handy if you keep one hardener for the LBA42 sealer and the topcoat. |
| base | LGA531 / LGA532 / LGA533 / LGA534 / LGA535 / LGA536 | 50 %official | 50 %official | Thixotropic PU lacquers LGA531–536 (65/45/30/20/10/3 gloss), spray and electrostatic — LNB42 is listed first, on a par with LNB77 and LNB5. |
| base | LGA531 | 50 %dealer | — | Hungarian Milesi distributor variant: 50–60 % LNB42 (the main hardener), with LNB05/42A/77/190/111 also allowed. The page is titled LGA 531 but describes a 45-gloss lacquer — treat as a pointer, not a recipe; Technocolor says 50 % flat. |
| base | LGA84 | 50 %official | 50 %official | Polyvalent PU lacquer 20 gloss — alternative to LNB21. Per the Milesi TDS (as transcribed by a dealer), 50 % LNB42 gives more film build at the cost of slightly slower drying. |
| base | LBA521 | 50 %dealer | — | Thixotropic PU sealer LBA521 — per the Belarusian Milesi dealer (2021). Technocolor currently lists LNB5/LNB77 for LBA521; use LNB42 only if you already have it and your supplier confirms. |
| base | LBA45 | 50 %datasheet | 50.9 %datasheet | Milesi LBA45 clear PU sealer (US; not sold by Technocolor) — the TDS gives 50 % by weight / 50.9 % by volume, with LNB17 and LNB20 at the same 50 %. Listed for comparison only. |
| base | LBA26 | 50 %dealer | — | Milesi LBA26 clear PU sealer (Pro Wood procedure, US) — LNB42 or LNB20 depending on the properties you want; mix viscosity 18 s Ford 4, pot life 3 h. Listed for comparison only. |
Percentages are per 100 parts of component A.
Characteristics
- Solids
- 26.6 ± 2 % by weight (hardener itself)datasheet
- Density
- 0.975 ± 0.030 kg/ldatasheet
- Chemistry
- isocyanate (NCO) hardener for 2K polyurethane ('Induritore poliuretanico')datasheet
- Pot life
- 3–4 h at 20 °C (of the mix)datasheet
- Drying · Conditions
- 18–22 °C, 65–70 % RH (Milesi standard)
- Drying · Dust-free
- 10–45dealer
- Drying · Touch-dry
- 45–90dealer
- Drying · Sand or stack
- LBA26 sealer: sand after ≥ 2 h (4 h better); LBA45 sealer: sandable / overcoatable after 24 h, recoat wet-on-wet 2–3 h without sandingdealer
- Drying · Full cure
- 4–24dealer
- Drying · Relative speed
- faster drying than LNB20dealer
- Drying · In LGA84 vs standard
- 50 % LNB42 increases film build at the cost of slightly longer drying (vs the standard catalyst); 50 % LNB77 instead gives more elasticity and a few units less sheendealer
- Hardness
- harder film than LNB20dealer
- Elasticity
- more brittle than LNB20 — not recommended in systems needing more than 3 total coatsdealer
- Lightfastness
- more yellowing than LNB20 (aromatic-type); for pale woods/whites use LNB190 or LNB20dealer
- Moisture sensitivity
- Isocyanate hardeners are sensitive to water.official
Application
Conventional spray
- Nozzle
- 1.8–2.1dealer
- Pressure · Printed
- 2.1–2.8 bardealer
LNB42 is never sprayed on its own — tip and pressure follow the mix. 1.7–1.8 mm is plenty for the thinner lacquers (LGA21, LGA53x); 1.8–2.0 mm for the LBA42/LBR21811 sealers.
HVLP
- Nozzle · Lacquer mix
- 1.5–1.7
- Nozzle · Sealer mix
- 1.7–2
- Nozzle · Why ru
- Отдельно не распыляется — по основному продукту. Финишные LGA21/LGA53x наносятся 80–140 г/м² при умеренной вязкости и хорошо распыляются HVLP 1,5–1,7 мм; LBA42/LBR21811 — шлифуемые изолирующие грунты с высоким сухим остатком (120–150 г/м²), им нужно 1,7–2,0 мм, что соответствует диапазону 1,8–2,1 мм для пневматики, который Pro Wood даёт для прозрачных ПУ Milesi.
- Pressure · air · Inlet pressure, min
- 2
- Pressure · air · Inlet pressure, max
- 2.2
- Pressure · air · at the cap, max
- 0.7
- Pressure · air · Why ru
- Стандартная настройка HVLP (давление на входе при нажатом курке, ≤ 0,7 бар на воздушной головке), как в практике мастерской владельца.
- Consumption
- 80–150official
Airmix (air-assisted airless)
- Nozzle
- 0.23–0.28dealer
- Pressure · fluid
- 41–62dealer
- Pressure · air
- 1–1.4dealer
Technocolor methods page: airmix is better suited to finish coats than airless.
Airless
- Nozzle
- 0.23–0.28dealer
- Pressure · fluid
- 124–145dealer
Better for the sealers (LBA42, LBR21811) than for topcoats.
Electrostatic
- Nozzle
- as airmix (09–11 thou)recommended
Curtain coater
LGA21 (120–140 g/m²) and LGA84 (140 g/m²) can be curtain-coated (official). Thin no more than 10 % for curtain — per the Milesi LGA83/84 TDS (dealer transcription); no separate figure for LGA21.
Process and compatibility
- Mixing
- Stir the base well, weigh LNB42 in exactly (usually 50 %, 40 % for LBR21811), stir, then thin. Thinner is calculated on part A only.dealer
- System limit
- not recommended in systems that require more than 3 total coatsdealer
- Temperature and humidity
- store 0–35 °C; apply 15–30 °C, optimum 18–22 °C at 65–70 % RH; do not dry below 15 °C; RH during drying 50–70 %; support moisture 8–14 %datasheet
- Don'ts
- don't eyeball it — weigh it
- don't leave the can open: isocyanate reacts with air moisture, goes cloudy and thickens
- don't use hardener that has gone cloudy or thick
- don't use LNB42 under whites or pale non-yellowing finishes — use LNB190/LNB20 or an acrylic
- don't build more than three coats on an LNB42 system — the film gets brittle
- don't mix with acrylic (AC) or other hardener families
- don't use the mix past its pot life
- don't spray below 15 °C or above 30 °C
Storage
- Shelf life
- 12 months from production datedatasheet
- Storage temperature
- 0–35 °C, closed, ventilated, out of direct sundatasheet
- Packaging
- 2.5 l, 12.5 l, 25 ldealer
Safety: Solvent-borne isocyanate hardener: highly flammable, and isocyanate vapour/mist is a respiratory sensitiser. Spray booth, A2/P2 respirator or air-fed mask, nitrile gloves, goggles, spark-proof equipment, no smoking. Decant only into polyethylene or stainless containers. See the LNB42 SDS.
Mixed into
LBA42 / LBA521 / LBA528 / LBR21811 / LGA21 / LGA531 / LGA532 / LGA533 / LGA534 / LGA535 / LGA536 / LGA6AB14 / LGA6AB16 / LGA84
Sources
Value tags: “official”, “dealer”, “catalog”, “schedule” are Technocolor data; “workshop” is from our own datasheets; “recommended” is our engineering estimate (hover to see the reasoning).
- Milesi/IVM 'Scheda Tecnica' LNB42 (IT, rev.1 2016-02): polyurethane hardener; density 0.975 ± 0.030 kg/l (8.1 lb/gal), solids 26.6 ± 2 %, shelf life 12 months; storage/application conditions
- Хольцком (timb.ru) LNB42 card: 'hardener for PU primers and matt lacquers', 2nd component for PU materials, solids 29 ± 1 %, 2.5/12.5/25 l
- t-colormarket.ru search — no LNB42 product (checked 2026-10-04)
- Official LBA42: LNB42 50 % w/v, LZC1026/LZC8643 10–30 %
- Official LBR21811: LNB77/LNB42 40 % w / 45 % v, LZC1026/LZC1051/LZC8643 10–40 % w / 15–50 % v
- Official LGA21: LNB77/LNB42 50 % w/v, LZC1051 10–30 %
- Official LGA531–536 (one page per gloss): LNB42/LNB77/LNB5 50 % w/v, S50/S70/S80 10–30 %
- Official LGA84: LNB21/LNB42 50 % w/v, LZC1026 10–30 %
- Хольцком LGA531: LNB42/LNB77 50/50
- milesi.hu LGA53x: LNB42 50–60 %, alternatives LNB05/42A/77/190/111; dust 10–15 min, touch 45 min, hard 4 h; ≥ 1.7 mm
- Ukrainian dealer transcription of Milesi LGA83/LGA84 TDS: 50 % LNB-42 → more film build, slightly slower drying; 50 % LNB77 → more elastic, a few units less sheen; ≤ 10 % thinner for curtain
- Belarusian Milesi dealer LBA521: LNB42 50 %, LZC1026 25 %
Not covered by the sources
- No official t-color.ru page for LNB42 and not sold on t-colormarket.ru (search empty, product URL 404)
- Not in the Technocolor 2025–2026 catalogue transcripts and not used in any official finishing schedule (information/technology)
- Milesi TDS gives only density, solids and shelf life — no viscosity, NCO content, colour or isocyanate type
- Solids conflict: Milesi TDS 26.6 ± 2 % vs Хольцком 29 ± 1 %
- Pot life / drying with LNB42 published only for sister Milesi products (LBA45, LBA26) and a mislabelled milesi.hu LGA53x page — none for LBA42, LBR21811, LGA21, LGA84 with LNB42
- No LNB42 SDS found
- HVLP settings derived (only conventional/airless/airmix from Pro Wood)
- milesi.hu allows 50–60 % LNB42 on LGA53x; Technocolor states 50 % flat — unclear whether the range applies to Russian-market product
- Pro Wood conventional-spray 30–40 psi is printed in the product-pressure column (atomisation column blank) — interpreted as air pressure
- LBA45 TDS shows identical drying for LNB42/LNB17/LNB20, contradicting Pro Wood's 'LNB42 dries faster'