LBA42
LBA42 universal 2K polyurethane primer/sealer
General-purpose two-pack polyurethane primer/sealer (hardener LNB42 at 2:1 by weight). Per the maker: high solids, good sag resistance, fast drying, and it sands very well both by hand and on automatic sanders. Spray-applied at 120–150 g/m² per coat.
- priming furniture, cabinet doors, interior doors and mouldings under PU lacquers/enamels
- building film on solid wood and veneer before the topcoat
- primer coats that will be sanded by hand or on a wide-belt/automatic sander
Mix calculator
Ask about LBA42
Answers are based on the LBA42 data and the products it mixes with.
Mixing matrix
- LNB42Hardener% by weight: 50 %official% by volume: 50 %official
Always. Fixed ratio — don't eyeball it.
LNB42 is moisture-sensitive — close the can straight away. LNB42 itself is ~26.5 % solids, ~0.98 kg/l (Milesi TDS for LBA45). For Milesi LBA45, 50 % w/w = 50.9 % v/v; Technocolor rounds it to 50 %.
- LZC1026Thinner% by weight: 10–30 (typ. 20) %official% by volume: 10–30 (typ. 20) %official
Default fast PU thinner for normal 18–22 °C shop conditions. 10–15 % for max build on verticals; 20 % standard; 25–30 % for the first coat on open-pored timber (oak, ash, mahogany) so it wets into the pores.
If you get poor flow-out or bubbles/pinholes it's almost always a thinning issue — add more thinner first, go slower second.
- LZC8643Thinner% by weight: 10–30 %official% by volume: 10–30 %official
Slow thinner — hot shop (above ~25 °C), big flat panels, or when the primer goes on dry/pops.
More open time for flow, but more dust pick-up and more sag risk on verticals.
| Role | Material | % by weight | % by volume | When |
|---|---|---|---|---|
| Hardener | LNB42 | 50 %official | 50 %official | Always. Fixed ratio — don't eyeball it.LNB42 is moisture-sensitive — close the can straight away. LNB42 itself is ~26.5 % solids, ~0.98 kg/l (Milesi TDS for LBA45). For Milesi LBA45, 50 % w/w = 50.9 % v/v; Technocolor rounds it to 50 %. |
| Thinner | LZC1026 | 10–30 (typ. 20) %official | 10–30 (typ. 20) %official | Default fast PU thinner for normal 18–22 °C shop conditions. 10–15 % for max build on verticals; 20 % standard; 25–30 % for the first coat on open-pored timber (oak, ash, mahogany) so it wets into the pores.If you get poor flow-out or bubbles/pinholes it's almost always a thinning issue — add more thinner first, go slower second. |
| Thinner | LZC8643 | 10–30 %official | 10–30 %official | Slow thinner — hot shop (above ~25 °C), big flat panels, or when the primer goes on dry/pops.More open time for flow, but more dust pick-up and more sag risk on verticals. |
Percentages are per 100 parts of component A.
Characteristics
- Properties (official)
- High solids; Good sag resistance; Fast drying; Excellent hand and machine sandabilityofficial
- Solids
- 45–52 % (part A, by weight)recommended
- Ready-mix solids %
- 38–45 % (A + LNB42, before thinning)recommended
- Viscosity · Ready to spray
- 16–20 s, DIN4/Ford4 cuprecommended
- Density
- 0.97–1.03 kg/l (part A)recommended
- Pot life
- 3–4 h at 20 °Crecommended
- Drying · Dust-free
- 30–45 minrecommended
- Drying · Touch-dry
- 60–90 minrecommended
- Drying · Sand or stack
- 2–4 h (hand sanding); overnight for machine sandingrecommended
- Drying · Recoat wet-on-wet (h)
- 1–2 h, no sandingrecommended
- Drying · Full cure
- 24 hrecommended
- Drying · Conditions
- 20 °C, 65–70 % RH
- Thixotropy
- Good sag resistance; not sold as a thixotropic primer (Technocolor's thixotropic PU primers are LBA521/LBA528)recommended
- Hardness
- hard, brittle-ish film with LNB42recommended
- Lightfastness
- will amber/yellow over time (aromatic PU + LNB42)recommended
- Elasticity
- moderate–low with LNB42recommended
Colours
- LBA42 · clear (assumed)
Application
HVLP
- Nozzle
- 1.7–2 mmrecommended
- Pressure · air
- 1.8–2.2 bar at gun inlet (trigger pulled), ≤0.7 bar at caprecommended
- Spray viscosity
- 16–20 s DIN4recommended
- Consumption
- 120–150 g/m² per coatofficial
- Wet film
- 120–155 µmrecommended
- Coats
- 1–2 coatsrecommended
- Flash-off
- 10–20 min between wet-on-wet passesrecommended
- Recoat
- 1–2 h wet-on-wet without sanding; else ≥4 h + sand P320recommended
- Sanding between coats
- 320–400 gritrecommended
Spray is the only method listed officially. 15–20 cm gun distance, 50 % overlap.
Conventional spray
- Nozzle
- 1.8–2.1 mm (0.070–0.086")dealer
- Pressure · fluid
- 2–2.8 bar (30–40 psi product pressure, pressure-pot feed)dealer
- Pressure · air
- 3–4 bar at gunrecommended
- Spray viscosity
- 16–20 s DIN4recommended
- Consumption
- 120–150 g/m² per coatofficial
Airmix (air-assisted airless)
- Nozzle
- 0.23–0.28 mm (0.009–0.011" tip)dealer
- Pressure · fluid
- 41–62 bar (600–900 psi)dealer
- Pressure · air
- 1–1.4 bar (15–20 psi)dealer
- Spray viscosity
- 18–25 s DIN4recommended
- Consumption
- 120–150 g/m² per coatofficial
Good option for production priming of doors/fronts: high transfer efficiency, little overspray. Technocolor's methods page rates Airmix as better suited to topcoats and recommends Airless for primers on large flat parts.
Airless
- Nozzle
- 0.23–0.28 mm (0.009–0.011" tip)dealer
- Pressure · fluid
- 124–145 bar (1800–2100 psi)dealer
- Consumption
- 120–150 g/m² per coatofficial
Technocolor's methods page recommends airless for primers on large flat parts (doors, tops, panels).
Curtain coater
- Consumption
- 120–150 g/m²datasheet
Not listed for LBA42 — only by analogy with LBA45.
Process and compatibility
- Substrate preparation
- Timber at 8–14 % MC, sanded to P150, dust off. Best to sand, stain and seal within 8 h. Over stain allow 30–60 min and test first; if in doubt put an isolating coat down.recommended
- Sanding
- P320 silicon carbide when fully dry; P400 under enamel. Machine sanding next day.recommended
- Don'ts
- don't change the LNB42 ratio (50 %, period)
- don't stack more than 3 coats of the whole system on LNB42 — film gets brittle
- don't use under white/pale non-yellowing finishes
- don't sand before 2 h — it'll gum the paper
- no ammonia cleaners on the finished surface
Storage
- Shelf life
- 18 months unopenedrecommended
- Storage temperature
- 0–35 °C, indoors, ventilated, out of sunrecommended
Safety: 2K polyurethane: isocyanates in LNB42 hardener, flammable solvents (LZC8643 is mostly MIBK). Spray in a booth with extraction, wear a carbon-filter respirator (A2P2 or better), nitrile gloves and goggles. Clean the gun immediately.
Mixed into
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).
- official page: properties, spray 120–150 g/m², LNB42 50 % w/w & v/v, LZC1026/LZC8643 10–30 % w/w & v/v
- official dealer search — no result; legacy product URL now 404
- IVM/Milesi TDS for sister clear PU basecoat LBA45 (with LNB42/LNB17/LNB20 + LZC1026): solids, density, pot life, drying, LNB42 & LZC1026 data
- Milesi US distributor procedure for LBA26 clear PU sealer: catalyst choice LNB42 vs LNB20, thinning by species, spray tip/pressure table for clear PU sealers, sanding/recoat
- LZC8643 = Milesi polyurethane slow thinner
- Technocolor application methods page
- Technocolor characteristics glossary (solids, thixotropy)
Not covered by the sources
- No LBA42-specific TDS found (Technocolor or Milesi); all numbers except ratios/coverage are derived from sister Milesi sealers LBA45/LBA26
- Official dealer t-colormarket.ru: product delisted (404) — no dealer solids/viscosity/pot life/drying
- Not in Technocolor 2025-2026 catalog transcripts nor any official finishing schedule
- Clear vs pigmented not stated officially (assumed clear from Milesi LBA code convention)
- Exact solids %, part-A viscosity, density, pot life, drying times for LBA42
- Packaging sizes
- Gloss of the primer film (n/a)
- LZC8643 SDS link no longer serves the PDF — MIBK content in safety text unverified (2026-10-05)
- Airmix fluid pressure: Milesi distributor 41–62 bar vs Technocolor methods page 'up to 20 bar' — no LBA42-specific setting