Renner M404 Hardener for 641 Water Primer 2.5Kg
The hardener is what turns a good water-based primer into a coating that survives a kitchen. Renner YC-M404 is the catalyst for the YL-M641 water-based primer, converting it from a 1K product into a two-pack system.
What catalysing changes
- Durability. The cured film is significantly harder and more resistant to handling, cleaning and knocks. It shows first at door edges and around handles — the places a finish gets tested daily.
- Grain raise on MDF. Catalysing reduces the fibre lift that otherwise leaves machined edges and profiles rough after the first coat, so you sand less and lose less of the primer you applied.
- Suitability for kitchens and bathrooms, where the finish faces moisture and constant contact rather than sitting quietly on a wall.
Why the tin says "solvent based"
This one catches people out, so it's worth being clear about.
M404 is a polyisocyanate hardener, and polyisocyanates are carried in a co-solvent to hold them at a workable viscosity. The label reflects what is in the tin, as it has to.
It does not mean you are working in a solvent system. M404 is for water-based products only. Added to YL-M641 at the correct ratio, the mixed and applied coating is water-based, and equipment cleans down with water.
Mixing
Add at 2–10% by weight to YL-M641, depending on how much performance the job needs. Mix thoroughly and work inside the pot life — once catalysed, the clock runs whether you are spraying or not. Only catalyse what you will actually use; what is left in the pot at the end of the session is waste.
Handling
Contains isocyanates, which are respiratory sensitisers. Work to the current safety data sheet and your own risk assessment: isocyanate-containing two-pack products carry specific respiratory protection requirements for spray application, and a cartridge mask is not always sufficient.
Match the hardener to the primer
M404 pairs with M641. If you are running the M643 primer instead, that takes M402. The two systems are not interchangeable, and the wrong catalyst gives a film that never reaches the properties you paid for.
2.5kg. Clean spray equipment immediately after use, before anything begins to cure inside it.
Ireland & Northern Ireland — 1–3 working days. Charged by total order weight, VAT included:
- Up to 30 kg — €6.99, or free on orders over €85
- 30–60 kg — €13.99
- 60–100 kg — €27.99
- Over 100 kg — pallet delivery €49.99
Great Britain — 2–4 working days. €13.95 up to 30 kg, then €27.90, €55.90 and €99.90 by the same weight steps. There is no free delivery to Great Britain.
Rest of Europe — non-liquid items only, from €11.75, priced by destination and weight at checkout. Paint and other liquids ship to Ireland, Northern Ireland and Great Britain only.
Dispatch and collection — order before 12pm Monday to Friday and it ships the same day. Click & collect at Ballymount, Dublin 12 is free and often ready within the hour.
Returns — 14 days to change your mind and 14 more to send it back. Tinted paint is non-returnable once mixed.
