What is hardener?
Hardener is an optional additive that can be used with the Renner Waterbased Primer.
What is it for?
It hardens the paint. Therefore you may consider adding crosslinker to your topcoat if you were spraying bare MDF or previously treated wood as it can help with fibre raise and tannings.
If you do decide to add a hardener to your primer please check that you're mask provides you with the adequate amount of protection.
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