Witcher 1 sword critical effects

I am testing how critical effects written on swords work and for example Aerondight has 50% chance of incineration, but no matter how many blows I do it will never proc incineration effect on enemies.

Does that mean that if I just have Aerondight in my inventory I have a 50% additional chance of triggering incineration, but by means of skills that actually produce incineration, for example Igni sign. So the sword itself does not in fact trigger this effect when hitting enemies, it just raises the chance of triggering it for the skills that can apply it?