I remember seeing this on another forum some time ago, a fella varnished a piece of timber and later applied in sections on the timber, zinsser bin, zinsser 123, macphersons undercoat, acrylic primer, crown solo gloss and crown solo satinwood, I'm almost sure that these were the paints used from memory. Anyway he returned to the piece of timber weeks later so the paints had fully cured and he then took a stripping knife and ran it across the timber applying even pressure. The zinsser bin and 123 came off easily as did the acrylic, the oil undercoat held up fairly well, but the crown solo gloss and satinwood didn't budge. It's worth searching the net for this as it is an eye opener for some people, I wish I could remember which site it was on. After a while he went back to the same piece of timber and did the stripping test again and the acrylic primer didn't come off !! which tells me that the acrylic must need a hell of a long time to fully cure.