Oh for goodness sake! It DOES NOT take a lot of scrubbing to get CHALK off- as a few of us have said,yes it probably takes more 'washings off' by rain or a hose,if that wall is 'sheltered' from rain,but if it is only chalk,it does come off in end...a good hosing down will help it fade quicker,but it will fade eventually.(unless sharpies or permanent markers are used,then will need a scrub.bleach should do it!) Anyway if its just kids rainbow pics why are some of you being so precious about it? Id have thought anything like that would cheer us up now not make you mean towards the kiddies! Even the 'new type of chalk' (which sounds made up cause ive got grandkids& never heard of it) will eventually fade off in all weathers,may take a bit longer..so why are being,yes,Killjoys!