Can you see any factory dates on the bags? You can also buy one bag from the batch, make up some putty, apply it to something and make sure it hardens up properly over a week or whatever.Right! I'm about to actually have a go at this. I've never actually made putty with hydrated lime (only slaking quicklime) but wondered about it for the ease of getting the hydrated. Wondering how I best tell if the stuff at the local builders' merchants is viable? Think they sell the Blue Circle stuff. Anyone have any hot tips here? The nearest dedicated lime supplier is about an hour away (for quicklime or hydrated). Cheers!