If you mean it's hardened and you want it crystallised again, the grinder is the way to go. If you want to keep it from getting hard in the jar or bag, put in a cream cracker/saltine or piece of bread to absorb the moisture. You do have to check this every so often because once the cracker/bread has done it's job to the max, the sugar will start to get hard again. To really soften sugar, put it in a nonstick pan over water (in a double-boiler--don't put water in the sugar). The heat will melt the sugar and it will just be syrup then.