Kilner jars with clip on lids are excellent for jams and chutneys, and are very resuable. I find the best way to clean them is to take them apart, removing the metal clip, and wash the jar, lid and rubber seal in the dishwasher. To remove the clip, the normal way is to pinch the two arms on the lid together. The lid can then be removed. Then remove the clip holding the bottom part of the clip on. Be careful here, because it can ping across the room. Remove the rest of the clip. Don't wash the clip in the dishwasher and they are normally made from a mild steel that can rust. Wash in a basin of hot, soapy water, rinse, and dry immediately. New rubber sealing rings are readily, and cheaply available.