I have a 3/4 full can of shellac that's been on the shelf for over a year. Lid is tight, no problem with the contents, but the top sides of the can started to collapse. I used a little the other day and put everything back and the bottom of the can developed a hole and leaked onto the shelf until it built up enough around itself to clog the hole. I drained the material from the can and put it in a plastic container with a lid. Can I store it in this or must it be glass or metal? Is this normal for the can to deform over time based on this contents? Thanks Brian