craftgrrl | sewing machines and candles and milk jars o my

Hi - I have two questions that are entirely unrelated.

1. My (mother's) sewing machine started giving me wildly uneven stitches, and sometimes it looks like it's not even picking up the bobbin thread. it's not consistently performing poorly, though - it will go for a minute or two with nice stitches and then fail again. ALSO, the thread keeps breaking. I googled both of these issues, and everything I found basically said, "check everything ever on your machine." which I will, but I was wondering if anyone had previously experienced that exact combination of failure before, so I could know where to start. it's a pretty basic New Home machine, if that matters. I think she got it off QVC maybe ten years ago.

2. we have these sweet quart glass milk bottles from the milk that we buy, and my mother (again) wants to use them as candle holders. the bottles are much larger than most candles though. she propped one in there with nothing today, which looked cool until the flame touched the glass and the bottle exploded. has anyone ever done any sort of craft like this? can you suggest things that we could put in the bottom to hold the candles?

thanks in advance!