I got a treadle yesterday, and I was sewing along on it, and then the stitchs bubbled up on the bobbin side, and sort of of the top. The other half of what I sewed was just fine, so what can I do to adjust the tension? I was pumping it pretty hard, did it vibrate and change or something? Did I thread it wrong? It is I believe but am not sure, a singer 99, 99-13?
Thanks
Emily

Did you take the thread out of both top and bobbin and re-thread? I doubt that the tension adjustment would have changed on its own while you were sewing. It's more likely that a tiny piece of lint or thread is caught in the bobbin area or between the tension discs. Threading the machine wrong can cause this problem too, but I gathered you had not re-threaded between the time it sewed fine and the problem?

Did you oil the machine? Those old machines have a lot of oil points, both above and below.

The only other thing I can think of is that possibly you were going so fast the treadle delivered a reverse 'blip'. I'm sure that's the scientific term for it. :? I know when I used a treadle years ago, I could make the machine sew backwards as well as forwards -- and not always with intent. It took me awhile to get the rhythm right so I didn't inadvertently reverse the sewing.

Thank you for your reply! After I oiled the head, and rethreaded it, I found out I was making the tension looser, not tighter, so I adjusted that, and it is working fine! I try to keep a steady pace as well, I found it doesn't go as well when it is fast.