Hi,
I am attempting to make a drybag packliner with the 40d fabric, both because I need one and because I want to get the hang of this before trying to make the raft. (and I am waiting on the release of the new UL kit!)
Anyway I got my iron and checked the temp with a IR thermometer I have. I adjusted the thermostat so that the tip of the iron was reading 200 and the center was reading as high as 225. (one post on the form said 200-225 was a good setting)
I decided for construction to bond the two tpu sides together in a 5/8 inch seam (this part went well), and then to cut a strip of fabric to bond to the outside of that seam, creating a stronger and more likely watertight seam.

I got a lot of bubbling, and air pockets. I am not sure why this happened, it seemed to happen even if I was careful to start at the center and move the iron to the outside. Here are some pics. Can you tell me what went wrong?