Backer Rod - anyone here use it? Difference between open and closed cell?

[udaman]

Hi all

Got plenty of caulking and filling coming up... I'd not heard of backer rod until recently, and having read up a bit on it it seems there's many others who are unaware of it. The big name stores don't seem to sell it either, which made me wonder how commonly it's used...

So, any fans of backer rod here for use in channels, chases, etc prior to caulking?

On a more technical note, there's a fair bit of online chat RE open vs closed cell. Apparently, open cell is more pliable/flexible and better for squeezing into gaps but not good if it gets wet. Also, they say closed sell off gases when cut or torn which can cause problems and even cause the caulk to bubble. But that's mainly from US sites/forums. Here in the UK, there's not much talk of it and the shops that do sell it seem to just sell "standard" stuff (which is closed cell). Does anyone know anything about this open/closed cell business?

Cheers

[udaman]

Not many users of back rod here?

[big-all]

sorry never used it as you say i had to look it up