baking powder questions

I have been baking muffins recently. I opened a can of baking
powder, which was not past its expiration date or even close to
it. I realized last night that it must, nonetheless, be old,
because the muffins just are not rising much. Sooo, I am wondering:

  1. Does BP age in an unopened can? I note that the cans are not
    all metal now, so I imagine the cardboard would not offer the same
    level of protection.
  1. Do all double-acting BPs have the same leavening power? The
    one I have open is Rumford, but I have always used Calumet in the
    past. For some odd reason, Calumet is almost impossible to find
    here now.


KW, once again, thanks for your knowledge. It’s also a good reminder to all of us. Over mixing, as KW mentioned can be a reason muffins aren’t light, airy, & rise as expected. Yes, old ingredients is another.

I also agree, I can’t find Calumet BP anywhere here & the last BP I bought was NOT in a tin. Now that the idea has been passed along, I certainly can enclose in a container on my own.

So many hints here, love this site! Thanks everyone.