posted 07-24-2012 10:51 PM
I have always tried to use 100% rag content (cotton fibre) envelopes, but sometimes had to settle for 25% content.
When making my own envelopes (converting the paper to envelope shape), I try to use a 100% paper there too. Office supply stores have the sheets... but envelopes are tough to find.
Artmaster (Louisville, Ky) used to sell the blank stock they used, but they've closed up and gone away. My last box of 300 came from them and I use them sparingly. Seems like the 10-cent each range was a price I usually paid from them.
Southworth envelopes were the locally available brand in the small office supply stores locally, but those stores are as gone as Artmaster. But I think Southworth is still around.
My cachetmaker friend, Helen Fowler, in Niles uses a die-cut envelope paper. She was having it produced specifically for her use. She likely would provide any details of what she is using if you contact her. She trades on eBay as 4flagstampsandcovers or you can search her under Compuchets and you will find her website and contact information. She is totally into computer-generated first day envelopes.
After typing and reading this, I am not sure I really answered any of your questions. Sorry.