Yay! I am finishing up one more (green). The red, blue and yellow are heavy (140lb) watercolor paper which is what I use for journaling (it’ll take pretty much anything, including tons of water and beeswax) and the interoffice (and upcoming green) are 70lb which is good for most dry media but will take limited amounts of water. I’m trying to decide if going all the way to 140 is worth it — based on this, my personal preference is for the really heavy stuff (although 70 is fine).
I love the used-ness of the interoffice envelope, but I didn’t think it would be a good idea to have peoples’ full names on there so I had to scratch them out. Not ideal but it looks OK I guess. Most importantly, the envelope is still open-able and the book can be closed by looping that red string around the little … thingie… (technical term); you know, like the original envelope. It’s nerdy but I love it!
I need to figure out a new configuration to take photos because they are coming out too dark or yellow. I’ve adjusted this one in paintshop but it looks blah to me. Apparently finding a free box is impossible, so I may have to just go out and buy a box to make a little light box. Or maybe I could just buy one of those little table-top light boxes. But cardboard boxes are way cheaper, which is usually how I make my decisions. 
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Not too nerdy though. The interoffice envelope book is just nerdy enough to be really awesome.