Oh, the pain of not having an envelope to scribble on the back off when the need strikes. Fear no more! Here's a note-pad that's always available when you need to do a back-of-the-envelope calculation. It's also a great and handy way to re-use envelopes before sending them to the recycler.

Step 1: Gather Supplies

You'll need:

About 15 envelopes of the same size (This is a good amount for making one note-pad. Make sure when you're opening envelopes to use scissors to cut the short end - this makes them lie flatter when stacked, and keeps them the same size).
Binder clips
A couple pieces of scrap paper
A whisk
Heavy blocks (like textbooks) or a book-press
Paintbrush
Padding compound (see below for ingredients to make your own)

DIY Padding Compound:

1/2 tablespoon unflavoured gelatin
3 tablespoons boiling water
1 tablespoon white vinegar
1 teaspoon glycerin

My acknowledgments to Andrea Arch , from whom I got the recipe and instructions for making a note-pad.

Step 2: Clip It Up

Make a stack of about 15 envelopes. Any more envelopes and it gets a bit bulky on one end as the envelopes fan out a bit.

Make sure the backs of the envelopes are all facing up (this is the blanker side that you' want to write on). Keep the openings facing the same direction as well (remember, you'll probably want to use scissors to open the envelopes on one of the short ends, not the long end where the envelope flap is). The openings will be the bottom of the note-pad. If you put padding compound on the open ends, you run the risk of catching some air inside and causing bubbling.

Put a piece of scrap paper on the top and bottom of the stack, wrapping it around the edges is fine. You'll be removing the paper at the end. Put binder clips near the top to hold the stack together (this is the short-edge where the envelopes are still closed). Leave the edge that you'll be putting the padding compound on un-clipped.

Step 3: Padding Compound

Pour 1/4 ounce (1/2 tablespoon) of gelatin into 3 tablespoons of boiling water. Use a whisk to stir mixture until it has dissolved and no grains of gelatin are visible.

Add 1 tablespoon white vinegar and 1 teaspoon glycerin. Whisk for 1 minute until well mixed.

Pour mixture into a mason jar and allow to cool to room temperature before use. The mixture will be a jelly-like consistency when ready to use.

If mixture becomes too stiff to work with, throw it in the microwave for 5 second bursts until it goes back to a spreadable consistency.

(Slightly modified from Andrea Arch's instructions)

Step 4: Pad!

Place the pad between two heavy blocks or a press, leaving the edge to bind just exposed. Paint the padding compound generously onto the edge. Use extra binder clips to hold the envelopes together, if necessary. Be careful not to let the clips touch the padding compound. Let the padding compound dry and apply another coat. Repeat until the padding compound seems to cover the edge (about half a millimeter thick).