Some time ago, I started buying pipe tobacco by the pound. I needed a way to keep it at the proper 12% to 14% humidity and bought those 25 cent sized disks for about $1.50 each (2012 prices). But these wear out and after 3 or 4 uses have to be replaced. I though I needed a way to humidify without the cost and with the ability to renew the humidity inexpensively. I had no idea of where to start. But, as with many inventions, I got lucky. I was reading at Pipepedia about scans (.jpg) of a Wally Frank catalog. Fascinated I read each page and what-to-my-wonder, there were those disks. And the description said they contained "Aztec Clay". I thought I would never figure out what that was, but to my astonishment, a quick netsearch showed that Aztec Clay is the same as Bentonite Clay. A year went by while I tried to figure out how to find a container with holes on top to allow the humidity from the clay to be effective. And, as always, the solution was found in the most unlikely of places. I was in a woman's beauty supply store and saw round, plastic discs with holes on one side (In 2016 I learned that they are called eyeshadow sample jars.) They screw together and form a tight unit. So, I purchased two of them. I purchased some Bentonite from eBay for about $1.00 (US) an ounce. My seller had free shipping. I took the clay and the discs and in a small bowl mixed about 2 heaping teaspoons into the bowl. Slowly I added water to make a thick clay and then a little more water to make the clay pliable. Using a spoon I pushed the clay into the bottom of the disc. Once it was full, I screwed the top on, wiped off the excess clay and voila! it's ready to go and keep my tobacco moist. I haven't needed to re-moisten clay just yet, after about a week. When it does need more water, I'm going to add only a 1/4 teaspoon to the already formed clay disc, let it sit overnight on a table to allow time for absorption and put it back into the tobacco, the next day.