Part 1: Some basic principles I’ve followed from the get-go (or developed on the way)
1) Materials need to be inexpensive. That means I’ve used a lot of up-cycled fabric- old T-shirts, sweatshirts, and fleece items. Plus some cheap fabric- almost always $1 a yard or so. I’ve never tried much with PUL- in large part because it’s expensive, and when I started, there wasn’t any available locally. Now I have bought a little to experiment with, but none of it’s gone to a diaper yet, and at $9 a yard at the local Jo-anns, it probably never will.
2) It has to perform better than a white pre-fold. It especially has to stop liquid from just dripping right on through, and needs to keep any moisture wick-age from happening for at least 15 minutes (okay, that’s just a ball park figure, but you see my point? I don’t want to have to change an outfit every time I change a diaper. That means that in all of my diapers, regardless of the pattern/idea I see that I’m trying to follow, I add in a water resistant layer. Usually a cheap, $1 a yard fabric like nylon/ripstop nylon. Since the odd fabrics often don’t have listed exactly what they are, it’s a judgement call on if it will work well. Fortunately, it doesn’t usually take a lot of it, so a few yards of “good” stuff go a long way.
3) I’m finding it increasingly desirable to have a diaper that doesn’t need a separate cover. One less layer, one less hassle. They don’t just sit there perfectly still for you, so I want as quick a change as possible. That means I’ve changed from T-shirt or flannel outer layers to fleece (usually). The fleece doesn’t wick the moisture around the legs or onto the clothing. Plus it’s soft to the touch and you can usually find a decent pattern/color or add a little embellishment easily. especially since it doesn’t fray or unravel. Also handy in some of my designs that have only the fleece layer in some parts of the diaper, and I like the extra form fitting you get from a little stretch in the fabric. Thickness has an impact on where I use it, though. Some just aren’t as good for outer layers or covers.