I'm in the process of building an earth bag dome, and I'm trying to figure out the right mixture of water to dirt. I've seen people say that it doesn't take much water, but what does that really mean? I've done a few bags with about 1-gallon of water in a wheelbarrow mostly full of dirt. And I did a few bags with closer to 2-gallons of water mixed with the same amount of dirt. The wetter bags were leaking some water out after a couple of hours, but when they dried, they felt as hard as rock. The less-wet bags did not leak any water out, but the next day they only felt solid from the top. If I poked the sides, they felt... slightly crumbly? soft? I'm not really sure how to describe it. Can anyone describe what the bags should feel like after they've been tamped and left for a day? Also, how long can I wait between filling the bag and tamping? It's hot, sunny, and dry here, and I'm worried the bags might dry out before I can finish an entire course and go back and tamp them.
Any advice on how to know if the bags are done properly would be helpful!
I tried to make my mixture slightly sloppy. I aimed for some seepage of water when I was tamping and they seemed pretty firm when tamping was complete, and they still are 2 years later. I was not building a dome though. It also depends on the nature of your fill material. Owen Geiger helped me to relax when it came to choosing my fill material by suggesting that if the structure I was building wasn't a dome or a 2 storey home, that I could probably use nearly anything that wasn't organic to fill the bags. I hope you'll be careful to keep the bags' sun exposure limited. It's scary how quickly they deteriorate in summer sun.
When I built my earthbag foundation I found that wet bags were superior to bags that had drier mixes. I think I read in an earthbag book once--don't remember which one--that the wet bags when tamped bonded the sand and clay better. This is also the experience when doing cob too. I did remember this website https://www.northernarchitecture.us/earthbag-building/the-dirt.html that talks about "weeper bags", and that they found them better to dry harder than traditional drier mixes as well. When you tamp a wet bag, they seem to not compact quite as well due to the liquid content, so you end up with a less flat bag. You want to tamp the bags the same day they are filled. I would lay down twenty bags, then tamp to use different muscles.
Depending on your weather, the bag should feel pretty hard after a few days of drying in warm weather. Obviously the cooler and higher humid the climate, the slower they will dry. All I can say is that after I finished my earthbag stemwall I accidentally backed into it with the hitch on my truck and it only ripped the bag and didn't do anything to the wall. I was using roadbase mixes from a local quarry.