I'm trying to cook some dried corn that normally is meant for popcorn.
I've soaked it 36 hours using bottled water and then rinsed it multiple times with tap water.
After that I cooked it for about 1 hour, yet the corn is still hard? What do I do?
Popcorn does not soften.
There are five main types of corn: dent, sweet, flour, and popcorn. These types vary slightly in their composition but they share a similar basic structure:
Dent corn is used almost exclusively as animal feed. Incidentally- it is the only type that I ever saw for sale in Germany which might explain why all the Germans I met thought we were crazy for eating corn on the cob.
Sweet corn has a soft hull and much more sugar in the endosperm- It is eaten as whole kernels.
Flour corn has a couple delicious starches in the endosperm and a manageable hull. Manageable in the sense that it can be ground to release the starches.
Popcorn is unique in that the hull is freakishly thick and not porous. When the popcorn is heated the steam inside the kernel forces the hull to shatter- releasing the steamed starches which instantly solidify in the air.
The hull is made out of cellulose and is indigestible to humans and insoluble in water unless treated with inedible amounts of acid (or acetone). Boiling popcorn might partially rehydrate the interior starches but it won't soften or remove the hull.
Popcorn can be ground into a course corn meal. In this case the starches are mechanically liberated for our polenta or cornbread enjoyment.
I have never heard of boiling popcorn and was intrigued that @rumtscho said that she had seen it. The only single reference I was able to find online for boiling popcorn was to make parrot food. This website at least recommends cooking the corn in a slow cooker for 10 hours. This is in line with times for cooking whole wheat berries. You might give it a try.
There are different types of corn. Maybe you are using the corn for popcorn; that won't do it. You need the kind of dry corn for boiling: that won't take that long to cook.