As a kid I remember my grandfathers tales of WWI and how he used to have to eat hard tack by soaking it in rainwater in his helmet. I always wanted to try hard tack and finally made a batch of it last night.
All of the recipes I found were all variations on the same theme and all of them gave different instructions for heat and baking time. What it comes down to is you're making a hard, thick cracker and it doesn't matter much how you go about it. The method I used was as follows.
5 cups flour (unbleached if available)
1 tbsp salt (more or less, it's optional)
1 tbsp baking powder (also optional)
(some recipes also called for 1 tbsp of sugar, I didn't add any)
1 and ½ cups water
Preheat oven to 425 degrees.
Mix dry ingredients first. Add 1 cup of water and work into stiff dough. Add additional water by ¼ cup at a time until the dough is pliable but doesn't stick to your fingers. Don't over do the water; keep working the dry looking dough if possible. You should only need 1.5 cups of water max.
Roll dough out to a ½ inch thick slab on a greased cookie sheet. Score the dough with a knife into 3x3 inch squares. Poke 9 holes all the way through each square in a 3x3 pattern with a large nail.
Place on center rack of preheated oven for 20 minutes. Keep checking until the center of the dough is golden brown and the edges are slightly darker. To make hard tack really hard once it is cooked turn the oven off and let it sit in the hot oven as it cools.
As long as you don't burn it you really can't mess it up. The center may me a little flexible at first but that slight moisture will go away as it dries totally. The stuff is hard as a rock when it's done drying.
It is easy to see why this simple bread; was issued to soldiers. It is low cost, easily made, and indestructible and as long as you keep it dry it won't easily spoil. Traditionally it was soaked in coffee or soup. Some wrapped it in a moist cloth for a day or poured boiling water over it and flavored it with syrup. Trying to eat it raw can damage teeth so be careful.
Mac