You will need:
1 and 1/2 cups of baking soda
1 and 1/2 cups of washing soda
7 oz bar of soap
~ It works best with a food processor or blender. ~
1) Grate the soap with a cheese grater first to get it into smaller pieces.
2) Mix together the sodas and the soap in a large bowl.
3) Put the mixture into a blender or food processor and process until it looks like a finer powder mixture. (Or mix it by hand until it is of the same consistency.)
4) Pour into a sealable, airtight container (I use a half gallon mason jar with lid, as you can see from the picture) and store until needed.
~ 1/8 cup will do one regular large load of laundry, although I use two scoops, or 1/4 cup, for diapers and heavy-soiled clothing. Recipe makes about a quart of dry detergent, so it will last about 32 regular loads. I am pretty sure that it can be used in HE washers because of the fact that it does not sud up a lot like normal, non-HE detergents.