Basically it's the same for laundry as for dishes, only leave out the salt/citric acid and add in a grated bar of soap.
Here's what it takes:
- 300 g washing soda
- 150 g borax
- 1 finely grated bar of soap
Thin and stringy like "fancy" shredded cheese is fine, doesn't have to be all powdery. We use Zum soap, usually frankincense and myrrh. The grating process acts as a whole house air freshener. And we get it from the 91st and Metcalf Whole Foods because we can get it without any packaging there by cutting off whatever size bar we want. We end up getting about the size they normally sell as a bar anyway, which is about 85 g.
I currently do all my laundry in cold water, both because it saves on heating the water and because it allows me to be indiscriminate when sorting clothes. I've gotten into the habit of separating into three categories, generally only one load of each: shirts, pants (dress/jeans/skirts), and everything else.
All you need is one tablespoon per load*, dropped in the washer before you begin filling. And like any powdered detergent, wait until it's filled up some before you start tossing in your clothes.
One important note. The place I learned this recipe (sorry for no ref) seemed to indicate that this detergent is perfectly safe for use in HE washing machines. The theory is that HE washers have problems if your soap gets too sudsy. And this, I believe, doesn't gets sudsy at all. That said, don't come whining to me if you do it in an HE washer and you break it. I guess all I'm saying is that if I had a washer labelled as HE, I'd totally try it. It'd be worth a shot; we're at least halfway considering whether we could try doing laundry without a machine. No promises there though.
*I realize now that here and with the dishwasher detergent, I used tablespoons when I had been very careful about using metric measures in my weights. So if you care, it's just shy of 15 mL.