There are so many blogs out there telling you how to make laundry soap, and they are pretty much all the same. I've never seen anybody do it my way though, so I'm going to give you a step by step guide.
First, I recommend you go out and buy the three ingredients you need the next time you're at Walmart or the hardware store. Have them on hand because, if you're like me, you may find yourself on a Sunday night realizing its laundry day the next morning and you forgot to buy more laundry detergent. Its the perfect time to make your own and it will be ready for you in the morning.
Here's what you need: Borax, Washing Soda, and a 5-6 oz. bar of soap.
I've used Fels Naptha and I've used Ivory. You can use whatever you have on hand. Some people think the Fels Naptha is a little strong and irritates sensitive skin. We don't seem to have a problem with it in our family and I like the clean smell it has, so I use that sometimes, but I didn't have any problems or see any difference in the cleaning power when I used Ivory. The scent was much more muted (non-existant) with the Ivory as well. If you use Ivory, you may want to use 2 bars, because they are smaller. I'm not sure of the ounces, but when I made mine with Ivory, I used 2 bars and it came out really well.
I've recently started making my own bar soap as well, and when I make my next batch of laundry soap, I'll use my own bar soap, then I know my laundry will be chemical, dye and perfume free!
First thing you need to do is grate your soap. I use my box grater. It works great and its easy to clean. I just rinse it under warm water and pop it in the dishwasher.
Next, you fill a large saucepan with about 2-3 quarts of water and dump in your soap shavings. Cook the soap over medium heat until all the soap shavings are dissolved.
Now its time to add your borax and your washing soda. I use 1 cup of each. Pour them in and stir with the heat still on. You will need to cook it for a few more minutes to make sure everything is dissolved.
Once its all nicely combined, take your pan off the stove and move it to your counter or work space. This recipe makes about 3 gallons of laundry soap, so I use 3 empty 1 gallon vinegar bottles. Pour your soap evenly into your gallon jugs. I use my 1 cup measuring cup and dip out 1 cup at a time and pour it into each bottle. It turns out to be about 4 cups per bottle and it looks like this.
Now, take your jug to the sink and fill each one about halfway with hot water. Shake them well and leave them on your counter overnight, with the lids open.
In the morning, I close 2 jugs and put them away for later. The third one, I fill the rest of the way with boiling water, then I pour the water out into a big bucket. I cut the top off the bottle and dump the hardened soap mixture into the bucket and get out my stick blender. Blend until all the soap is broken up. I also added about 1/4 or 1/3 ounce of lavender essential oil for fragrance.
I like to store my soap in an old 1.5 gallon laundry jug with a spigot. My mom gave me her old Costco brand one that I reuse. It makes dispensing much easier. I pour my blended soap carefully into my recycled spigot-ed jug and I've got plenty of soap to last me a couple of months. When I run out, I've got 2 more concentrated ready to just add boiling water to, and mix.
A note about fabric softener: About the time I started making my own laundry soap, I also switched over to using white vinegar instead of fabric softener. I like that there are no chemicals in my laundry at all now and the vinegar does a fantastic job of softening my clothes, plus there is no vinegar smell left over. I just fill my fabric softener cup to the line in my machine.
Not only is this a very frugal way to do laundry, its also free of all chemicals and dyes. The Fels Naptha soap does have some perfume, so use Ivory or your own handmade soap to keep your laundry soap perfume free.