In short, a lot of research and advice from others. It was important to me that the soap I chose to use wouldn't leave a residue. From my experience thus far, the Dr. Bronners and Fels Naptha work great. I've also heard Ivory and Zote work well too. Some people prefer their clothes to have a fragrance from their soap, so my best advice is to experiment and over time you will find what you like best. You can also experiment adding in a few drops of essential oils to the mix.
3 Gallons Water
1 Cup Borax (5 oz dry weight)
1 Cup Super Washing Soda (10 oz dry weight)
1 Bar Fels Naptha Soap (5 1/2 oz dry weight) Walmart Prices on Ingredients:
Fels Naptha Soap- $0.97
Box of Borax- $2.98
Box of Washing Soda- $2.68
Coupons I used:
$1.00 off any 2 Arm & Hammer Laundry Items from 4/10/11 Smart Source Newspaper Insert.
$0.35 off any Fels Naptha Bar Soaps (Got this one by emailing the company for current coupons)
To make a long story short, here is my cost breakdown for each batch:
Fels Naptha Soap- $0.62
Box of Borax- $0.20
Box of Washing Soda- $0.40
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That's a total of only $1.22!