Is it hard to do? Does it work? What is washing soda? Where can I find the ingredients? How much can I save?
I'll attempt to answer those questions and give you a better idea of how to go about it and what to expect. You can post your further discoveries or questions to the Frugal Living Forum and expect a good answer.
Washing soda should be in the laundry section of your grocery store. It comes in a yellow box, made by Arm & Hammer, but it's NOT baking soda. If you're interested, washing soda is Sodium Carbonate (Na2CO3), baking soda is Sodium Bicarbonate (NaHCO3), and borax is Sodium Tetraborate Decahydrate (Na2B4O7*10H2O), all different chemical compounds.
If you can't find it locally, call this number: 1-800-524-1328. It's the Arm & Hammer number and they should be able to tell you where the closest place is that you can find it. There are places on the internet where you can order it, but shipping costs will eat up a portion of your savings, so that would be a last resort.
Some recipes call for borax, which comes in green box. The most popular brand is called 20 Mule Team Borax. This has been around as a cleaning aid for many years and is also known as an inorganic pesticide and herbicide. Borax is a naturally occuring substance used for cleaning and whitens and lightens clothing.
The "20 Mule Team" comes from the fact that borax was mined in Death Valley in the 1800's and hauled out of the desert by 18 mules and 2 horses at a time. Two wagons loaded with borax and a wagon carrying 500 gallons of water traveled over 165 miles of desert in 10 days. That's probably more than you wanted to know, but it was quite an enterprise at the time.
You can use any bar soap you like to make it, but what is probably the original recipe used Fels Naptha, a old stand by - the yellow soap your grandmother grated into her wringer washing machine. They still make it and it's still good:
Fels Naptha The one and only, yes!
How to do it
Some people shave the bar of soap into a pan of hot water and stir until it's dissolved, but there is a lazy way to do it. Break or cut up the bar soap and put it in a pan of warm water one night. Let it set over night, then stir until it's dissolved. Heat it if it's stubborn, but it won't take nearly as much time or stirring this way.
For those of you who are outside the US, put about 10 - 12 litres of hot water in a bucket and, after adding the dissolved soap bar, add 250 ml washing soda, and half that of borax (if you use it).
After the soap is dissolved, put about three gallons of hot water into a large container. Add the soap, stir in well, then add a cup of washing soda, stirring until dissolved. If you want to use borax, now is the time to add a half cup or so.
Set the whole thing aside until it cools, when you'll discover a gelatinous mass, vaguely of the same color as the bar soap you used. Depending on the strength of your soap and how much water you used, you'll need 1/2 to 2 cups of this laundry soap for each laundry load.
How much it will cost
It's easy to figure how much you'll save this way. Add up the cost of the bar of soap, divide the cost of washing soda by six (that's about how many cups are in a regular size box), add that, then figure the cost of borax the same way. (There are about eight cups in a regular size box of borax.) Now divide that figure by 48 which is how many cups are in three gallons.
One bar of Fels Naptha soap - .79
1/6 of $1.99 box of washing soda - .33
1/16 of $2.49 box of borax - .16
(Note: Prices were from a few years ago and have probably changed, but so have "regular" laundry detergent prices. You can get a good idea of prices by looking for the product on the internet.)
Divided by 48 = .0266 or less than 3 pennies a cup.
Does it save you money? How many cups are in the box of detergent that you normally use? Yes, you'll have to measure them yourself. Just pour it, cup by cup, into a measuring cup and then into a large container, counting the cups. When you know how many, divide what you paid for it by that much. Ouch, huh?
The only thing left to figure is that if you use half the recommended amount, halve the cost per cup and that's how much a load of laundry costs you with your present detergent.
I will bet that it costs more than 3 cents.