The magic numbers are 3:3:5.
Three parts (by weight remember!) of borax to three parts of bar soap to 5 parts of wash soda.
That's it. Three ingredients.
Step 1: Weigh It Out
In this Instructable I'm using the ratio to make around 550 grams of detergent. It's not critical to get precise measurements for this. The soap I used only measured in at 125 grams. Just get it in the ball park and you're good. Of course if you're scaling the recipe up you'll want to try to stay fairly close as you scale up or the ratio will get all out of whack and you'll get less than stellar soap.
I used 150g of borax, 150g of soap, and 250g of wash soda. Mix it all together.
Just as an example:
A ratio of 3:3:5
Add some zeros.
300g : 300g : 500g
Then divide by 2.
150g : 150g : 250g
Multiply and divide as needed.
Step 2: Going The Extra Mile
Toss the soap into a food processor and take it for spin until it's a lovely uniform powder. This will insure good and fast dispersion of the chemicals in your wash water.
Step 3: Done, Use, Cost Breakdown, And Thoughts
I use 1 tablespoon per load. That's it. If you've got heavily soiled things, bump it up to 2 tablespoons. If you've got a huge washing machine 1 tablespoon will probably work, but as all machines are different experiment with the amount the first few loads. The goal is to use as little as possible and still be effective.
We've all been duped for years with the scented detergents on the market. Your clothes shouldn't smell like the soap you wash them in. They shouldn't smell like anything after coming out of the washing machine. Commercial detergents are packed with perfumes to get that effect. Who needs that crap? The soap you choose for this is a personal choice. I pick soaps that are pleasant smelling to me because that adds a perk to loading the laundry. I get to smell it. It's cheap aroma therapy. But I don't want my clothes to smell like it. If you're clothes smell like your soap you're using too much or your machine isn't doing a good job of rinsing it all away.
A lot of these recipes will call for you to use Zote soap. I don't recommend that. It clogged my front loading washer's soap tray after a while. Zote is a good and cheap stain pretreater (just rub it into it), but I'd avoid it for this purpose. Fels Naptha is another that people use. I have a bar, but have yet to try it, but it's not tallow based like Zote so I don't think it'd be as likely to clog your machine or pipes. It's fragrance is just so so. So I'll stick with trying various bar soaps that make me feel good to smell them.
Borax ~ $4 (2155g) --- price per gram $0.0018
Soda ~ $3.5 (1560g) --- price per gram $0.0022
Soap ~ depends on what you're looking for, for this Instructable $1.50
So (150g borax x 0.0018) + (250g soda x 0.0022) + $1.50 = $2.32 for about 550grams of laundry detergent
One tablespoon is between 13g and 15g. So each load costs (2.32/550) x 15 = $0.06 per load
Number of loads you can get out of the 150g:150g:250g batch is (550/15) = 36.6 loads per batch this size
I've bought the soap I used on sale before for $0.99 so this batch of soap could cost (2.32 - 0.50) $1.82.
Forgive my math skills. If I've made an error please correct me so I can change it.
It's cheaper, if enough people made their own it would cut down on fuel used shipping liquid detergents, plastics used to contain them, cardboard in the case of powder, and who knows what kind of crap makes up an average store bought laundry detergent.