Quote Originally Posted by Joshua
I forget the procedure, but you can bake your baking soda in the oven to turn it into washing soda. Then I think you mix 1 part WS in with 6 parts BS for a nice balanced mixture. I may be off on the ratio...
You can buy Sodium carbonate at HEB. Its Arm & Hammer Super Washing Soda and can be found on the same aisle with the clothes washing soap.

Whatever you use, it needs to be pre-diluted before adding it and added slowly or it will just precipitate out calcium as Richard said. We're going to do a workshop on DIY chemicals in one of the meetings coming up.