Oh lord, I said I wouldn't, but..
Look, Kenmoreguy89, I dont want to dive headfirst into this mess you are doing your best to create, but it looks like I'm gonna have to at least dabble my toes in the water. Launderess was not confusing lye and washing soda. Her statement was correct. Sodium Carbonate does help to convert oils and grease into a soap like substance. No, it is not often used now, but if you dissolve it in boiling water, pour in melted grease, and cook it, you get a sort of soap jelly one can use for cleaning. Boil it longer and add a few other things, you get soap bars.
How do I know this? My great grandmother used to make it, as well as making lye soap. Lye soap was for laundry and household cleaning, Sal soda soap was for bathing and cleaning people. And she did not use wood ash lye in place of Sal Soda, such as you mentioned, she used store bought Sal Soda, which has been available in this country for a few hundred years now, and in europe as well.
The theory you give as to how this, "laundry lye" was extracted, and boiled to turn it into regular lye, is incorrect as well. Perhaps in major manufacturing, or perhaps in your home country, but not here. One did not use weak or once filtered lye for anything. Lye was made by filtering the solution through the ashes over and over, adding fresh ashes as needed, until it was strong enough. No, it was not as pure as store bought, containing traces of Sal soda, but when things are homemade traces of impurities and other such things must be tolerated. If a waker solution was needed, the now strong lye was watered down.
Sal soda was not made at home at all, it was purchased by the pound.
And no one with any respect for their body would have tested the lye on their tongue. Lye was not strong enough to make soap until it was also strong enough to burn and become caustic to human flesh. If one tested the lye on their tongue for strength, it would not itch, it would burn their tonge and leave a wound.
Lye was considered strong enough based on 2 main tests. It should be able to make a fresh chicken egg float, and if one drops a chicken feather into the lye, it should dissolve. That is not something one wishes to drop on their tongue.
All this palaver of making, testing, etc, is why women in this country readily took to store bought lye when it became available. However, they did not forget how to make it themselves, as store bought was not always affordable, or handy when one needed to make soap, depending on ones finances and distance from the nearest town.
There was no need to say Launderess was confused, when she was correct and had references to back it up, as you would have known if you had taken the time to look, or ask others if you thought she might be wrong, rather than attempting to state it outright. As well, there was no need for that childish display of online yelling and temper tantrumming when she said she was offended. This is a civil forum, and I would like to think we can all conduct ourselves in a civil manner.
And if you still dont beleive washing soda/sal soda/sodium carbonate will make soap, here is a recipe similar to my great grandmothers, for english bar soap, made not with lye, but with sal soda, which is washing soda, which is sodium carbonate. Not sodium hydroxide, which is lye.