Excuse me Laundress but I knew that soap was made thanks to sodium hydroxide very basic substance (Castic soda), not sodium carbonate (washing soda), at least this is what I make home made soap bars with......
Me and my sister have tried to make home made soap with it and came out very good
.....
If you want I can give you guys our recipe, is very simple to make, just requires some caution, you have to be careful nandling caustic soda as it is highly corrosive, we tried making Marseille soap with olive oil, also we got soap bars with corn oil and peanut oil, you just have to know the coefficient of saponification of every oil to calculate every percentage of sodium hydroxide needed from oil to oil actually you can do it with every kind of fat, we also made it with corn oil and peanut oil....
And we added essential oils for perfume, i made great laundry bars lemon and lavender scented.
Actually I think laundress "confuse" washing soda only with the old laundry lye that once was obtained in the old days by filtering wood ash boiled solution, that one contained some percentages of sodium hydroxide also along with sodium carbonate...lye is the modern word that refers to caustic soda very corrosive substance that was obtained by wood ashes as well, at least this is what wikipedia tells me.
Now I'd need to make some distinctions:
Lye as said means also a strong solution of sodium hydroxide actually used to make soap, obtained in the past as well by wood ashes and by boiling it for more time I guess, while laundry lye was the one used on it's own for laundry and dishes obtained by boiling ashes solution for less time I guess actually making a "soda ash" rather than a lye whre hydroxide was the major component rather than sodium carbonate (soda ash is the old name for washing soda).
I think the website makes some confusion and calls lye both the things....
So all 2 kinds of "lye", caustic and "less caustic" were obtained of course by boiling and filtering wood ashes,laundry lye or soda ash was used as cleaner alone or with soap but over sodium carbobnate (washing soda) it also contained little percentage of sodium hydroxide due to the fact of the antique boiling extraction method that actually could produce corrosive potassium or sodium hydroxide if boiling was prolonged, actually they tasted the soda ash mixture by dropping a drop on the tongue and as it was itching a bit it means it was ready, anyway is the old soda ash or "lye" the one that was harsh since it would contain always some hydroxides in it, it couldn't be sodium carbonate only..... and this explains why the irritated and red hands Laundress mention.
I also used to see here in Italy a packed form of laundry lye (Lisciva) called: Lisciva la sulfonella", actually the main ingredient is sodium carbonate and no traces of caustic soda in it.
So Lye intended as caustic soda is the corrosive substance with whcih you make soap, while laundry/cleaning lye or soda ash is the one that most fits and is similar to the washing soda even if as said contained traces of caustic soda, washing soda intended as (sodium carbonate) alone indeed is not corrosive and also saponification process cannot be made from it.....
[this post was last edited: 8/23/2012-11:53]