Just to reinforce what
@CreativeWeirdo and
@DeeAnna wrote above...
By
legal definition, "Castile" soap contains no animal fats. So Kirk's Coconut Castile and Dr Bronner's Mild Castile Liquid Soap fit the description although neither is 100% olive oil.
Traditionally,
purists within the soapmaking community consider:
Castile =
100% olive oil
Bastile =
70% or more olive oil plus other fatty acids provided by fats like coconut and castor to provide the hardness and lather that olive oil alone lacks.
ZNSC owes its hardness. lather, longevity and "no slime" characteristic (common to 100% OO castiles) to the use of 0% SF and, as
@DeeAnna pointed out, to the use of faux sea salt used to create the soap.
@CreativeWeirdo is correct.
"Bastille soap" isn't an official term.
"Bastile" is "Bastardised Castile". It refers to soaps high in olive oil and exists only on soapmaking forums like SMF. There is no such thing beyond that connotation.
So I am asking if 50% OO would be high enough to retain some of these qualities, hardness, longevity, lather, etc..
The answer is yes. BUT. 50% olive oil alone won't deliver those qualities. To formulate such a bar, you would need to play around with other fatty acids aiming for an
INS 160 (so-called "perfect soap"). If using no animal fats, it would technically be a "castile" but NOT a "bastile" according to the description above.
The
Basic Trinity of Oils starter formula is a good place to start.
See SoapCalc Printout of
Ed's Bayberry Soap PDF.. INS 157
HAPPY SOAPING!
BASIC TRINITY OF OILS SOAP - INS 157
NOTE:
Soap Bar Quality is well within the recommended Ranges and well balanced.