People either hate these books by Cavitch or they love them,and there's little room in between. Her book is a very valuableresource for technical info on oils/fats and their properties, and for basic ideas for recipes, however, if you follow all of her instructions you are missing out on some basic facts and better ways of doing things (i.e. you do NOT need to use GSE, just don't superfat your soap so dang much; USE a stick blender, the author probably had a batch trace too quickly and/or seize and thus swore off the stick blender; you do NOT need to use oxides nor are they "natural" colorants, they're metal-based and synthesized in labs; don't swear off the use of tallow or lard, and don't rely on the author's stats on them either; don't mistake her saponification table for potassium hydroxide as being one for sodium hydroxide, this will lead to disaster). You don't need to weigh your water either. These aren't serious procedural snafus, but the author obviously picked them up early in her soapmaking and has not let go of them. You will need GSE if you follow her recipes exactly and don't recalculate the lye, because her recipes produce soap that has enough excessive fat to make it go rancid after some months.