I can get tallow for less than 15 cents an ounce delivered from Soaper’s Choice (30 lb cube). OO from Costco is the cheapest I can find and it’s 21 cents an ounce including the tax, but not including the cost of membership, my time or gas costs to get to the store which is 45 minutes away. 3% is the final superfat I aim for. Depending on the planned design and type(s) of colorants, I could be adding extra oil to a recipe calculated at 2% SF or using batch oils to mix the colorants for a recipe calculated at 3% SF. I don’t sweat it too much because there are many sources of error when it comes to calculating superfat, e.g. the real sap value of the fat vs. what’s in the calculator, lye purity, age of my lye masterbatch, scraping the bowl, etc. I keep my methods as consistent as possible, achieve consistent results and feel confident that the final SF is relatively low.
ETA: As an aside, I love lard soap and would use more of it except that when I use it at 50% or more I can start to smell it as the soap ages. It hasn’t been noticeable in the lard + tallow recipe so I thought I would try inching the lard percentage up a little to see what happens. I am also trying slightly higher calculated s+p because I think the tallow I get from SC is a bit on the soft side.
ETA2: From Tisserand & Young’s book Essential Oil Safety (2nd ed, page 584) “Unoxidized limonene, tested at 2% or 3%, was allergenic in 17/8,997 (0.2%) of dermatitis patients.” The percentage was 2% (101/5,116) for oxidized limonene. (Sweet) orange and grapefruit oil are in the range of 84-96% d-limonene, while the percentage in expressed and distilled lemon oil is lower (56-76%).