My recipe calls for coconut oil and lard, but I have adapted it for lard and tallow using SoapCalc 9 wp. The sugar should help give you more sudsing. You might try a small batch of this.
Lard 16 oz.
Beef Tallow 16 oz.
Lye 4.3 oz
Distilled water 12 oz.
Borax 3 Tbsp.
Sugar 1/4 cup
Ammonia 1/4 cup
8 drops Vitamin E
Add sugar and borax to lye water and stir until lye and other ingredients are dissolved. This may take a while.
Melt tallow and lard, stir in Vitamin E. Add lye water and
soap as usual. At thin trace add ammonia. Be careful to soap by an open window because the fumes from the ammonia are potent at first. If desired, you may add 1 oz orange or lemon essential oils.
Pour into mold and let set for 24 hours.