Frequently Asked Questions About SoapCalc

SoapCalc can only provide a limited perspective on your question. Thousands of experienced soap makers hang out in online communities and are happy to help newcomers.

The best places to ask questions:

• Soapmaking Forum — The largest dedicated soap making community. Very active, very beginner-friendly. Use the search to find archived discussions on just about any topic: colorants, essential oils, fragrance oils, trace, seizing, orange spots, ash, temperature, lye concentration, specific oils.
• r/soapmaking on Reddit — Active community with recipe feedback, troubleshooting, and photo shares.
• Facebook groups — Search for "soap making" on Facebook. There are several large groups with tens of thousands of members.

When asking for help, mention what process you're using (CP, CPOP, HP, etc.) and share your recipe if you can. You'll get much better answers with specifics.

Yes. Put the milk (or your milk/water solution) where you would put the water in SoapCalc.

If you haven't made soap with milk before, read up on the process first. The procedures are different from making soap with water — you need to handle temperatures more carefully to avoid scorching the milk sugars.

Good starting points:

• Anne Watson's book Milk Soapmaking
• Search "milk soap" on Soapmaking Forum — there are hundreds of threads covering every variation

The "One" column displays the soap qualities and fatty acid percentages of the individual oil you've selected in the center column. As you click on different oils, the numbers change to show that oil's specific profile.

The "All" column displays the combined soap qualities and fatty acid percentages of all the oils in your recipe. These numbers appear after you click Calculate Recipe. If you change an oil or adjust a percentage, click Calculate Recipe again to update the "All" column.

When you hover over each soap quality in SoapCalc (Hardness, Cleansing, Conditioning, etc.), a suggested range of values appears. The same ranges are shown on the graph on the View Recipe page.

These are guidelines, not rules. The possibilities outside these ranges are endless, and some of the best-loved soaps break them entirely.

Two examples:

• 100% lard soap — Scores outside several "ideal" ranges but makes excellent, hard, creamy bars. Traces quickly and can volcano if the fat is too hot, so it requires some experience.
• 100% olive oil soap (Castile) — Hardness, cleansing, and bubbly all score below the suggested ranges. Yet it's one of the most popular soaps in history. It takes much longer to trace and much longer to cure (6+ months for best results).

For a complete explanation, see the Soap Qualities page.

Most soap makers experiment with small 1-pound test batches to see what works. That's the best way to learn what these numbers actually mean for your soap.

There is no single right number. It depends on your recipe, your process, and your experience.

The water in your recipe separates the oils into fatty acids and glycerine (a process called hydrolysis), making them available to react with the lye and form soap. Most, but not all, of the water evaporates during the soap making process.

The default is 38%. It's a safe starting point that will make a decent bar for both cold process and hot process. Beginners should start here.

More experienced soap makers typically reduce this to around 32–33%. You can also set the Lye Concentration or Water : Lye Ratio directly if you prefer those methods.

If you used exactly the amount of lye needed to saponify all the fatty acids in your oils, you'd have zero superfat — no excess oil and (ideally) no excess lye. That's nearly impossible to achieve outside a chemistry lab.

In practice, you discount the lye. A 5% lye discount means you use 5% less lye than theoretically needed. The result: about 95% of the bar is soap, and about 5% is unsaponified oil that conditions your skin. That 5% is your superfat.

A higher superfat (say 8–10%) means more conditioning but a softer bar that may not clean as aggressively. A lower superfat (2–3%) means a harder, more cleansing bar with less conditioning. The default 5% is a good balance between safety and performance.

Because SAP values are averages, not exact numbers.

The SAP value used to calculate your lye amount comes from published data that represents a range. One of our references gives coconut oil a KOH SAP of 250–264. That's a meaningful spread. Why does it vary? Several factors:

• Species of the plant used to make the oil
• Where it was grown
• How the oil was processed
• When the plant was harvested
• Maturity of the plant at harvest

Unless you've had your specific batch of oil assayed in a chemistry lab (and weighed everything on laboratory-grade scales), you don't know the exact SAP value. The 5% discount is a safety margin that accounts for these natural variances, so you don't end up with soap that contains unreacted lye.

It's pure milk fat — not butter, half and half, cream, or heavy cream.

Commercial butter is about 80% butterfat and 15% water. The "milk fat" entry in SoapCalc represents the pure fat only. You can make it at home by clarifying butter over heat (removing the water and milk solids), or use ghee if it's available where you are.

It depends on what's in your shortening. Check the ingredients label and match it:

Most brand-name all-vegetable shortenings follow one of the first two patterns. Check for beef tallow on the label — if it's there, use the Walmart GV entry.

All of these shortenings contain small amounts of mono- and diglycerides, BHA or TBHQ, propyl gallate, and citric acid as antioxidants. The tallow-based Walmart version also contains dimethylpolysiloxane (an anti-foaming agent). In theory, anti-foaming agents could reduce bubbliness, but at about 50% of a recipe we haven't noticed any loss of lather.