How many grams is a teaspoon per pound of oils?
Soap additive rates are written the way people measure in a kitchen ("1 tsp PPO", a teaspoon per pound of oils) and weighed out, if at all, on a scale. The step between the two is the density of the powder. A teaspoon is a volume: exactly 4.929 mL in the US. What that volume weighs depends entirely on what's in it, so "1 tsp PPO" means a different percentage for every additive. It is 0.48% of the oils for colloidal oatmeal and 1.54% for honey. This tool converts using a published weight for each one, and tells you how good that weight is.
The supplier rate is 1 tsp per pound of oils. Sodium lactate is sold as a 60% liquid with a density of about 1.33 g/mL, so a US teaspoon of it weighs 1.33 × 4.929 = 6.56 g. Per pound (453.6 g) of oils that's 1.45%, so a 1,000 g batch takes 14.5 g of the liquid, which is 8.7 g of actual sodium lactate. Measured with a teaspoon instead, it would be 1,000 ÷ 453.6 = 2.2 tsp.
Usage rates for common soap additives, in grams
SoapmakingToolbox.com · soap additive usage rates for cold process, per 1,000 g of oils
| Additive | Customary rate (in US tsp) | % of oils | Per 1,000 g oils | 1 tsp weighs | Weight source | Where it goes |
|---|---|---|---|---|---|---|
| Sodium lactate (60% solution) | 0.7–2.1 tsp per lb of oils | 1.01–3.03% | 10.1–30.3 g | 6.6 g | maker spec | Cooled lye water (below ~130 °F), or the oils. No lye adjustment. |
| Granulated sugar | ½–1 tsp per lb of oils | 0.46–0.92% | 4.6–9.2 g | 4.2 g | USDA | Dissolve in the recipe’s water before the lye goes in. |
| Honey | ½–1½ tsp per lb of oils | 0.77–2.31% | 7.7–23.1 g | 7.0 g | USDA | At trace, thinned 1:1 with some of the recipe’s water; soap cool. |
| Table salt (as a hardener) | 1–3 tsp per lb of oils | 1.32–3.97% | 13.2–39.7 g | 6.0 g | USDA | Dissolve in the warm lye water. |
| Kaolin (white) clay | 1 tsp per lb of oils | 0.44% | 4.4 g | 2.0 g | rough (weigh yours) | Disperse 1 tsp in 1 tbsp distilled water; add at trace or to the oils. |
| Bentonite clay | 1 tsp per lb of oils | 0.97% | 9.7 g | 4.4 g | weighed | Disperse in water first — it swells. |
| French green clay | 1 tsp per lb of oils | 0.56% | 5.6 g | 2.5 g | weighed | Disperse 1 tsp in 1 tbsp distilled water. |
| Rose clay | ½–2 tsp per lb of oils | 0.30–1.22% | 3.0–12.2 g | 2.8 g | rough (weigh yours) | Diluted 2–3× with water, into the batter or the lye water. |
| Titanium dioxide | ½–1 tsp per lb of oils | 0.33–0.65% | 3.3–6.5 g | 3.0 g | maker spec | Disperse 1 tsp in 1 tbsp oil (or water); add at trace. |
| Activated charcoal | ⅛–1 tsp per lb of oils | 0.07–0.54% | 0.7–5.4 g | 2.5 g | maker spec | Into the warm oils, stick blended, before the lye. |
| Mica (colorant) | ½–2 tsp per lb of oils | 0.33–1.32% | 3.3–13.2 g | 3.0 g | rough (weigh yours) | Mix 1 tsp in 1 tbsp oil; add at trace. |
| Colloidal oatmeal | 3 tsp per lb of oils | 1.43% | 14.3 g | 2.2 g | rough (weigh yours) | At trace, or into the oils. |
| Whole milk powder | 1½–3 tsp per lb of oils | 0.88–1.76% | 8.8–17.6 g | 2.7 g | USDA | Whisked into some of the oils, added at light trace. |
| Poppy seeds | 1 tsp per lb of soap | 0.92% | 9.2 g | 2.9 g | USDA | At thin trace. |
US level teaspoon (4.929 mL). The rate column is in teaspoons, so tablespoon rates appear ×3, and the sodium lactate range is classicbells' 10–30 g per kilo of fats converted to teaspoons (suppliers give 1 tsp per pound of oils); the tool shows each source as published. "Per lb of soap" rates are restated per pound of oils (× 1.42). Weight sources: USDA FoodData Central portion weights; weighed = published level-spoon weighings; maker spec = manufacturer bulk density; rough = proxy or single report (weigh three level teaspoons of your own and divide by three). Sodium lactate figures are for the 60% liquid.
The sources for every rate and weight are in the tool: pick an additive and it shows both. Four powders people ask about aren't in the table: zinc oxide, coffee grounds, ground oats and silk. For the first three we couldn't find a weight per spoon we'd stand behind (used coffee grounds are wet, and grinding oats changes their density); silk is dosed by the pinch. Weigh a level teaspoon of yours and enter it in the tool's calibration box, and any of them converts the same way.
A level teaspoon of bentonite weighs about 4.4 g; the same spoon of kaolin, about 2.0 g. A chart that lists both as "clay, 1 tsp PPO" gives the bentonite bar 2.2 times as much clay, and bentonite is the one that swells and thickens. Across this table a teaspoon runs from 2.2 g (oatmeal) to 7.0 g (honey). That's why rates in spoons can't be compared with each other, and why weighing is the only way to repeat a bar exactly.
Sodium lactate: how much, and is the rate for the liquid?
For the liquid. Sodium lactate is sold as a 60% solution, and every customary rate (the suppliers' "1 tsp per pound of oils", classicbells' 10–30 g per kilo of fats) is for the solution as it comes out of the bottle. The confusion is in the arithmetic: 1 tsp PPO is sometimes converted to "about 3% of oil weight", but at 6.56 g a teaspoon it is 1.45%, half that. classicbells' range works out to 0.7–2.1 tsp PPO, so the supplier teaspoon sits toward the low end, which is where most people want it: sodium lactate makes bars release from the mold sooner, and too much makes them brittle.
Stir it into the lye water once it has cooled below about 130 °F, or into the oils; it needs no change to the lye. And it's for unmolding, not a cure for a soft recipe. The soft soap guide explains why reaching for it first is treating the wrong problem. If you make your own from lactic acid, that's a different calculation: lactic acid consumes lye, and the citric acid and vinegar calculator handles it.
Per pound of oils, or per pound of soap?
"PPO" is per pound of oils, but not every rate is. Soap Queen gives clay and honey per pound of soap, and a pound of cold-process batter is only about 0.70 lb of oils (the rest is lye and water). So 1 tsp per pound of soap is 1.42 tsp per pound of oils, or 42% more. The tool's "per pound of" switch does the conversion; the table above has already done it for the rates published that way.
A teaspoon of powder, or a teaspoon of the mix?
Titanium dioxide, mica and clays are usually dispersed before they go in: 1 teaspoon of powder in 1 tablespoon of oil or water. Some suppliers' rates refer to the dispersion: "1 tsp per pound" of the mixed slurry, which at 1 part powder to 3 parts liquid is only about a quarter of a teaspoon of powder. A maker who reads that rate as dry powder uses 4 times the titanium dioxide. The result is a chalky, flat white, and any glycerin rivers in the batch show up starkly against it. If a rate doesn't say which, ask the supplier; the tool's dispersion box converts either way.
US, metric and Australian spoons
| Spoons | Teaspoon | Tablespoon | A tablespoon of honey |
|---|---|---|---|
| US | 4.93 mL | 14.79 mL | 21.0 g |
| Metric (UK, EU, NZ, CA) | 5.00 mL | 15.00 mL | 21.3 g |
| Australian | 5.00 mL | 20.00 mL | 28.4 g |
US spoons from NIST Handbook 44 (1 tbsp = ½ US fl oz exactly); honey 7.0 g per US teaspoon (USDA), scaled to each tablespoon by its volume in mL.
Teaspoons are close enough everywhere. The Australian tablespoon is not: at 20 mL it holds 35% more than a US one, so a tablespoon rate from an American blog measured with an Australian spoon overshoots by a third. Weights don't have this problem.
When the published rates disagree
They often do, and a converter is the easiest way to see by how much. Salt as a hardener is "1 tsp PPO" on the soapmaking forum's rate list and "1 tablespoon per pound of oils" elsewhere. That is 1.32% against 3.97% of the oils, a threefold difference. Clay is 1 teaspoon per pound of soap at Soap Queen and 1 tablespoon per pound of soap at Natural Beauty Workshop: per pound of oils, 0.63% and 1.88% of kaolin. Neither is wrong; they're different bars. Start at the low end, write down what you used in grams, and adjust from there.
Powders vary with grind, brand and how they've settled. For anything the table marks "rough" (or any time a bar has to repeat), scoop three level teaspoons of your own powder onto a scale, divide by three, and put that in the tool's calibration box. It overrides the table for that conversion and goes into the share link. Leveled, not packed: a packed teaspoon of clay can weigh half as much again.
What these additives do to the rest of the recipe
None of them change the lye. The acids do, which is why they aren't here. A few change something else a calculator should know about. Sugar and honey heat the batch, pushing it toward gel and, in excess, cracking. The gel phase guide covers managing it, and the milk soap calculator shows that milk already carries a teaspoon of honey's worth of sugar per pound. Milk powder brings fat, which nudges the superfat; the milk calculator works that out too. Salt hardens a bar at a spoonful; at 50–100% of the oils it's a salt bar, and the salt bar calculator takes over, including how little salt lye water can dissolve.