The most reliable homemade dish soap is a bar made from high or full coconut oil at zero percent superfat, because coconut cleans hard and zero superfat leaves no oily film on your plates. Rub a wet brush or sponge across the bar and wash as normal. A pourable version means making soft soap from scratch with potassium hydroxide, not grating a bar into water, which only turns to slime.
I have made dish soap both ways for my own kitchen for years, and the honest truth is that homemade soap cleans dishes well but behaves differently from the blue bottle, because that bottle is not soap at all.
Why my homemade dish soap is a bar
Store dish soap is a detergent, a blend of synthetic surfactants, while a homemade version is true soap made from fat and lye. That difference is not a technicality, it decides how your dish soap performs at the sink.
My first attempt was the popular trick of grating a castile bar into hot water for a liquid. It separated overnight into a snotty, watery gel that clogged the pump and barely touched grease, and I poured a whole wasted bar down the drain. I switched to a coconut oil bar and never looked back. For dish soap, use high or full coconut oil at 0 percent superfat, so no unsaponified oil is left on your dishes.
Coconut oil soap is intensely cleansing and lathers even in hard water, which is why it suits dishes where a gentle skin soap would not. The same trait makes it drying on hands, so a dish bar is deliberately formulated the opposite way from a body bar.
Once you accept that you are making soap and not copying a detergent, the choices fall into place. You maximize cleansing, cut the superfat to nothing, and manage the one weakness soap has that detergent does not: hard water.
What making dish soap really involves
Homemade dish soap means formulating soap for maximum grease-cutting instead of skin comfort. A bar uses sodium hydroxide, while a liquid or soft soap uses potassium hydroxide, which makes a paste you dilute. Both start from the same reaction, just with different lye.
The formulation flips the usual rules. Where a body bar carries a 5 percent superfat for gentleness, a dish bar runs at zero, because any leftover oil would smear onto your dishes. Coconut oil at high percentages gives the bubbles and cleansing power, and citric acid or a chelator like tetrasodium EDTA gets added to fight the scum that soap forms in hard water.
Have you tried a homemade dish soap that left a cloudy film on your glasses? That is soap scum, the reaction between soap and the calcium and magnesium in hard water, and it is the one problem detergent avoids that soap cannot fully escape.
Core skills are recalculating lye for a zero superfat, working with high coconut percentages, and adjusting for citric acid, which consumes a little lye. The craft suits an intermediate soaper comfortable with formulation, and a liquid version suits someone ready to work with potassium hydroxide. Did your grated-bar liquid turn to snot? That is what grated soap does in water. And did a vinegar-and-soap mix curdle into white clumps? The acid broke the soap apart.
Compared to a body soap, a dish bar trades all its skin-conditioning qualities for cleaning power. It will get your dishes clean and sudsy, but the suds fade faster than a detergent’s, and in very hard water you will want a rinse step that store soap does not require.
Essential materials and tools
Here is what a dish bar or liquid needs. Costs are approximate United States retail as of mid 2026.
| Item category | Specifications |
|---|---|
| Coconut oil | 76 degree, at 80 to 100 percent of oils. The cleansing workhorse. 8 to 14 dollars per pound. |
| Sodium hydroxide | NaOH for a solid dish bar, calculated at 0 percent superfat. 8 to 15 dollars. |
| Potassium hydroxide | KOH for a liquid or soft soap, about 40 percent more than NaOH for the same oils. 10 to 18 dollars. |
| Citric acid | Reduces hard-water scum. Consumes a little lye, so add the extra your calculator specifies. 5 to 10 dollars. |
| Tetrasodium EDTA (optional) | Chelator that further cuts scum, near 0.5 percent. 8 to 15 dollars. |
| Mold | Silicone loaf or cavity for bars. Puck shapes suit a dish brush. 10 to 25 dollars. |
| Dish brush or sponge | To load soap from the bar. A brush lasts longer than a sponge. 5 to 12 dollars. |
| Scale and safety gear | 0.1 gram scale, goggles, gloves, stick blender. 55 to 90 dollars combined. |
Do not just drop to zero superfat without recalculating everything. A zero superfat bar has no margin for a weighing error, so measure the lye and oils precisely, and add the extra lye your calculator asks for when you include citric acid.
To get the lye right for a high-coconut recipe at zero superfat, and to account for citric acid, run the full recipe through a lye calculator rather than reusing a body-soap number.
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Key techniques and skills
Work these in order. Formulation and hard-water management do most of the work.
- Formulating for cleansing: build on 80 to 100 percent coconut oil for grease-cutting lather.
- Setting zero superfat: calculate lye with no discount so no oil remains on dishes.
- Adjusting for citric acid: add the extra lye your calculator specifies to offset what the acid consumes.
- Making a bar: soap by cold or hot process, pour, cure, and cut into brush-friendly shapes.
- Making a liquid: cook a potassium hydroxide paste, then dilute it with hot water to your preferred thickness.
- Adding a chelator: stir in tetrasodium EDTA if your water is very hard and scum persists.
- Curing the bar: rack 4 to 6 weeks so it hardens and lasts longer at the sink.
- Loading the brush: rub a wet brush or sponge on the bar rather than squeezing from a bottle.
- Rinsing hard water: finish with a separate vinegar rinse to clear any film.
- Storing the bar: keep it on a draining dish so it dries between uses.
Add citric acid to the recipe and keep a diluted vinegar rinse by the sink. The citric acid cuts scum as you wash and the vinegar clears what remains, which together solve the hard-water film that makes most people give up on homemade dish soap.
Common mistakes and how to avoid them
Each of these has tripped me or my students.
- Grating a bar into water for liquid. Grated bar soap separates into slime, so make liquid soap from scratch with potassium hydroxide instead. The grated shortcut does not hold together.
- Mixing vinegar into the soap. Never mix vinegar into soap; the acid curdles it into white clumps. Use vinegar only as a separate rinse.
- Using a body-soap superfat. A 5 percent superfat leaves oil on dishes. Formulate a dish bar at 0 percent.
- Expecting detergent performance. Homemade soap suds fade and cut grease less aggressively. Judge it as soap, not as the blue bottle.
- Ignoring hard water. Soap forms scum with calcium and magnesium. Add citric acid and rinse with vinegar.
- Forgetting the citric acid lye adjustment. Citric acid consumes lye, which can leave the bar oily. Add the extra lye your calculator gives.
- Using low-coconut recipes. Soft-oil bars barely clean dishes. Keep coconut high for cleansing power.
Handle both sodium and potassium hydroxide with full care, since a dish soap is still lye soap. Add lye to water in a ventilated space, wear goggles and gloves, and remember that a zero superfat recipe leaves no cushion, so accuracy is not optional. The caustic step is the same hazard whether the soap is for skin or dishes.
Bar, liquid, or grated: which route works
Three approaches circulate online, and they are not equally reliable. Knowing which actually holds up saves a wasted batch.
The coconut oil bar is the route I trust. It is simple to make, cleans dishes well, lasts a long time as a hard bar, and pairs naturally with a dish brush. Zero superfat and high coconut give it the cleansing power dishes need, and it stores easily on a soap dish.
The grated-bar liquid is the one to avoid. It is the most shared dish soap idea online and the least dependable, because grated soap dissolved in water separates into a stringy, watery mess that clogs pumps and cleans poorly, no matter how carefully you follow the ratios.
A proper liquid soap made from scratch with potassium hydroxide is the real path to a pourable product. It takes more effort, cooking a paste and diluting it, but it stays stable and pumps cleanly. Choose the bar for simplicity and the from-scratch liquid if you want a bottle, and skip the grated shortcut entirely.
For a costing view, a high-coconut dish bar is cheap per wash once you buy coconut oil in bulk, so weigh the ingredient cost against store detergent before deciding it is worth your time.
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Final thoughts
Homemade dish soap is worth making if you want to cut plastic bottles and know exactly what is in it, as long as you go in expecting soap rather than a detergent clone. Make a high-coconut bar at zero superfat, add citric acid for hard water, keep a vinegar rinse nearby, and rub it onto a brush. If you want a bottle, make liquid soap from scratch rather than grating a bar.
What I would tell a newcomer is that the blue bottle set an expectation soap cannot fully meet, and that is fine once you know it. My dishes come out clean, my hands stay out of synthetic surfactants, and the only trade is a quick vinegar rinse on the days my hard water insists on it.
