Short answer: Two numbers decide most surfactant formulation problems: CMC, the concentration where micelles start to form, and the Krafft point, the temperature below which solubility collapses. CMC tells you where detergency and foam plateau. The Krafft point tells you whether the product survives winter storage and cold dilution. Both are testable before you commit a tank.
This article is written for formulators who want the numbers behind those two rules of thumb. CMC values are typical literature figures at 25 C in pure water; real formulas shift them through electrolytes, co-surfactants and soil load. Confirm the values that matter in your own system.
What is the CMC, and why does it set your dosage floor?
The critical micelle concentration (CMC) is the point where surfactant molecules stop acting alone and start forming micelles. Detergency, solubilisation of grease and foam stability all jump at the CMC and then improve slowly above it. Below the CMC you are paying for molecules that mostly sit free in water and do much less work.
Sodium lauryl sulfate has a CMC of about 8.2 mM at 25 C, roughly 2.4 g/L in pure water. A dishwashing liquid at 12% active therefore runs at about 50 times its CMC in the concentrate. That sounds wasteful until you look at the use dilution: at 1:50 the product lands near 2.4 g/L, right around the CMC, which is where cleaning actually happens. The concentrate is high because the dilution has to arrive at the CMC, not because more surfactant cleans proportionally more.
What is the Krafft point, and how does it show up in production?
The Krafft point is a temperature, not a concentration. Below it, the surfactant’s solubility falls sharply and micelles cannot form, so the product clouds, gels or throws a precipitate. SDS sits close to room temperature, with published values around 16 C. SLES and AOS are far more soluble and stay clear at temperatures where SDS fails, which is one reason liquid personal care formulas moved to SLES and hard-water detergents moved to AOS.
Typical values for the grades you buy
| Surfactant | CMC at 25 C, typical literature | Krafft point behaviour | What it means in the plant |
|---|---|---|---|
| SLS / SDS (CAS 151-21-3) | About 8.2 mM (roughly 2.4 g/L) | Around 16 C, published range roughly 15-20 C | Clouds in cold water and winter transit; store above 20 C |
| SLES (CAS 68585-34-2) | Roughly 0.1-1.0 mM, varies with ethoxylation and alkyl chain | Well below room temperature | No cold-clouding problem in normal storage |
| AOS (CAS 68439-57-6) | Low millimolar range; confirm on the TDS | Below room temperature | Liquids pump and dose reliably in cold seasons |
| LDS (CAS 2044-56-6) | Same order as SDS, single-digit mM | Below SDS; soluble at 0-4 C | The cold-room and winter-logistics grade |
Treat the CMC column as orientation, not specification. Salt lowers the CMC, which helps cost per kilogram of cleaning but tightens the viscosity window; co-surfactants such as betaine lower it further. The Krafft column is the one to verify by test, because purity and alkyl distribution move it.
How do you use the CMC when setting dosage?
Work from the use dilution backwards. Decide the dilution ratio your customer applies, set the target concentration at that dilution to land at or just above the CMC, then multiply up to the concentrate. A worked case for a general cleaner at 1:100 dilution with SLS at 2.4 g/L CMC: the concentrate needs at least 240 g/L, or 24% active, to arrive at the CMC in use. Anything below that under-performs at the bucket; anything far above mostly buys foam.
The same arithmetic explains why high-active powders sell. SLS 92% powder and SLS 95% powder deliver the active matter without the freight cost of water, and the cost per kg of active matter calculation shows what that is worth per tonne.
How do you use the Krafft point for winter logistics?
Ask where the product gets cold, not where it is made. A drum of SLS-based concentrate shipped to Russia in January, or stored in an unheated warehouse in Iran, can spend days below the Krafft point and arrive clouded or gelled. Three mitigations that work: specify SLS 30% liquid or AOS liquids instead of high-active concentrates, store and ship above 20 C where the route allows, and write a cold-settling recovery step into the QC protocol rather than rejecting a cloudy drum on sight. Our articles on freezing and clouding in winter and stopping products from freezing cover the failure cases in detail.
Quick checks before you blame the surfactant
- Viscosity jump: salt sensitivity, not a CMC problem. The salt thickening mystery explains the non-linear response.
- Clouding at the tap: hardness plus a sulfate ester, which points to AOS or SLES rather than more dosage.
- Separation in storage: emulsion or hydrotrope stability, which is a different troubleshooting tree.
- Foam that will not build: check the use dilution against the CMC before adding surfactant.
Key takeaways
- CMC sets the dosage floor: below it, surfactant does little; far above it, you buy foam rather than cleaning.
- Krafft point sets the temperature ceiling for failure: SDS clouds near 16 C; SLES, AOS and LDS tolerate more cold.
- Salt lowers the CMC: helpful for cost, risky for viscosity control.
- Design backwards from the bucket: land the use dilution at or just above the CMC, then size the concentrate.
- Test both numbers on your formula: literature values are a starting point, not a specification.
Frequently asked questions
What is the CMC of SLS in water?
About 8.2 mM at 25 C, which works out to roughly 2.4 g/L for sodium lauryl sulfate with a molecular weight of 288.38. Electrolytes and co-surfactants in a real formula push the effective value down, sometimes by a factor of two or more.
Why does my product cloud in winter?
The most common cause is the Krafft point. When temperature drops below it, solubility falls and the surfactant comes out of solution as a cloud or a gel. SDS-based concentrates are the usual suspects; SLES, AOS and LDS grades tolerate more cold. Warm the product back above the Krafft point and it usually clears.
Does adding salt change the CMC?
Yes. Electrolytes compress the electrical double layer around the micelle and lower the CMC, so a salted formula micellises at a lower surfactant concentration. That helps cleaning per kilogram but narrows the salt-thickening window, which is why viscosity can jump unexpectedly when the salt level moves.
Is a higher active content always better value?
Not by itself. Higher active content means less freight per kilogram of active matter, but past the point where the use dilution clears the CMC, the extra surfactant buys foam and viscosity. Value comes from matching active content to the dilution ratio and the cost per kg of active matter, not from maximising assay.
How do I test the Krafft point of my surfactant?
Prepare a 1% solution, cool it slowly in a temperature-controlled bath, and record the temperature at which cloudiness appears on heating back up. Compare grades under the same protocol. For purchasing decisions, ask the supplier for the Krafft point or solubility data on the TDS and verify it on a retained sample.
Request a quote or a sample
For bulk pricing, MOQ and lead time on SLS 92%, SLS 95%, SLS 30% liquid, AOS 35%, AOS 38% or LDS, request a quote. If you are qualifying a grade for a winter route or a cold-room protocol, request a sample and request the COA and MSDS with solubility data for the lot. Contact our team with your destination and storage conditions and we will recommend the grade that fits.
Written and reviewed by the ORID Chem technical team. Last updated: 25 October 2026. CMC and Krafft point values are typical literature figures, not guaranteed specifications. Confirm current specifications on the product TDS and lot COA before ordering.
