Standard hydrogenated castor oil (HCO) usually has a melting point in the mid-80s °C and a hydroxyl value of roughly 155 to 165 mg KOH/g. A low iodine value, typically a few units at most, shows the oil has been fully hydrogenated.
These are typical commercial ranges, not a standard. Plants publish slightly different bands, so agree exact limits in your specification and confirm them on your own samples.
What each figure tells you
- Melting point shows how hard and pure the wax is; a low result can mean incomplete hydrogenation or other fats mixed in.
- Hydroxyl value shows how many hydroxyl groups survived hydrogenation; a low result means some were lost, often from too much heat.
- Iodine value shows remaining double bonds; a high result means hydrogenation was incomplete.
- Acid value shows free fatty acid; it should be low, usually a few units at most.
- Saponification value shows the overall ester content and helps spot contamination.
- Colour shows refining quality and any overheating.
Why hydroxyl value matters most
The hydroxyl group is the reason people buy HCO. During hydrogenation, high temperature can strip some hydroxyl groups off the chain. The result still looks like HCO and may melt correctly, but it performs worse in grease and other uses.
If you make 12-HSA or grease, set a minimum hydroxyl value and test it on every lot. A plant that controls temperature well will meet a tight band without difficulty.
How to test
Melting point is often measured by capillary or drop point methods, and the two give different numbers. State the method in your specification. Hydroxyl value, iodine value and acid value have standard titration methods published by bodies such as AOCS and ISO.
Ask the plant which methods it uses and make sure your lab uses the same ones. Otherwise, a gap of a few degrees or a few units may be a method difference, not a quality problem. Our guide on reading a lab certificate covers this.
Setting your own limits
Start from what your process needs. A grease plant may set a firm minimum hydroxyl value and a tight maximum iodine value, and accept a wider melting range. A cosmetic user may care more about colour, odour and nickel than about a few units of hydroxyl value.
Then compare your draft limits with certificates from two or three good plants. If no plant can meet a limit, it may be too tight. If every plant beats it easily, you may be able to tighten it. Our guide on writing a specification for HCO or 12-HSA puts these limits into a full specification.
Keep a retained sample of the lot you approve. If a later lot performs worse, you can test both side by side.
Next step
We can help you set HCO limits, have samples tested by an independent lab and check each lot before it ships. Book a free sourcing review to start.