A Certificate of Analysis (COA) for a white pigment looks like a short table, but each line answers a practical question: how much pigment is in the bag, how much binder it will soak up, whether it will disperse to a smooth film, and how strongly it whitens a tint. This guide walks through the lines on the manufacturer's COA for the rutile grade we supply, KEMOX RC-822 from KMML, so a buyer in a paint, coating, ink or masterbatch plant knows what to look at when a batch arrives.
Supreme Petro Chemicals is a Chennai bulk supplier and distributor, not a manufacturer. The limits quoted below belong to the maker's COA (technical data sheet SPC-TDS-PWD-011). The explanations of what each test means are general knowledge, labelled as such, and the test method your own laboratory uses should always be agreed with the supplier.
The KMML KEMOX RC-822 COA at a glance
| Parameter | Unit | Limit on the COA | What it mainly tells you (general knowledge) |
|---|---|---|---|
| Titanium dioxide (TiO2) | % | 93.0 min | Active pigment content |
| Rutile content | % | 99.0 min | Share of the rutile crystal form |
| Loss on drying (110 C, 1 hr) | % | 1.0 max | Moisture and volatiles |
| Mass tone | - | Close match to standard | Colour of the pigment in a vehicle against a reference |
| pH of 10% aqueous slurry | - | 5.0 to 8.5 | Surface chemistry; compatibility with the system |
| Oil absorption | g/100g | 23.0 max | Binder demand |
| Hegman fineness | - | 6.0 to 8.0 | Dispersion fineness; coarse particles |
| Reducing strength | % | 95 to 110 | Tinting strength against a standard |
| Residue on 325 mesh | % | 0.2 max | Coarse oversize particles |
Source: manufacturer's Certificate of Analysis for KMML KEMOX RC-822, reproduced on SPC-TDS-PWD-011. The limits are the KMML COA limits. The right-hand column is general knowledge, not an SPC specification.
TiO2 content and rutile content: what is actually in the bag
The headline number on the COA is TiO2 content, 93.0% minimum for this grade. The COA does not state what makes up the balance; ask the maker for the datasheet if your process is sensitive to specific components, and state the requirement in your enquiry. The second line, rutile content at 99.0% minimum, is a different measurement: it says how much of the titanium dioxide is in the rutile crystal form rather than anatase. General knowledge, not an SPC specification: rutile is generally preferred where outdoor durability matters, and this is the line that confirms the crystal form.
Do not compare TiO2 percentages across grades blindly
General knowledge, not an SPC specification: two pigments with different TiO2 percentages can perform differently in a formulation for reasons that have nothing to do with the headline number, such as particle size distribution and the dispersion route. Use the percentage to plan the pigment loading, then confirm performance in your own trial.
Loss on drying: moisture matters in powders and masterbatch
Loss on drying (1.0% maximum after one hour at 110 C, per the KMML COA) estimates the moisture and other volatile matter in the powder. General knowledge, not an SPC specification: in a water-based paint a little moisture rarely matters, while in plastics and masterbatch, where the compound is processed at high temperature, residual moisture can show up as bubbles, streaks or voids, so masterbatch makers pay close attention to it. Keep the bags closed and dry: the safety data sheet's storage advice is to keep the product dry and in closed packs, and a bag left open in a humid store will pick up moisture and no longer represent the COA.
Oil absorption: how much binder the pigment demands
Oil absorption is expressed as grams of oil per 100 g of pigment; the COA limit is 23.0 g/100g maximum. General knowledge, not an SPC specification: it measures how much liquid is needed to wet the pigment surface and turn the powder into a coherent paste. A lower number means the pigment needs less binder to wet out, which leaves more room in the formulation for resin or for other fillers. For high-pigment-volume systems, oil absorption is one of the first numbers a formulator looks at, because it moves the pigment volume concentration and therefore the finished film's properties.
Because oil absorption is measured with a specified oil and procedure, a figure from one laboratory's method is not automatically comparable with another's. If you compare two quotes, compare them on the same method.
Hegman fineness: the grind gauge reading
General knowledge, not an SPC specification: Hegman fineness comes from a grind gauge, a steel block with a tapered groove. A pigment dispersion is drawn down along the groove and the point where coarse particles or streaks first appear is read off the scale, which runs from 0 (coarse) to 8 (fine). The COA range for this grade is 6.0 to 8.0. A higher reading means finer dispersion, which supports gloss and smooth films in coatings. Hegman is a measure of dispersion in a given vehicle after a given grinding effort, so it depends on how the pigment was dispersed as well as on the pigment itself. Poor dispersion practice can give a lower reading from a good pigment.
Reducing strength: how strongly the pigment whitens a tint
Reducing strength (the COA limit is 95 to 110%) compares the pigment with a standard when it is mixed with a coloured tint paste. General knowledge, not an SPC specification: a pigment at 100% matches the standard; a pigment at 110% whitens a tint more strongly, and one at 95% less strongly. This is the number to check if you tint whites or pastel shades, because a lower value means you need more pigment to reach the same shade. The COA allows a window rather than a single value because batches vary, and it is a good reason to keep the batch COA with your production records.
Mass tone
Mass tone is reported on the COA as a close match to standard. General knowledge, not an SPC specification: it is the colour of the undiluted pigment dispersed in a vehicle compared with a reference, a quick check on undertone. Because it is a visual comparison against a standard, treat it as a pass/fail on the COA rather than a figure to optimise.
Residue on 325 mesh: the oversize particles
Residue on a 325 mesh sieve (0.2% maximum per the COA) is the fraction of material coarser than the sieve aperture. General knowledge, not an SPC specification: a 325 mesh aperture is roughly 45 micrometres, and oversize particles are the ones that show up as grit, specks or poor surface in thin films and as filter blockages in masterbatch and ink lines. A low residue is a good sign; it complements the Hegman reading, which also reacts to coarse particles but through a different test.
pH of the slurry
A 10% slurry of the pigment in water is measured for pH (5.0 to 8.5 on the COA). The safety data sheet describes titanium dioxide as insoluble in water. General knowledge, not an SPC specification: for an insoluble powder this reading reflects the pigment surface and any soluble residues rather than a solution pH. Check it if your system is sensitive to acidity or alkalinity, for example when the pigment goes into a latex stabilised in a narrow pH window.
A practical incoming-inspection routine
- Check that the grade name, CAS number (13463-67-7) and batch number on the bag match the batch Certificate of Analysis.
- Compare each COA line with the limit above: TiO2 and rutile content first, then the dispersion and strength lines.
- Run your own quick tests on the lines that matter to your process, such as Hegman and reducing strength against your reference sample.
- Hold the batch before release if any line is outside its limit.
- Record the batch COA with the production batch for traceability.
Safety and handling reminders
The safety data sheet for the rutile grade carries a GHS08 Health Hazard pictogram, signal word WARNING, and a Carcinogenicity Category 2 classification by inhalation of respirable dust (H351). When opening bags and charging pigment, minimise dust, use local exhaust or enclosed handling, and follow the current SDS.
What this COA does not tell you
The COA lists nine parameters. It does not state particle size, brightness, density, surface treatment or shelf life; if you need those, ask in your enquiry and state them in your purchase specification. It also does not say that the grade is suitable for food, pharma or cosmetic use: it is a technical pigment grade. Read our companion guide on technical pigment grade versus food, pharma and cosmetic titanium dioxide if your end use is regulated.
Related reading
For the sourcing overview, including the difference between rutile and anatase and applications by industry, see our titanium dioxide supplier guide.
Ask for the TDS and a quote
Send your application, required TiO2 content, quantity and destination to Sanketh on +91 86087 80096 or through the contact page. We quote within 4 working hours, and a batch Certificate of Analysis is supplied with every delivery. See the rutile titanium dioxide product page for the full specification table, documents and pack details.