Loss on ignition test for industrial minerals.
Understand the LOI formula, calculate mass loss, select the correct material-specific method and review an LOI result without confusing moisture, structural water, carbon dioxide or organics.
Calculate LOI from measured masses.
Use direct sample masses or full crucible readings. The calculator does not select the test method for you.
Mass inputs
Select the format that matches the laboratory worksheet.
What loss on ignition does and does not show.
LOI is a gravimetric result. It measures net mass change under defined heating conditions, not one specific chemical constituent.
Free and bound water
Depending on the procedure, LOI may include residual moisture and structurally bound water released from hydrated minerals.
Carbon dioxide
Carbonates can release carbon dioxide during decomposition. Therefore, a high LOI can be expected in carbonate-rich material.
Organics and volatiles
Organic matter, processing aids and other volatile species may contribute, subject to the selected temperature and atmosphere.
Not a purity certificate
LOI alone cannot identify mineral phases, contamination or application suitability. Review chemistry, mineralogy and the full specification.
A reviewable LOI test sequence.
The exact quantities and heating conditions belong to the governing standard or agreed procedure. The sequence below shows the control logic.
Confirm the governing method
Identify the material standard, buyer specification, laboratory procedure and reporting basis before preparing the sample.
Prepare a representative test portion
Homogenize and reduce the sample without selectively losing fines, moisture or volatile material.
Prepare and tare the crucible
Use the crucible type required by the method. Clean, condition, cool and weigh it before adding the sample.
Record the initial mass
Weigh the test portion or the crucible-plus-sample reading with the balance resolution required by the procedure.
Ignite under specified conditions
Apply the stated temperature, duration, atmosphere and furnace loading. Avoid spattering, contamination and sample loss.
Cool without moisture uptake
Transfer the crucible according to the laboratory procedure, normally using controlled cooling and a desiccator before weighing.
Reweigh and repeat when required
Some procedures require additional heat-cool-weigh cycles until the mass change falls within a defined constant-mass criterion.
Calculate and report completely
Report the result with method, temperature, duration, basis, sample identity, test date and any deviation from the procedure.
Choose a standard by material and application.
There is no universal LOI temperature for every industrial mineral. The correct method follows the product, market and contractual specification.
| Material or context | Relevant published framework | What the buyer should confirm | Important limitation |
|---|---|---|---|
| Talc pigment | ASTM D605, Standard Specification for Magnesium Silicate Pigment (Talc) | Current edition, test procedure referenced by the specification, sample basis and acceptance limit. | Do not replace the specified method with a generic furnace condition. |
| Limestone, quicklime and hydrated lime | ASTM C25, chemical analysis methods | Material type, sample preparation, exposure controls and the required LOI section. | Quicklime and hydrated lime can absorb water and carbon dioxide from air. |
| Fly ash and natural pozzolan | ASTM C311, sampling and testing procedures | Whether the result is being used for specification compliance and which current edition applies. | LOI does not directly identify carbon content in every ash. |
| Paint extenders | ISO 3262 family and the applicable material-specific part | Exact extender type, current part, test basis and declared limit. | Different extender parts can use different requirements. |
| Buyer-specific mineral grade | Approved internal method or purchase specification | Temperature, time, atmosphere, pre-drying, sample mass, constant-mass rule and laboratory acceptance criteria. | A commercial method must be agreed before quotations or lots are compared. |
Read the value through mineralogy and method.
A high or low number is not automatically good or bad. First determine what the mineral is expected to release under the selected conditions.
| Material | Expected LOI contributors | Useful cross-checks | Buyer caution |
|---|---|---|---|
| Talc | Structural hydroxyl, associated carbonates, serpentine-group minerals, moisture or processing residues. | XRD mineralogy, MgO, CaO, carbonate indicators, moisture and full chemical analysis. | Do not classify cosmetic, polymer or ceramic grade from LOI alone. |
| Calcite-rich material | Mainly carbon dioxide released from carbonate decomposition, plus moisture or organics if present. | CaCO3 or CaO result, carbon dioxide method, mineralogy and moisture. | A high LOI may be normal rather than evidence of contamination. |
| Dolomite-rich material | Carbon dioxide from calcium and magnesium carbonates, plus other volatile components. | CaO, MgO, carbonate mineralogy and thermal profile. | Partial decomposition can occur if the method is not aligned. |
| Kaolin and calcined kaolin | Free moisture, structural water, organics and residual uncalcined material. | XRD, moisture, brightness, calcination status and application tests. | Natural and calcined grades should not share one benchmark. |
| Barite or silica filler | Moisture, organics, associated carbonates or other impurities. | BaSO4 or SiO2 assay, moisture, XRD and contamination review. | Small values require adequate balance resolution and blank control. |
Initial mass = 10.0000 g
Residue mass = 9.5250 g
Mass loss = 0.4750 g
LOI = 4.750%The arithmetic is valid only for the method used to generate those masses.
Ideal talc structural H2O: 4.75%
Ideal calcite CO2: 43.97%
Ideal dolomite CO2: 47.73%
Ideal kaolinite structural H2O: 13.96%These are AHR stoichiometric calculations from ideal mineral formulas. They are not product specifications or universal acceptance limits.
Common causes of unreliable LOI results.
Most disputes come from method mismatch, sample handling or incomplete reporting rather than the percentage calculation itself.
Method mismatch
Different temperatures, times, atmospheres or pre-drying steps can produce different values from the same material.
Moisture exchange
Opened samples can gain or lose moisture. Record storage, conditioning and test timing.
Incomplete ignition
Insufficient time, low temperature, overloaded furnaces or unsuitable crucibles may leave volatile components in the residue.
Sample loss
Spattering, dust escape or transfer loss increases apparent LOI without representing a true volatile component.
Mass gain
Oxidation can increase residue mass and create a low or negative result. Investigate rather than forcing the result to zero.
Reabsorption
Hot or reactive residues can absorb moisture or carbon dioxide during cooling and weighing.
Review the LOI line on a Certificate of Analysis.
A percentage without traceability and test conditions is not enough for a technical approval.
The COA name and grade code match the purchase order, sample and bag label.
The tested lot number matches the supplied shipment or clearly defined production batch.
The current standard, laboratory method or buyer procedure is stated and reviewable.
The ignition conditions are stated, including constant-mass language where applicable.
The document distinguishes as-received, pre-dried or dry-basis reporting.
The result is compared with the approved specification, not an unrelated generic benchmark.
Moisture, chemistry and mineralogy are reviewed when needed to explain the LOI result.
Sampling, testing, issue date and authorized laboratory approval form a credible sequence.
Download the LOI buyer checklist
Export a CSV checklist for supplier document review, pre-shipment approval or laboratory clarification.
Loss on ignition FAQ.
Use these answers when reviewing quotations, specifications and laboratory documents.
What is the loss on ignition formula?
LOI percentage equals initial sample mass minus residue mass, divided by initial sample mass, multiplied by 100. Use the masses defined by the governing method.
Is LOI the same as moisture?
No. Moisture normally measures mass lost under a lower-temperature drying procedure. LOI can include moisture, structural water, carbon dioxide, organics and other volatile components, depending on the method.
What is a good LOI value for talc?
There is no universal value for every talc application. The acceptable result depends on mineralogy, the specified method and the approved grade. Review LOI with XRD, chemistry, moisture and application requirements.
Why must the ignition temperature be reported?
Different components decompose or volatilize at different temperatures. Changing the temperature can change which mass losses are included.
Can LOI be negative?
Yes. A net mass gain can occur through oxidation or contamination. A negative result should trigger a method and quality review rather than being automatically replaced with zero.
Can two supplier COAs be compared directly?
Only when the product basis, method, temperature, time, atmosphere, preparation and reporting basis are equivalent. Otherwise, request aligned testing.
Primary sources used for method control.
Standards are copyrighted and may require purchase. Use the current official edition when a contract or specification depends on them.
Official ASTM scope confirms loss on ignition is one of the specified talc pigment properties.
Official ASTM scope includes a loss-on-ignition section and emphasizes sample exposure control.
Official ASTM scope includes moisture and loss-on-ignition procedures for these materials.
Material-specific extender standards contain relevant specifications and test-method references.
NIST notes that alternative methods may produce different moisture and LOI values and that opened material can change.
USGS data illustrate that talc ores can contain associated minerals and varied LOI values, supporting mineralogical review.
Need a mineral specification or COA reviewed?
Send the product, grade, batch, method, LOI result, supporting chemistry, quantity and destination. AHR can coordinate a document-led review before quotation or shipment.