How to Write a Graphite Purchase Specification: A Practical Guide for Industrial Buyers

Many quality problems in graphite purchasing do not start with the material. They start with the specification.

A purchase order that says only “flake graphite, 95% carbon, 200 mesh” leaves a great deal open to interpretation. Is 95% a minimum or a typical value? Which test method applies? Does “200 mesh” mean all material passes a 200-mesh sieve, or only most of it? What happens if one shipment arrives slightly outside the limit?

When these questions are not answered in writing, buyer and supplier may each be working to a different understanding of the same product. Both can act in good faith, and the material can still fail in production.

This guide explains how to write a clear graphite purchase specification: what to include, how to define each parameter, and how to turn the specification into a practical tool for supplier approval, incoming inspection and long-term supply.

Quick answer: A graphite purchase specification is the agreed technical document that defines what a supplier must deliver and what the buyer will accept. It should state the product type and grade, fixed carbon as a minimum limit, maximum ash and moisture, particle size (sieve size, passing or retained, and percentage), any critical impurity limits, the test method for each parameter, sampling and COA requirements, packaging, and how deviations will be handled.

Key takeaways

• Write limits, not single values: “fixed carbon ≥ 94%”, not “94% carbon”.

• Define particle size precisely: sieve aperture in µm, passing or retained, and the percentage.

• Every limit needs an agreed test method and reporting basis.

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• Require batch-specific COAs linked to the lot number on the packaging.

• Base the specification on your application, not on a supplier’s datasheet.

Why a Clear Graphite Specification Matters

A purchase specification is the agreed technical definition of what the supplier must deliver and what the buyer will accept. It serves three purposes:

• Supplier selection: quotations from different suppliers can be compared on the same basis.

• Quality control: both parties have a reference for reviewing the COA and inspecting incoming material.

• Dispute prevention: the handling of deviations is agreed in advance.

A COA is only meaningful when it is compared against a defined specification. If the specification is vague, even a detailed COA cannot tell you whether the material is right for your process. For the other side of this process, see our guide on how to read a natural flake graphite COA.

Start With the Application, Not the Grade Name

Before listing any numbers, define what the graphite needs to do in your process. Grade names and product codes differ between suppliers, so two products with similar names may not behave the same way.

Useful questions to answer first:

• What is the application: refractory bricks, foundry coatings, carburizing, lubricants, friction materials, powder metallurgy or another use?

• Which properties are critical to performance, and which are only secondary?

• Which impurities could affect the final product or process?

• What processing steps will the graphite go through, such as mixing, dispersion, pressing or high-temperature exposure?

The answers determine which parameters belong in the specification and how tight the limits need to be. A specification copied from another application, or from a supplier’s standard datasheet, may include unnecessary requirements while missing the ones that matter. If you are still at the early stage of supplier evaluation, our checklist on what to check before buying natural flake graphite is a useful starting point.

1. Product Type and Grade Identification

Start by stating clearly what material is being purchased:

• Product type: natural flake graphite, amorphous graphite, expandable graphite, high-purity graphite, micro-powder graphite, graphite carburizer, etc.

• Natural or synthetic, where relevant.

• The supplier’s grade code and your internal material code.

This sounds basic, but it prevents substitution problems. A specification for “graphite powder” without a product type could, in principle, be met by materials with very different structures and properties.

2. Carbon Content: Define the Limit and the Basis

Fixed carbon is usually the main grading parameter for natural flake graphite. When specifying it, define:

• The limit type: state a minimum, for example “Fixed carbon: ≥ 94%”. Avoid a single value such as “94%”, which can be read as typical, nominal or guaranteed.

• The test method: reference the analytical method agreed with the supplier.

• The reporting basis: dry basis or as-received, where this affects the result.

Choose the carbon level based on the application rather than assuming higher is always better. A higher fixed carbon grade may cost more without improving performance in your process. Our article Is Higher Fixed Carbon Always Better? covers this in more detail.

3. Ash, Moisture and Volatile Matter

These parameters are usually specified as maximum limits:

• Ash: maximum percentage. Ash is a total value and does not identify individual elements.

• Moisture: maximum percentage. Define where it is measured: at the supplier before shipment, or at your site after arrival. Moisture can change during storage and sea transport.

• Volatile matter: include it only if it matters for your process, and specify the test method.

If an application is sensitive to moisture, agree on packaging and storage conditions at the same time (see Section 8).

4. Particle Size and Particle Size Distribution

Particle size is one of the most frequently misunderstood parts of a graphite specification. A mesh number on its own rarely describes the material completely.

Define particle size in a way that can be tested and verified:

• Sieve-based specification: state the sieve size and the required percentage. For example: “+100 mesh (150 µm): ≥ 80% retained” or “−200 mesh (75 µm): ≥ 90% passing”.

• Particle size distribution (PSD): if your process depends on fineness, packing or dispersion, specify D10, D50 and D90 ranges, measured by an agreed method.

• Sieve standard: mesh numbers can vary between standards, so including the aperture size in µm avoids ambiguity.

Writing “200 mesh” without saying whether it refers to passing or retained material, and in what proportion, is one of the most common causes of misunderstanding. See Graphite Mesh Size vs Particle Size Distribution for a fuller explanation.

5. Impurity Limits for Sensitive Applications

If certain elements affect your product or process, list them individually with maximum limits rather than relying on the ash value. Depending on the application, this may include:

• Iron (Fe)

• Sulfur (S)

• Phosphorus (P)

• Silicon (Si) or other elements relevant to your process

In steelmaking and foundry applications, for example, sulfur and phosphorus are commonly controlled because they can affect metal quality. See also our articles on graphite carburizer for gray cast iron and graphite for steel ladle refractories.

For each impurity, state the unit (% or ppm), the maximum limit and the analytical method. For very low limits, confirm that the test method can measure reliably at that level.

Only include impurity limits that are relevant. Adding tight limits for elements that do not affect your process can raise cost and reduce the number of qualified suppliers without improving results.

6. Test Methods and Reporting Basis

A specification limit has little meaning without an agreed way to measure it. Buyers and suppliers often reference recognised standards, for example ASTM C561 for ash in a graphite sample, ISO 3310-1 for test sieves, and ISO 13320 for laser-diffraction particle size analysis, or an equivalent national standard agreed by both parties. Whichever methods you choose, name them in the specification.

For each key parameter, state:

• The test method or standard to be used.

• The reporting basis (dry or as-received), where relevant.

• Which laboratory result prevails in case of disagreement: the supplier’s laboratory, the buyer’s laboratory, or an agreed independent laboratory.

Agreeing on this before the first order is much easier than resolving it after a disputed shipment.

7. Sampling, Batch Definition and COA Requirements

Test results only represent the material if the sample does. Your specification should cover:

• Batch or lot definition: what quantity of production counts as one batch.

• Sampling method: how and where samples are taken.

• COA requirements: which parameters must appear on the COA, and whether it must be batch-specific rather than a typical value.

• Retained samples: whether the supplier keeps a reference sample from each batch, and for how long.

Requiring a batch-specific COA linked to the lot number on the packaging makes incoming inspection and traceability much more straightforward. Batch control is also one of the main reasons graphite performance varies between suppliers even when the specifications look the same.

8. Packaging, Labelling and Storage

Packaging is part of quality, especially for moisture-sensitive or fine materials. Specify:

• Packaging type and net weight, for example 25 kg bags or 1,000 kg jumbo bags, with or without inner liners.

• Palletizing and stacking requirements.

• Labelling: product name, grade, batch number, net weight and production date.

• Any special requirements for moisture protection during sea transport.

Clear labelling also supports the batch traceability described above.

9. Acceptance Criteria and Deviation Handling

Finally, define what happens when results are close to or outside the limits:

• Is every parameter a strict acceptance criterion, or are some for information only?

• Are any tolerances allowed?

• What is the procedure if incoming inspection does not match the COA? For example: re-testing by an agreed laboratory, a joint investigation, or concession and rejection rules.

• What notice is required if the supplier changes raw material sources or processing in a way that could affect the product?

Defining these rules in advance keeps a quality issue from turning into a commercial dispute.

Example: Graphite Purchase Specification Template

The table below shows a typical structure. Values are illustrative only. Set the actual parameters and limits according to your application.

Need an editable version of this template? Contact our team and we will send it to you.

Common Mistakes to Avoid

• Single values instead of limits: “95% carbon” instead of “fixed carbon ≥ 95%”.

• Mesh without direction: “200 mesh” without stating passing or retained, and the percentage.

• No test method: limits that cannot be verified on the same basis by both parties.

• Copying another application’s specification: requirements that do not match your process.

• Over-specifying: unnecessarily tight limits that raise cost without improving performance.

• Ignoring consistency: approving a supplier on one sample without defining batch, sampling and COA requirements for ongoing supply.

How Qingdao Xinghe Graphite Works With Buyer Specifications

At Qingdao Xinghe Graphite Co., Ltd., we supply natural flake graphite and other graphite products for refractory, foundry, lubrication, friction, powder metallurgy and other industrial applications. With integrated mining and processing, we can produce to customer-defined specifications for fixed carbon, particle size and other parameters.

In practice, the most productive starting point is the buyer’s application and current specification. Where a specification is incomplete, we review it with the customer, clarifying limits, test methods and particle size definitions, before samples are prepared. The same agreed specification is then used for sample approval and commercial shipments, which supports consistent quality throughout the supply relationship.

If you are preparing a new graphite specification or reviewing an existing one, send it to our team. We can help check the key parameters and suggest suitable grades for your application.

Frequently Asked Questions

What should a graphite purchase specification include?

At minimum: product type and grade, fixed carbon, ash, moisture, particle size, and the test method for each. Depending on the application, it may also include volatile matter, PSD, specific impurity limits, sampling and batch rules, COA requirements, packaging and deviation handling.

Should I use the supplier’s datasheet as my specification?

A supplier datasheet is a useful starting point, but it describes the supplier’s standard product, not your requirements. Base your specification on your application and agree it with the supplier.

How do I specify particle size for flake graphite?

State the sieve size with the aperture in µm, whether the requirement refers to passing or retained material, and the minimum percentage. If fineness distribution is critical, add D10, D50 and D90 ranges with an agreed measurement method.

How tight should the limits be?

Only as tight as your process requires. Overly tight limits can increase cost and reduce supply options without improving performance. Base limits on application needs and, where possible, on trial results.

Can a supplier produce to a custom specification?

Many manufacturers can, especially those with their own processing capability. Confirm early which parameters can be controlled and what consistency the supplier can maintain across batches.

Conclusion

A clear graphite purchase specification is one of the most effective quality tools a buyer has. It turns general expectations into measurable requirements, makes supplier quotations comparable, and gives both parties a shared reference for COA review and incoming inspection.

The most useful specifications start from the application, define each parameter as a verifiable limit with an agreed test method, and set out how batches, sampling and deviations will be handled. With that foundation in place, the focus moves from a single good sample to what matters most in industrial supply: consistent quality from shipment to shipment.

References

• ASTM C561 – Standard Test Method for Ash in a Graphite Sample, ASTM International: https://store.astm.org/c0561-91r10e01.html

• ISO 3310-1 – Test sieves: Technical requirements and testing, Part 1: Test sieves of metal wire cloth, International Organization for Standardization

• ISO 13320 – Particle size analysis: Laser diffraction methods, International Organization for Standardization