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What Does KIT Level Mean in Greaseproof Paper? KIT 3 vs KIT 5 vs KIT 7 Explained

2026-08-26

How to Specify Greaseproof Paper for Food Packaging: KIT, GSM, Temperature & Contact Time

An RFQ that says “40 GSM greaseproof paper, KIT 7” sounds precise. In practice, it can still leave the most important performance risks undefined. The same paper can behave very differently when it wraps a warm pastry for ten minutes, a burger with sauce during delivery, or fried food held in a closed takeaway box. Grease load, temperature, contact time, folds, printing and the final packaging format all change the real challenge.

For food packaging buyers, KIT level and GSM are useful specifications, but neither should be selected in isolation. A better approach is to define the application first, then build a paper specification around the conditions the material actually needs to survive.

Buyer takeaway

A useful greaseproof paper specification is not “highest KIT + highest GSM.” It is the lowest practical specification that consistently passes the real food, temperature, hold-time and converting conditions required by the application.

Key Takeaways

KIT level measures grease resistance under a defined test; it does not directly specify paper weight, heat resistance, moisture resistance or real-use hold time.
GSM describes basis weight and influences handling, flexibility and mechanical support, but it does not automatically determine grease resistance.
Temperature, contact time, sauce or moisture, folds and converting can change real packaging performance even when the laboratory KIT result is unchanged.
PFAS-free status is a separate chemical/compliance question. A KIT number does not prove whether PFAS are present or absent.
Before a bulk order, validate the selected paper in the final or representative converted format with the actual food and expected use conditions.

1. Why “40 GSM + KIT 7” Is Not a Complete Greaseproof Paper Specification

A buyer normally needs to define several independent performance requirements. Leaving one of them vague can create a paper that looks correct on a TDS but performs poorly on the filling or converting line.

Specification	What It Helps Define	Risk If It Is Missing
Food / grease load	How much oil or fat the paper must resist	Barrier may be under- or over-specified
Temperature	Thermal condition during packing and use	A room-temperature test may not reflect hot-food performance
Contact time	How long grease remains against the paper	Short tests may not reveal staining during delivery or storage
GSM	Basis weight, body, flexibility and part of mechanical performance	Paper may be too light, too stiff or unsuitable for the converting process
KIT target + test method	Grease-repellency target under defined test conditions	Suppliers may quote non-comparable results
Format / converting	Roll, sheet, bag, wrap, folds, print and machine requirements	Creases, printing or winding may change performance
Compliance requirement	Food-contact and market-specific documentation	A technically suitable paper may still be commercially unusable in the destination market

2. What Does the KIT Test Actually Tell You?

The KIT test, commonly associated with TAPPI T 559, uses a series of numbered test solutions from 1 to 12. The solutions become progressively more aggressive, and the highest-numbered solution that the paper resists without failure is reported as the KIT rating. A higher number therefore indicates higher resistance within that test.

What the number does not tell you is equally important. KIT 7 does not mean “seven hours of grease protection,” and it does not automatically mean the paper is suitable for burgers, fried chicken or any other specific food. Real performance depends on the actual food system and packaging conditions.

Technical point buyers should know

TAPPI describes T 559 as a method developed primarily for papers treated with fluorochemical sizing agents and notes that use with film-like barriers or nonfluorochemical treatments should be evaluated. This matters as the market moves toward PFAS-free and alternative barrier systems. When comparing suppliers, confirm the test method used and validate the paper in the actual application rather than treating one KIT number as universal proof of performance.

Technical reference: TAPPI T 559 – Grease resistance test for paper and paperboard

3. KIT 3 vs KIT 5 vs KIT 7: Use Them as Test Targets, Not Food Labels

KIT 3, KIT 5 and KIT 7 can be useful procurement targets, but they should be treated as relative grease-resistance levels rather than universal application grades.

KIT Target	Relative Interpretation	When a Buyer May Investigate It	What Still Needs Validation
KIT 3	Lower resistance among these three levels	Lighter grease exposure or shorter contact conditions	Actual food, hold time, folds and required cleanliness
KIT 5	Intermediate resistance	Moderate grease-contact applications where additional barrier margin is needed	Temperature, sauce/moisture, converted format and delivery time
KIT 7	Higher resistance among these three levels	Stronger grease challenge or when a wider performance margin is required	Longer contact, hot food, crease lines, printing and end-use trial

Important: This table is a sourcing framework, not a universal food-to-KIT chart. Two burgers, pastries or fried-food applications can require different paper because oil content, serving temperature, sauces, wrap geometry and holding time are different.

KIT 3 vs KIT 5 vs KIT 7.png

4. Start With Four Real-Use Stress Factors

Before deciding whether the target should be KIT 3, KIT 5, KIT 7 or another performance level, define the conditions that will challenge the paper.

Factor	Questions for the Buyer	Why It Changes the Specification
Grease / oil load	Is the food relatively dry, moderately oily or heavily greasy? Are sauces or butter involved?	More aggressive grease exposure can require a stronger barrier target.
Temperature	Is the paper used cold, warm or immediately after frying/cooking?	Temperature can change oil mobility, paper interaction and barrier performance.
Contact time	Is contact measured in minutes, a delivery journey, or several hours?	A paper that looks clean after a short contact may stain during a longer hold.
Format / converting	Flat liner, wrap, bag, sheet, printed web or folded pack?	Folds, creases, print coverage and exposed edges can become weak points.

A useful rule is to increase the validation burden as the combination becomes more demanding. Hotter food + more oil + longer contact + tighter folds is a much tougher packaging condition than any one factor considered alone.

5. KIT vs GSM: Two Different Specification Axes

GSM means grams per square metre and describes the basis weight of the paper. KIT describes grease resistance under a defined test. These are separate properties, and one should not be used as a shortcut for the other.

Parameter	Primarily Describes	Does Not Automatically Prove
GSM	Basis weight, body and part of mechanical structure	Grease resistance, heat resistance or food-contact compliance
KIT	Grease repellency under the stated test method	Paper strength, thickness, moisture barrier or real-use hold time
Application trial	Performance under representative food and packaging conditions	A complete material specification or regulatory compliance

Example: a heavier paper can provide more body, but it is not automatically more grease resistant. A lower-GSM paper with the correct grease-resistant structure or treatment may outperform a heavier sheet with an unsuitable barrier.

6. Why a Paper Can Pass the KIT Test but Still Fail in Real Packaging

This is one of the most useful questions for buyers because laboratory ratings and actual packaging failures are not always the same thing.

Failure Situation	Why the KIT Number Alone May Not Predict It
Grease appears after a long delivery time	The test rating does not directly state how many minutes or hours the final package will remain stain-free.
Paper softens around sauces or steam	KIT focuses on grease repellency, not moisture or wet-strength performance.
Leakage appears along folds	Creasing can disturb the paper structure or barrier at the exact point where stress is concentrated.
Printed paper performs differently from plain paper	Ink coverage, drying, surface treatment and converting may change surface behavior.
A PFAS-free grade behaves differently from an older grade with the same KIT claim	The barrier chemistry and test suitability may differ even when the reported numerical target is similar.
Paper runs poorly on the converter	KIT does not describe tensile strength, stiffness, curl, winding, roll edge quality or machine compatibility.

7. PFAS-Free and KIT Level Are Separate Questions

A KIT value is a performance result. It is not a chemical analysis and cannot, by itself, confirm whether a paper is PFAS-free.

If PFAS-free greaseproof paper is required, state that requirement separately in the RFQ and ask for the documentation appropriate to the destination market and the supplier’s claim. For nonfluorochemical barrier systems, also confirm how grease resistance is evaluated and whether the supplier recommends an additional application or permeability test.

Do not use this shortcut

“High KIT = PFAS-free” is incorrect. Performance, chemistry and compliance must be specified and verified separately.

8. How to Validate Greaseproof Paper Before Mass Production

A representative trial is usually more valuable than adding an arbitrary safety margin to the specification. Test the paper under the same conditions that create risk in real use.

Use the actual food whenever possible, or a representative grease system agreed with the supplier.
Test at the expected packing and serving temperature rather than only at room temperature.
Use the final sheet size, wrap pattern, bag construction or representative converted format.
Inspect flat areas, folds, seams and printed zones separately for staining, weakening or leakage.
Hold the pack for the expected real-use duration, including delivery or storage time where relevant.
Check handling strength, curl, tear behavior and machine performance in addition to grease staining.
Approve a written specification and reference sample before repeat or mass production.

Validate Greaseproof Paper Before Mass Production.png

9. A Better RFQ: What to Send Your Greaseproof Paper Supplier

A clear RFQ shortens the sampling cycle and makes supplier quotations easier to compare. The following format can be copied directly into a sourcing request.

RFQ Item	Information to Provide
Application / food	Burger wrap, bakery liner, fried-food liner, bag converting, interleaving, etc.
Food condition	Grease level, sauces/moisture, hot/warm/cold use
Expected contact time	Typical hold or delivery time
GSM	Target GSM and acceptable tolerance if known
Grease-resistance target	Target KIT level and test method, or ask supplier to recommend after application review
PFAS requirement	Yes / no; specify required declaration or test documentation
Color	White / natural brown
Format	Jumbo roll or sheet
Dimensions	Roll width or sheet size; core and OD if relevant
Printing / converting	Printing method, colors, bag making, folding, die-cutting or other process
Destination market	Required food-contact documentation
Quantity	Trial quantity, first order and expected monthly / annual demand

10. Two Buyer Scenarios: Same “Greaseproof Paper,” Different Specifications

Scenario A: Printed Burger Wrapper for Takeaway

The buyer needs a lightweight sheet that folds cleanly, prints well and stays visually clean through a hot-food delivery cycle. In this case, the paper decision should combine GSM, target KIT, food temperature, sauce exposure, hold time, print coverage and fold performance. Choosing KIT 7 only because it is higher does not answer the printing, moisture or delivery-time questions.

Scenario B: Bakery Interleaving or Short-Contact Liner

The buyer may need flexibility, clean separation and moderate grease resistance, but the contact condition is shorter and the packaging is not tightly folded. A lower grease-resistance target may be technically sufficient, depending on the pastry, butter content and hold time. The better decision is to validate the lower-cost candidate rather than automatically buying the highest available KIT.

11. Common Greaseproof Paper Specification Mistakes

Mistake	Why It Creates Risk
Choosing the highest KIT by default	Can add cost or restrict supply without improving real-use performance.
Selecting by food name only	The same food can have different oil, sauce, temperature and delivery conditions.
Assuming higher GSM means higher grease resistance	Basis weight and grease barrier are separate properties.
Requesting only “food-grade greaseproof paper”	The phrase does not define a measurable barrier or converting requirement.
Treating KIT as proof of PFAS-free status	Chemical status must be verified separately.
Testing only a flat sheet	Folds, printing, seams and converted formats may reveal different failure points.
Ignoring the test method	Two quoted values are not necessarily comparable if the procedure or acceptance criteria differ.

FAQ

Is KIT 7 always better than KIT 5?

KIT 7 represents a higher grease-resistance level within the test, but “better” depends on the application. If KIT 5 already passes the actual food, temperature, contact time and converted-format trial, moving higher may not create a meaningful commercial benefit.

Does KIT 7 mean the paper is PFAS-free?

No. KIT is a grease-resistance performance result. PFAS-free status needs separate supplier documentation or testing appropriate to the claim and destination market.

Does higher GSM mean a higher KIT level?

No. GSM measures basis weight, while KIT measures grease resistance under a defined test. They should be specified independently.

Is the KIT test enough for hot fried food?

Not by itself. Hot, oily food can also challenge moisture resistance, wet strength, folds and hold-time performance. Use representative application testing before bulk purchasing.

Can printing and folding affect grease resistance?

Yes. Printing, creasing, folding and converting can change the surface or create stress points. For critical applications, test the finished or representative converted material.

What information should I provide before asking for a quote?

At minimum: food/application, GSM or current sample, target grease resistance or test method, temperature, contact time, roll/sheet dimensions, printing/converting requirements, PFAS requirement, destination-market compliance needs and expected quantity.

Conclusion: Specify the Application, Not Just the Paper

The most reliable greaseproof paper specification connects laboratory performance with real packaging conditions. KIT level is useful, GSM is useful, and compliance documentation is essential—but none of them works as a complete specification alone.

A practical sourcing formula is: Food & Grease Load + Temperature + Contact Time + GSM + KIT / Test Method + PFAS Requirement + Converting Format + Market Compliance.

For Sure Paper’s greaseproof paper range, 30–50 GSM is the main basis-weight window for food wrapping applications. Final grease-resistance target, color, roll or sheet format and converting requirements should be confirmed against the actual application before mass production.

If you are sourcing greaseproof paper, send us the application, contact conditions, target GSM or current sample, required format and destination market. We can use that information to narrow the suitable paper grade, prepare a representative sample and reduce unnecessary specification changes before the first bulk order.

Explore the product: Food Grade Greaseproof Paper – Sure Paper