A paper data sheet gives a grease resistance rating of "KIT 8". A competing quote says "KIT 10" for a cheaper sheet. Does the second paper hold out burger fat better? Not necessarily. The KIT test, the usual grease resistance test for food papers, measures one property, surface oil repellency, under one set of conditions. Used well, KIT ratings are a fast, repeatable way to screen papers; used alone, they can steer a chain towards a wrap that stains in delivery. Below: how the test works, how to read the 1-12 scale, which other tests fill the gaps, and how to write a specification for custom printed greaseproof paper that reflects real food.
What is the KIT test for grease resistance?
The KIT test is a standard laboratory method that rates how well a paper surface repels oil, using twelve numbered test solutions of increasing aggressiveness. The KIT rating is the highest-numbered solution that does not stain the paper within the test time. It is published as TAPPI T559 and as ISO 16532-2.
The method was developed in the paper industry to check papers treated with fluorochemical grease repellents, which work by lowering surface energy so oil beads up instead of wetting the sheet. "KIT" refers to the set of test solutions (a kit), not an acronym. Because it is quick and needs little equipment, it became the default grease resistance figure on data sheets for greaseproof and grease-resistant papers, including today's fluorine-free grades.
How is the KIT test performed?
A drop of each test solution is placed on a conditioned paper sample, left for about 15 seconds, wiped off, and the spot is inspected for darkening. The tester works up the series until a solution causes failure; the last solution that passes gives the rating.
In outline:
- Samples are conditioned at a standard atmosphere (typically 23 °C and 50 % relative humidity) before testing, because moisture content affects results.
- The tester starts with a mid-range solution and moves up or down depending on whether it passes.
- Each drop is released gently onto the sample surface, allowed to stand for the specified time, then removed with clean tissue or cotton.
- A pass means no darkening of the paper under the drop area. Any visible darkening (the oil has wetted or entered the sheet) is a fail.
- Several specimens are tested and the result is reported as the highest passing solution, often with a note on which face was tested.
What do the twelve KIT solutions contain?
The solutions are mixtures of castor oil, toluene and heptane. Kit 1 is pure castor oil, a thick, slow-wetting oil. Each higher number replaces castor oil with more toluene and heptane, which have lower surface tension and viscosity and wet paper far more easily.
| KIT solution | Castor oil (% by volume) | Toluene (% by volume) | n-Heptane (% by volume) |
|---|---|---|---|
| 1 | 100 | 0 | 0 |
| 2 | 90 | 5 | 5 |
| 3 | 80 | 10 | 10 |
| 4 | 70 | 15 | 15 |
| 5 | 60 | 20 | 20 |
| 6 | 50 | 25 | 25 |
| 7 | 40 | 30 | 30 |
| 8 | 30 | 35 | 35 |
| 9 | 20 | 40 | 40 |
| 10 | 10 | 45 | 45 |
| 11 | 0 | 50 | 50 |
| 12 | 0 | 45 | 55 |
Solution proportions are as published in the TAPPI method; the current edition of TAPPI T559 or ISO 16532-2 should be used for any formal testing.
How do you read a KIT rating?
Higher is better: a paper rated KIT 10 repels a more aggressive test liquid than one rated KIT 5. A rating of 0 or 1 means the paper offers little surface oil repellency. Ratings in the upper half of the scale are typical for papers sold as greaseproof or grease-resistant wraps.
Indicative interpretation (supplier conventions vary, so treat this as orientation rather than a standard):
| KIT range | What it suggests | Typical fit |
|---|---|---|
| 0-2 | Little surface oil repellency | Dry products, tray mats where grease is incidental |
| 3-5 | Moderate repellency | Pastries, cookies, cold sandwiches, light deli use |
| 6-8 | Good repellency | Burgers, fried chicken, fries baskets eaten soon after serving |
| 9-12 | High repellency | Very greasy foods, fish and chips, longer holding or delivery times (with food trials) |
A rating is a property of a specific paper face under specific conditions. When comparing data sheets, check:
- Which face was tested (coated face, felt side, wire side) and whether that is the food-contact face of your wrap
- Whether samples were flat or creased
- Conditioning atmosphere and number of specimens
- Whether the figure is a typical value, a minimum, or a single batch result
What does the KIT test not tell you?
KIT measures how quickly oil-like liquids wet the surface at room temperature in seconds. It does not measure how long hot fat takes to soak through the sheet, how the barrier behaves at a fold, or how the paper copes with steam and water. Those are often what decides whether a wrapped burger stains.
The main gaps, and why they matter for wraps:
- Time and temperature: food fats at serving temperature are thinner than at room temperature, and a burger sits in its wrap for minutes, not 15 seconds.
- Creases and folds: wrapping cracks coatings and stresses fibres at the fold line. Flat-sheet KIT values can be noticeably higher than creased performance.
- Mechanism: true greaseproof paper resists oil through a dense, low-porosity structure rather than low surface energy. Two papers with similar real-world holdout can show different KIT numbers, and a surface-treated paper can score well on KIT while letting oil through over time.
- Water: KIT says nothing about steam, sauces or condensation. A paper with a high KIT can still go soft and weak when wet.
- Pinholes: a paper can pass KIT drops in most places yet have isolated voids that leak.
For these reasons, KIT is best used as a screening and batch-consistency check, alongside the tests below and a trial on the actual food.
Greaseproof vs grease-resistant: what is the difference?
In trade use, greaseproof paper gets its oil holdout from the sheet itself: heavily refined, dense fibre with very little open pore space. Grease-resistant paper is usually a lighter, more open sheet made oil resistant by a coating or surface treatment. Neither name is a test result, and neither guarantees a KIT value.
The difference shows up in exactly the gaps listed above. A structural greaseproof sheet tends to keep its holdout at folds and over time, but may score lower on KIT than its real performance suggests. A surface-treated grease-resistant paper can score well on KIT yet lose holdout where a fold cracks the treatment. Some suppliers also use "grease-resistant" for any paper with a KIT value above a stated minimum. Treat both terms as descriptions, then specify the KIT minimum, a creased-sample check and a food trial. The material differences are compared in greaseproof vs parchment vs wax paper.
Which other grease and water tests are used?
The ISO 16532 series covers three grease resistance methods: permeability (Part 1), the KIT surface repellency test (Part 2) and the turpentine test for voids (Part 3). Water absorption is measured separately with the Cobb test, and many buyers add a food simulation trial.
| Test | Standard | What it measures | Why it matters for wraps |
|---|---|---|---|
| KIT (surface repellency) | TAPPI T559, ISO 16532-2 | Highest test solution not wetting the surface | Fast screening; batch-to-batch consistency |
| Permeability test | ISO 16532-1 | Whether and how quickly grease penetrates through the sheet over time | Closer to real holding conditions |
| Turpentine test | ISO 16532-3 (also TAPPI T454) | Time for turpentine to pass through voids in greaseproof and glassine papers | Detects pinholes and weak spots in true greaseproof |
| Cobb water absorption | ISO 535, TAPPI T441 | Grams of water absorbed per square metre in a set time (for example Cobb60 = 60 seconds) | Saucy, steamy or wet foods; lower is better |
| Creased-sample testing | Applied with the methods above on folded specimens | Barrier performance at fold lines | Wraps are always folded |
| Food or oil simulation trial | Internal or agreed method | Staining on the real product at serving temperature over the real holding time | The most relevant result for a chain |
Reading Cobb values
Cobb is reported in g/m² with the test time, for example "Cobb60: 20 g/m²". A lower number means the paper absorbs less water. Uncoated papers absorb water quickly; coated grease-resistant papers can achieve much lower values. For a burger wrap that sees steam from a bun, or a kebab wrap with sauce, a Cobb requirement is as important as the KIT figure. When the food is very wet, a dispersion-coated or PE-laminated wrap may be needed; the options are compared in barrier coatings for paper packaging.
Does a higher KIT number mean PFAS?
No. High KIT values used to be associated with fluorochemical treatments, but fluorine-free greaseproof papers and barrier coatings now reach mid-to-high KIT ratings. KIT measures performance, not chemistry, so PFAS-free status has to be confirmed separately.
In the EU, Regulation (EU) 2025/40 (the PPWR) has restricted PFAS in food-contact packaging since 12 August 2026, including a 50 ppm limit for all PFAS, polymeric PFAS included. In the US, PFAS grease-proofing agents are no longer sold for food contact following the FDA's 2024 announcement, and many states ban intentionally added PFAS in food packaging. Ask for a no-intentionally-added-PFAS statement and total fluorine test data alongside the KIT value. The rules and testing are covered in PFAS-free food packaging.
How should a wrap specification use KIT?
Set a minimum KIT value for the food-contact face, state the test method and whether it applies to flat or creased samples, add a Cobb limit if the food is wet, and require a food trial on the real product before approving a new paper. Then use KIT as the routine check on each delivery.
A practical specification block for a printed burger wrap might read:
| Parameter | Example entry | Notes |
|---|---|---|
| Material | Fluorine-free greaseproof paper, white | Or coated grease-resistant, if agreed |
| Grammage | 35 gsm ± supplier tolerance | Confirm tolerance at quotation |
| Grease resistance | KIT ≥ agreed value, TAPPI T559 / ISO 16532-2, food-contact face | Add "creased" if tested on folded samples |
| Water absorption | Cobb60 ≤ agreed value, ISO 535 | Only where wet foods or steam are involved |
| Food trial | No visible strike-through after agreed time at serving temperature, product X | Define the product and holding time |
| PFAS | No intentionally added PFAS; within PPWR limits, including 50 ppm for all PFAS including polymeric PFAS (EU) / state threshold (US) | Supported by test report; total fluorine data where requested |
| Documentation | Declaration of Compliance, test reports per batch or per agreed frequency | See food-contact guide |
The values themselves depend on the food, the paper type and the supplier's test practice, and are agreed during technical review rather than copied from another chain's spec. Food-contact documentation expectations are summarised in food-contact packaging compliance.
Setting up a simple in-house food trial
A short trial with the real menu item answers the question KIT cannot: will this wrap stain or soften in your operation? It needs no laboratory, only consistent conditions.
- Wrap the product exactly as staff will, using the target fold
- Hold it under realistic conditions: on a pass, in a bag, or in a delivery box, for the longest realistic time
- Unwrap at set intervals (for example 5, 10 and 20 minutes) and photograph the inside and outside of the wrap
- Score visible strike-through on the outer face, softening, and tearing at folds
- Repeat with each candidate paper on the same day, with the same batch of food
Compare results alongside KIT and Cobb figures. If the best-performing paper in the trial is not the one with the highest KIT, trust the trial. For material choices behind the results, see greaseproof vs parchment vs wax paper vs deli paper; for bag formats facing the same question, see grease-resistant food bags.
Next step
When requesting printed wraps, give the food, holding time and any existing KIT or Cobb figures you use, and ask for the supplier's test method and face tested. The custom printed greaseproof paper page lists the full wrap brief, or send your specification for technical review.