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Specify the barrier, not the weight\u2014that’s how you stop leaks before they reach customers.<\/strong><\/p>\n\n\n\n Food service operators and procurement managers sourcing delivery packaging will gain clarity on specification gaps here, preparing them for the detailed menu-matching guidance that follows.<\/p>\n\n\n\n ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~<\/p>\n\n\n\n The delivery driver calls. Another complaint. Grease leaked through the bag onto a customer’s leather car seat. The wrapper looked fine when it left the kitchen\u2014but somewhere between handoff and arrival, the damage was done.<\/p>\n\n\n\n This scenario plays out daily in food service operations everywhere. The instinct is almost always the same: order thicker paper next time. Heavier stock. More substantial bags. The logic feels solid.<\/p>\n\n\n\n Except it doesn’t work.<\/p>\n\n\n\n Grease Resistance Ratings, measured by Kit Levels on a standardized 1\u201312 scale, define a paper’s ability to repel oil and grease for a specific duration. This is fundamentally different from paper weight or thickness. Generic ‘brown paper’ fails not because it’s too thin, but because it lacks the chemical barrier that Kit-treated greaseproof paper<\/a> provides.<\/p>\n\n\n\n Kit Levels function as a performance threshold: a higher number protects against intense exposure (hot fryer oil), while a lower number suffices for lighter exposure (pastries). The number tells you how long the barrier holds under specific grease and heat conditions\u2014not how heavy the paper feels in your hand.<\/p>\n\n\n\n Understanding this distinction transforms how you specify food packaging. It stops the leak before it reaches your customer.<\/p>\n\n\n\n Kit Levels measure how well paper resists penetration by oils and greases under controlled test conditions\u2014not how thick or heavy the paper is.<\/p>\n\n\n\n The Kit test (TAPPI T 559)<\/a> applies a series of increasingly aggressive solvent mixtures to paper samples. The highest-numbered mixture that the paper successfully repels for a set time determines its Kit Level rating. A Kit 1 rating indicates minimal grease resistance; Kit 12 represents the highest protection against aggressive oils and fats.<\/p>\n\n\n\n The Kit number represents how aggressive a grease the paper can block\u2014independent of the material’s basis weight or total duration of exposure in non-standardized environments.<\/p>\n\n\n\n A common mistake is assuming higher Kit numbers mean the paper is universally “better.” A Kit 12 paper designed for fried chicken would be overengineered and overpriced for wrapping a croissant. The goal isn’t to maximize the number. Match the number to your actual menu conditions.<\/p>\n\n\n\n Paper basis weight, measured in GSM (grams per square meter), tells you about the material’s mass and density, which generally correlates with stiffness. Thickness, or caliper, is measured separately in microns or mils\u2014but crucially, neither metric dictates grease resistance (TAPPI T 410<\/a> & TAPPI T 411<\/a>). It says nothing about the chemical barrier.<\/p>\n\n\n\n You can have a heavy 80 GSM paper that leaks grease in minutes and a lighter 45 GSM paper with a Kit 8 rating that holds up through a 20-minute delivery window. The confusion between weight and performance leads to wasted purchasing decisions. Operations teams order heavier paper expecting better protection, pay more, and still receive complaints.<\/p>\n\n\n\n The specification that actually matters\u2014Kit Level\u2014never appears on the purchase order. For foundational context on how these specifications relate, see food packaging paper specifications 101<\/a>.<\/p>\n\n\n\n Thicker paper still leaks because grease doesn’t care about thickness. It cares about finding a path through.<\/p>\n\n\n\n Untreated paper consists of a highly porous web of fibers, which is why sourcing from greaseproof paper mills<\/a> that apply proper barrier treatments is essential for food service applications. While cellulose itself is naturally hydrophilic (water-attracting) and fundamentally lipophobic, the physical structure of the paper is the true vulnerability. When grease contacts the surface, powerful capillary action pulls the lipids directly through the interstitial air spaces between the fibers. The porous network acts like a sponge, drawing oil deeper into the material. Over time, grease migrates to the other side and stains whatever it touches: hands, clothes, car seats, branded packaging.<\/p>\n\n\n\n This mechanism explains why simply adding weight doesn’t solve the problem. More fibers still create more pathways for grease to travel\u2014unless those fibers have been chemically treated to repel oil.<\/p>\n\n\n\n The physics matter for operations planning. A wrapper might look perfectly clean when food is packaged. The grease migration is happening, but it hasn’t reached the outer surface yet.<\/p>\n\n\n\n Add a 15-minute delivery window, and suddenly the wrapper that “worked fine” in the kitchen fails catastrophically in the customer’s hands. This is why hold time is such a critical variable. Paper performing adequately for immediate consumption can fail completely when food sits longer\u2014in a delivery bag, in a warming drawer, or on a customer’s desk waiting to be eaten.<\/p>\n\n\n\n Grease stains don’t appear the moment food touches paper. They appear after grease has had time to migrate through untreated fiber.<\/p>\n\n\n\n This creates a frustrating pattern: everything looks fine in the kitchen, complaints arrive later, and the connection to paper specification isn’t obvious. The customer doesn’t know your paper lacks a chemical barrier. They see a grease stain and draw conclusions about your food quality, your brand, and your attention to detail.<\/p>\n\n\n\n The decision rule is straightforward: match Kit Level to the combination of fat content, food temperature, and how long the paper must perform.<\/p>\n\n\n\n Higher fat content requires higher Kit protection. Higher temperature accelerates grease migration. Longer hold times give grease more opportunity to penetrate. All three variables interact. Mismatching any of them causes failure.<\/p>\n\n\n\n Fat content<\/strong> is the most obvious factor. A heavily greased fried chicken thigh presents a more aggressive challenge than a lightly buttered croissant. The grease load\u2014how much oil actively presses against the paper surface\u2014determines the baseline Kit requirement.<\/p>\n\n\n\n Temperature<\/strong> accelerates everything. Hot grease is more fluid and penetrates faster than cooler grease. Food coming straight off a fryer at 355 – 375\u00b0F (180 – 190 \u00b0C) attacks paper barriers more aggressively than room-temperature items.<\/p>\n\n\n\n Hold time<\/strong> determines how long the barrier must function. A wrapper performing for the 3 minutes between kitchen and counter might fail completely over a 25-minute delivery window\u2014a critical consideration when sourcing wrapping paper<\/a> for delivery-focused operations.<\/p>\n\n\n\n Delivery and extended hold times are where most grease failures manifest. Paper that served dine-in customers adequately for years suddenly generates complaints when delivery volumes increase.<\/p>\n\n\n\n This isn’t the paper getting worse. The conditions are getting more demanding. A 5-minute hold time becomes a 20-minute hold time, and the Kit Level that barely cleared the first threshold has no chance at the second.<\/p>\n\n\n\n The practical implication: expanding delivery or hold-and-serve operations may require revisiting paper specifications\u2014even if the paper itself hasn’t changed.<\/p>\n\n\n\n Use this reference to match common menu items to appropriate Kit Level ranges. The table accounts for typical fat content, serving temperature, and standard hold times.<\/p>\n\n\n\n
\n\n\n\nWhat Grease Resistance Ratings (Kit Levels) Actually Measure<\/h2>\n\n\n
![\"\u201cGrease](\"https:\/\/www.paperindex.com\/academy\/wp-content\/uploads\/2026\/02\/grease-resistance-kit-test-procedure.png\")
<\/figure>\n<\/div>\n\n\nWhy the Scale Measures Performance, Not Thickness<\/strong><\/h3>\n\n\n\n
\n\n\n\nWhy “Thicker Paper” Still Leaks: The Failure Mechanism<\/h2>\n\n\n\n
Density and Capillary Wicking During Hold Time<\/strong><\/h3>\n\n\n\n
Why Leaks Appear at the Worst Moment<\/strong><\/h3>\n\n\n\n
\n\n\n\nOperational Alignment: Matching Kit Level to Variable Exposure<\/h2>\n\n\n\n
![\"\u201cGrease](\"https:\/\/www.paperindex.com\/academy\/wp-content\/uploads\/2026\/02\/grease-resistance-rating-decision-process-1024x581.png\")
<\/figure>\n\n\n\nThe Three Inputs That Matter<\/strong><\/h3>\n\n\n\n
The Tipping Point: When “Fine” Becomes Failure<\/strong><\/h3>\n\n\n\n
\n\n\n\nMenu-to-Kit Matching Table<\/h2>\n\n\n\n