A previous blog post described how a migration test can be done to test the surface reactivity of a cookware pan. The benefit of a non-stick coating on a pan is that it contains a substance called PTFE, which has very low reactivity with substances in contact with it. Even to this day, PTFE has been proven to have the lowest coefficient of friction (CoF) of any known solid. In other words, the majority of materials do not stick to it. Therefore, because of its excellent non-stick release and low reactivity to substances in contact with it, a PTFE-based non-stick coating should pass a standard BS EN 1186-1: 2002 migration test quite easily.
However, although PTFE does undoubtedly provide excellent non-stick release and low reactivity for a coating on a cookware utensil, it does have some significant disadvantages; one of these is a tendency of a PTFE-based non-stick coating to peel off. Within a non-stick coating PTFE does not bond well to itself, which means it can have a pinhole problem. This difficulty can be exacerbated not only through general scratching with a utensil and rubbing with a cleaning pad, but also when oil is heated on a pan to a high temperature for high heat cooking methods, such as stir frying or sautéing etc. For these types of high heat cooking methods, the molecules of cooking oil can decrease in size quite rapidly and then penetrate the highly porous PTFE coating. This can lead to the coating breaking up and peeling off – thus not only impairing the quality of the non-stick release but also creating a safety hazard as bits of the coating mix with the food on the pan.
One method to determine the resistance of non-stick coatings to separation from substrates, such as aluminum or steel, is to utilize a tool by cutting a right angle lattice pattern into the coating, penetrating all the way to the substrate. This is called the Cross Cut Adhesion Test, otherwise known as ISO 2409-2013. Some coatings may have a multi-layer system, and so this test can also be used to determine the resistance to separation of different layers from one another.
The below table are the classification of test results for an ISO 2409-2013 Cross Cut Adhesion Test.
An ISO 2409-2013 test was conducted by SGS testing services, from 16th January 2015 to 21st January 2015, on a Lotus Rock frying pan. The test result was as follows.
As you can see from the results above and the photos of the tested samples below, a Lotus Rock pan got a perfect score of 0; the edges of the cuts are completely smooth, and none of the squares of the lattice are detached. This excellent result is in part due to the fact that the coating on a Lotus Rock pan is not a standard PTFE based coating. All Lotus Rock pans have a very thick ceramic layer, up to 100 microns thick, on top of the heavy gauge carbon steel substrate. Nestled on top of the ceramic layer is a very thin silicon-oxide crystal coating which is so thin that it is very difficult for a utensil or other piece of equirement to dettach it from the ceramic layer below it. Therefore unlike a weakly bonded and thinly coated PTFE based coating, a Lotus Rock pan can, with its strongly constructed coating, be cooked on for an extended period of time without any fear that the coating will peel off or break up.