As has been noted previously on this blog, Lotus Rock cookware is a metal utensil safe product: stainless steel spatulas, knives and forks can be used on it without damaging the coating. In addition, a Lotus Rock pan can be scrubbed hard with a standard abrasive pad for cleaning without impairing the quality of the pan’s coating. The interior coating for all Lotus Rock pans has been tested and passed, by an independent testing authority, according to BS 7069 Abrasion and Scratch resistance testing standards.
However, although during cooking the interior coating of a pan does undoubtedly have to withstand a high degree of scratching from numerous kitchen utensils, what is not considered as much is the resistance to scratching of a pan’s exterior coating. When using some pots and pans for cooking, such as a stir wok or a crepe pan, it is often necessary to move them quite quickly to get ingredients around the pan or out onto some kind of serving dish. But if this is done over a cooking top surface such as a gas stove, with its sharp protruding edges, the exterior coating of a cookware utensil will, in all likelihood, need to withstand some heavy scratching. If the exterior coating is too soft or thin then these scratches will not only worsen the appearance of the pan quite considerably, but they might also expose the metal substrate beneath the coating to corrosion
A Pencil Hardness test has been used by the kitchenware industry for many years to determine the scratch hardness for the exterior coating of a pan. This test uses special pencils with different degrees of hardness to scratch the coating, which then determines its hardness.
A complete set will have the following pencil gradings, starting with the hardest — 9H, 8H, 7H, 6H, 5H, 4H, 3H, 2H, F, HB, B, 2B, 3B, 4B, 5B, 6B, 7B, 8B and 9B (the latter is the softest pencil; it contains the most graphite and the least amount of clay). The “H” stands for “hardness” and the “B” stands for “blackness,” which comes from the amount of graphite used in the softer pencils.
The simplicity of the pencil hardness test is its great advantage. The special pencils used for doing the test are made of various combinations of graphite and clays, baked in ovens to harden their compositions. By adjusting the amounts of these two organic materials, the pencils are either very soft or quite hard.
BS EN 12983-1-2000+AC:2008 Pencil Hardness Test Procedure
The Pencil Hardness Test procedure, according to BS EN 12983-1-2000+AC:2008, is as follows:
Step 1 = Set up apparatus with a 5H lead loaded to either 4 N or 8 N + 0,2 N.
Step 2 = Draw the apparatus across 25mm of an untouched area of the test surface.
Step 3 = If the lead has cut a clean path through the coating, repeats steps 1 & 2 reducing the grade of the lead by one step each time until it fails to cut a clean path through to the substrate.
Step 4 = Report the hardness of the coating as the hardness of the first lead which failed to cut a clean path through to the substrate.
Generally, even with the stricter standard of a fixed pressure of 8.0 Newtons (765g±2%) applied to the exterior coating, a Lotus Rock pan can pass a Pencil Hardness test with a standard of at least 8H hardness. In fact, more often than not, even if a Lotus Rock pan’s outer coating is scratched a bit from the sharp edges of a gas stove, the surface can still be scrubbed with a standard abrasive pad and the scratch will in most cases be removed. This excellent scratch resistance allows a Lotus Rock pan to be used for a much longer period of time, than say a non-stick coated pan, most of which only have a thin, silicone polyester coating on the outside of the pan. For a standard pencil hardness test, without any heat applied to the surface, then a silicone polyester coating can pass at a 4H hardness standard. If, however, the ambient temperature test is included whereby the surface temperature of the pan is increased to 200 degrees, then a silicone polyester coating is liable to become quite soft, and will then only pass a 2H hardness standard. To counter this problem some manufacturers use a sol gel technology ceramic coating instead of a silicone polyester coating, which is usually twice as thick, with a stronger bonded construction. However, even this type of coating can only reach a 6H hardness standard, still below the Lotus Rock scratch resistant quality of 8H.