If your silicone baking mat still feels slick or greasy even after washing it, the problem may not be poor cleaning. Repeated exposure to oils and high temperatures can leave behind a stubborn residue known as polymerised oil.
According to recipe developer Marissa Stevens, repeated heating causes oils and fats to oxidise and bond with the silicone rather than simply remaining on its surface. This can make the mat feel greasy even after dishwasher cycles or soaking in hot, soapy water.
Why the greasy layer develops
Silicone naturally attracts oil, and once oil has been repeatedly heated onto the surface, ordinary dish soap may not be enough to remove it.
For routine cleaning, the mat should be washed after every use with a soft sponge, warm water and soap. It should then be rinsed well and dried completely.
A simple way to deep-clean the mat
For deeper cleaning, Stevens recommends spreading a thin paste of baking soda and water over the mat and leaving it for 15 to 20 minutes. The surface can then be gently scrubbed with a soft brush before being rinsed with a little white vinegar or lemon.
For heavier residue, she suggests placing the mat flat on a baking sheet and heating it in a 350°F oven for 10 to 15 minutes. Wearing oven mitts, the warm mat can then be placed in hot, soapy water to soak. The heat helps loosen the oil, making it easier to scrub away.
Avoid harsh scrubbers
Steel wool and abrasive sides of sponges should be avoided because they can scratch silicone. Scratches may provide more places for grease to collect.
Discolouration is generally cosmetic, but heavy oil buildup can affect food release and allow old smells and flavours to transfer to future bakes. An occasional deep clean can therefore help keep silicone baking mats more effective and longer-lasting.