Lye baked goods should not be baked directly on aluminium trays. Fresh lye has a strong corrosive effect on aluminium, so that a critical amount of aluminium can be transferred to the baked goods. In Bavaria, the aluminium content must not exceed a maximum value of 10 mg/kg fresh weight. Otherwise, the food (lye baked goods) is judged unsafe and is not suitable for consumption, as increased aluminium content in food can lead to health problems. As an alternative, baking paper or baking foil can be used as well as coated stainless steel or aluminium trays.
The use of glass fabric on aluminium sheets to prevent direct contact of lye baked goods with the sheet is seen as critical. In this case, lye may come into contact with the aluminium sheet. The use of separating agents (e.g. grease) is not recommended either, as this can transfer a soapy taste to the baked goods. When using paper or foil, there is always poorer heat transfer, which may cause cracks on the sides and bottom of the baked goods. When using baking paper or foil, avoid puddles of lye.
