Generally, food should not be offered in utensils made of iron; if we cook in vessels made of iron, we have to offer them in another type of vessel. Moreover, Ever Silver is made of iron and it is not considered sacred to offer food in such a vessel. Vessels gilded with silver, brass, or white lead can be used to offer food.
Most importantly, utensils used for Perumal should be exclusive (called ulpathiram) such that it is not used by us.