Probably the chemical mordant most often used by home dyers is alum, partly because it is effective and readily available and partly because it is much less toxic than other metal mordants. Alum, as its name suggests, is an aluminum compound, packaged as a white powder. But it is possible to obtain mordanting effects from aluminum objects that are commonly found in most households.
Dye manuals will tell you to choose a neutral material such as glass or stainless steel as a dyepot. That is because containers made from other metals will affect the color of the dye. It is possible, however, to utilize that property, if you know in advance the sort of interaction that can be expected. Therefore, let’s say you want to dye wool yellow using goldenrod. In place of the alum recommended in most recipes, you can use an aluminum pasta kettle with no other mordant. The addition of cream of tartar to mitigate harshness in the wool, as in standard recipes, is also a good idea. Aluminum foil, drink cans, TV dinner trays, and pie plates are other possibilities. You probably will have to experiment a bit. As always, it’s best not to cook again with pots and other utensils that have been used for dyeing.