The process of making a Vegetable Stone is similar to that of making a spagyric tincture, as previously described. However, instead of having the option of disposing of the plant residue, or salt, you must calcine it and keep it for future use in order to make a Plant Stone. If the salt you obtained from the plant matter is insufficient in volume because you did not use a large amount of herb, you may substitute sea salt. In the event that you need more salt, you can burn dry herb of the same plant used to make the tincture, reduce its ashes to a fine gray-white or white powder, and add them to the salt of the original tincture. However, be clear on this: if the tincture is lemon balm and there is insufficient salt after calcining the plant residue to begin working on a Stone, then you can reduce more lemon balm to an ash without having to make it into a tincture first, because it is the ash, or salt, you want, and not the sulphur. You should not substitute other plants, as they will differ in their planetary signatures, thereby affecting the outcome of the experiment.