When mixing clay for a recipe you will need to weigh the materials.  Most recipes will be in parts of 100 with all parts adding up to 100.  This makes it fairly easy to scale up or down according to your specific needs. You will need a weighing container and a large scale. It is useful when buying materials to label the material in several places on the bag so that it is easy to identify from multiple places on the bag.  Another tip would be to label a piece of paper and put it in the bag so that you are never unsure of what you have. Before starting to work with raw materials, always make sure you put on your respirator.  Weigh your container and add that weight to the final weigh you want to achieve so that you will have accurate measurements.  The easiest way to transfer the material from the bag to your weighing container is with a ladle.   Remember to keep a close eye on the scale when you are weighing material so you don't go over the desired amount, or you will have to remove material.You will need to repeat this process for each material you are weighing for your recipe, crossing each material off your list as you go to avoid confusion.  These are the basic steps to measuring materials for a recipe.