Cleansing Yellow is NOT part of our 20-colour eggshell dye kit as it is NOT used to colour your eggshell. Instead it's used to help wash back some of the stronger colours to allow for new lighter dye colours to "take" on the egg.
If you want to wash your egg back to yellow before another yellow or gold dye, or would rather have a yellow base to your following dyes, then dip your dark dyed egg into Cleansing Yellow. You may need to experiment to find out what works best for your egg. Some customers dip into Cleansing Orange and then into Cleansing Yellow to get the more yellow base.
It's good practice to put the cleansing yellow in a plastic container with lid to keep on hand and to make sure it looks different than the eggshell dyes so you can keep them separate. Washing back darker dyes will change the colour of this yellow over time, as it will slowly get contaminated with the darker dyes. Because of this, replace this cleansing yellow when necessary.