There are some glaze ingredients that are volatile during a firing, even in a cone 5 electric kiln, and will evaporate and travel around the kiln. These pieces make use of that, with a glaze where the volatile colourant is removed from the recipe and placed nearby in the kiln to give a flash of colour during the firing.
I then made a very basic chrome wash by mixing equal parts Chromium Oxide and Gerstley Borate with water, and applied this fairly thickly to the top of test tiles.
They were arranged in the kiln like so:
The same technique works with copper to a lesser extent. It works much more effectively on glazes with reasonably high tin content (5%, and upwards). The easiest way to start with it is to do as I did above, and remove the chrome or copper from a glaze recipe and place it nearby for a flash of the colour. It will produce interesting effects on other glazes though, so it's worth experimenting with a range of glazes (with or without tin) to see what you get.
That's all there is to it! Please try it and let me know how you get on, message me or use the hashtag oldforgecreations (I often miss @mentions on Instagram and there's no way to find them afterwards, but I'll see the tag). Good luck!